]>
Commit | Line | Data |
---|---|---|
1 | /* | |
2 | * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH) | |
3 | * | |
4 | * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> | |
5 | * | |
6 | * Interactivity improvements by Mike Galbraith | |
7 | * (C) 2007 Mike Galbraith <efault@gmx.de> | |
8 | * | |
9 | * Various enhancements by Dmitry Adamushko. | |
10 | * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com> | |
11 | * | |
12 | * Group scheduling enhancements by Srivatsa Vaddagiri | |
13 | * Copyright IBM Corporation, 2007 | |
14 | * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> | |
15 | * | |
16 | * Scaled math optimizations by Thomas Gleixner | |
17 | * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de> | |
18 | * | |
19 | * Adaptive scheduling granularity, math enhancements by Peter Zijlstra | |
20 | * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> | |
21 | */ | |
22 | ||
23 | #include <linux/latencytop.h> | |
24 | #include <linux/sched.h> | |
25 | #include <linux/cpumask.h> | |
26 | #include <linux/cpuidle.h> | |
27 | #include <linux/slab.h> | |
28 | #include <linux/profile.h> | |
29 | #include <linux/interrupt.h> | |
30 | #include <linux/mempolicy.h> | |
31 | #include <linux/migrate.h> | |
32 | #include <linux/task_work.h> | |
33 | ||
34 | #include <trace/events/sched.h> | |
35 | ||
36 | #include "sched.h" | |
37 | ||
38 | /* | |
39 | * Targeted preemption latency for CPU-bound tasks: | |
40 | * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds) | |
41 | * | |
42 | * NOTE: this latency value is not the same as the concept of | |
43 | * 'timeslice length' - timeslices in CFS are of variable length | |
44 | * and have no persistent notion like in traditional, time-slice | |
45 | * based scheduling concepts. | |
46 | * | |
47 | * (to see the precise effective timeslice length of your workload, | |
48 | * run vmstat and monitor the context-switches (cs) field) | |
49 | */ | |
50 | unsigned int sysctl_sched_latency = 6000000ULL; | |
51 | unsigned int normalized_sysctl_sched_latency = 6000000ULL; | |
52 | ||
53 | /* | |
54 | * The initial- and re-scaling of tunables is configurable | |
55 | * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) | |
56 | * | |
57 | * Options are: | |
58 | * SCHED_TUNABLESCALING_NONE - unscaled, always *1 | |
59 | * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) | |
60 | * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus | |
61 | */ | |
62 | enum sched_tunable_scaling sysctl_sched_tunable_scaling | |
63 | = SCHED_TUNABLESCALING_LOG; | |
64 | ||
65 | /* | |
66 | * Minimal preemption granularity for CPU-bound tasks: | |
67 | * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) | |
68 | */ | |
69 | unsigned int sysctl_sched_min_granularity = 750000ULL; | |
70 | unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; | |
71 | ||
72 | /* | |
73 | * is kept at sysctl_sched_latency / sysctl_sched_min_granularity | |
74 | */ | |
75 | static unsigned int sched_nr_latency = 8; | |
76 | ||
77 | /* | |
78 | * After fork, child runs first. If set to 0 (default) then | |
79 | * parent will (try to) run first. | |
80 | */ | |
81 | unsigned int sysctl_sched_child_runs_first __read_mostly; | |
82 | ||
83 | /* | |
84 | * SCHED_OTHER wake-up granularity. | |
85 | * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) | |
86 | * | |
87 | * This option delays the preemption effects of decoupled workloads | |
88 | * and reduces their over-scheduling. Synchronous workloads will still | |
89 | * have immediate wakeup/sleep latencies. | |
90 | */ | |
91 | unsigned int sysctl_sched_wakeup_granularity = 1000000UL; | |
92 | unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; | |
93 | ||
94 | const_debug unsigned int sysctl_sched_migration_cost = 500000UL; | |
95 | ||
96 | /* | |
97 | * The exponential sliding window over which load is averaged for shares | |
98 | * distribution. | |
99 | * (default: 10msec) | |
100 | */ | |
101 | unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; | |
102 | ||
103 | #ifdef CONFIG_CFS_BANDWIDTH | |
104 | /* | |
105 | * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool | |
106 | * each time a cfs_rq requests quota. | |
107 | * | |
108 | * Note: in the case that the slice exceeds the runtime remaining (either due | |
109 | * to consumption or the quota being specified to be smaller than the slice) | |
110 | * we will always only issue the remaining available time. | |
111 | * | |
112 | * default: 5 msec, units: microseconds | |
113 | */ | |
114 | unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; | |
115 | #endif | |
116 | ||
117 | static inline void update_load_add(struct load_weight *lw, unsigned long inc) | |
118 | { | |
119 | lw->weight += inc; | |
120 | lw->inv_weight = 0; | |
121 | } | |
122 | ||
123 | static inline void update_load_sub(struct load_weight *lw, unsigned long dec) | |
124 | { | |
125 | lw->weight -= dec; | |
126 | lw->inv_weight = 0; | |
127 | } | |
128 | ||
129 | static inline void update_load_set(struct load_weight *lw, unsigned long w) | |
130 | { | |
131 | lw->weight = w; | |
132 | lw->inv_weight = 0; | |
133 | } | |
134 | ||
135 | /* | |
136 | * Increase the granularity value when there are more CPUs, | |
137 | * because with more CPUs the 'effective latency' as visible | |
138 | * to users decreases. But the relationship is not linear, | |
139 | * so pick a second-best guess by going with the log2 of the | |
140 | * number of CPUs. | |
141 | * | |
142 | * This idea comes from the SD scheduler of Con Kolivas: | |
143 | */ | |
144 | static unsigned int get_update_sysctl_factor(void) | |
145 | { | |
146 | unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8); | |
147 | unsigned int factor; | |
148 | ||
149 | switch (sysctl_sched_tunable_scaling) { | |
150 | case SCHED_TUNABLESCALING_NONE: | |
151 | factor = 1; | |
152 | break; | |
153 | case SCHED_TUNABLESCALING_LINEAR: | |
154 | factor = cpus; | |
155 | break; | |
156 | case SCHED_TUNABLESCALING_LOG: | |
157 | default: | |
158 | factor = 1 + ilog2(cpus); | |
159 | break; | |
160 | } | |
161 | ||
162 | return factor; | |
163 | } | |
164 | ||
165 | static void update_sysctl(void) | |
166 | { | |
167 | unsigned int factor = get_update_sysctl_factor(); | |
168 | ||
169 | #define SET_SYSCTL(name) \ | |
170 | (sysctl_##name = (factor) * normalized_sysctl_##name) | |
171 | SET_SYSCTL(sched_min_granularity); | |
172 | SET_SYSCTL(sched_latency); | |
173 | SET_SYSCTL(sched_wakeup_granularity); | |
174 | #undef SET_SYSCTL | |
175 | } | |
176 | ||
177 | void sched_init_granularity(void) | |
178 | { | |
179 | update_sysctl(); | |
180 | } | |
181 | ||
182 | #define WMULT_CONST (~0U) | |
183 | #define WMULT_SHIFT 32 | |
184 | ||
185 | static void __update_inv_weight(struct load_weight *lw) | |
186 | { | |
187 | unsigned long w; | |
188 | ||
189 | if (likely(lw->inv_weight)) | |
190 | return; | |
191 | ||
192 | w = scale_load_down(lw->weight); | |
193 | ||
194 | if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) | |
195 | lw->inv_weight = 1; | |
196 | else if (unlikely(!w)) | |
197 | lw->inv_weight = WMULT_CONST; | |
198 | else | |
199 | lw->inv_weight = WMULT_CONST / w; | |
200 | } | |
201 | ||
202 | /* | |
203 | * delta_exec * weight / lw.weight | |
204 | * OR | |
205 | * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT | |
206 | * | |
207 | * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case | |
208 | * we're guaranteed shift stays positive because inv_weight is guaranteed to | |
209 | * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22. | |
210 | * | |
211 | * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus | |
212 | * weight/lw.weight <= 1, and therefore our shift will also be positive. | |
213 | */ | |
214 | static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw) | |
215 | { | |
216 | u64 fact = scale_load_down(weight); | |
217 | int shift = WMULT_SHIFT; | |
218 | ||
219 | __update_inv_weight(lw); | |
220 | ||
221 | if (unlikely(fact >> 32)) { | |
222 | while (fact >> 32) { | |
223 | fact >>= 1; | |
224 | shift--; | |
225 | } | |
226 | } | |
227 | ||
228 | /* hint to use a 32x32->64 mul */ | |
229 | fact = (u64)(u32)fact * lw->inv_weight; | |
230 | ||
231 | while (fact >> 32) { | |
232 | fact >>= 1; | |
233 | shift--; | |
234 | } | |
235 | ||
236 | return mul_u64_u32_shr(delta_exec, fact, shift); | |
237 | } | |
238 | ||
239 | ||
240 | const struct sched_class fair_sched_class; | |
241 | ||
242 | /************************************************************** | |
243 | * CFS operations on generic schedulable entities: | |
244 | */ | |
245 | ||
246 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
247 | ||
248 | /* cpu runqueue to which this cfs_rq is attached */ | |
249 | static inline struct rq *rq_of(struct cfs_rq *cfs_rq) | |
250 | { | |
251 | return cfs_rq->rq; | |
252 | } | |
253 | ||
254 | /* An entity is a task if it doesn't "own" a runqueue */ | |
255 | #define entity_is_task(se) (!se->my_q) | |
256 | ||
257 | static inline struct task_struct *task_of(struct sched_entity *se) | |
258 | { | |
259 | #ifdef CONFIG_SCHED_DEBUG | |
260 | WARN_ON_ONCE(!entity_is_task(se)); | |
261 | #endif | |
262 | return container_of(se, struct task_struct, se); | |
263 | } | |
264 | ||
265 | /* Walk up scheduling entities hierarchy */ | |
266 | #define for_each_sched_entity(se) \ | |
267 | for (; se; se = se->parent) | |
268 | ||
269 | static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) | |
270 | { | |
271 | return p->se.cfs_rq; | |
272 | } | |
273 | ||
274 | /* runqueue on which this entity is (to be) queued */ | |
275 | static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) | |
276 | { | |
277 | return se->cfs_rq; | |
278 | } | |
279 | ||
280 | /* runqueue "owned" by this group */ | |
281 | static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) | |
282 | { | |
283 | return grp->my_q; | |
284 | } | |
285 | ||
286 | static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, | |
287 | int force_update); | |
288 | ||
289 | static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) | |
290 | { | |
291 | if (!cfs_rq->on_list) { | |
292 | /* | |
293 | * Ensure we either appear before our parent (if already | |
294 | * enqueued) or force our parent to appear after us when it is | |
295 | * enqueued. The fact that we always enqueue bottom-up | |
296 | * reduces this to two cases. | |
297 | */ | |
298 | if (cfs_rq->tg->parent && | |
299 | cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) { | |
300 | list_add_rcu(&cfs_rq->leaf_cfs_rq_list, | |
301 | &rq_of(cfs_rq)->leaf_cfs_rq_list); | |
302 | } else { | |
303 | list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, | |
304 | &rq_of(cfs_rq)->leaf_cfs_rq_list); | |
305 | } | |
306 | ||
307 | cfs_rq->on_list = 1; | |
308 | /* We should have no load, but we need to update last_decay. */ | |
309 | update_cfs_rq_blocked_load(cfs_rq, 0); | |
310 | } | |
311 | } | |
312 | ||
313 | static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) | |
314 | { | |
315 | if (cfs_rq->on_list) { | |
316 | list_del_rcu(&cfs_rq->leaf_cfs_rq_list); | |
317 | cfs_rq->on_list = 0; | |
318 | } | |
319 | } | |
320 | ||
321 | /* Iterate thr' all leaf cfs_rq's on a runqueue */ | |
322 | #define for_each_leaf_cfs_rq(rq, cfs_rq) \ | |
323 | list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list) | |
324 | ||
325 | /* Do the two (enqueued) entities belong to the same group ? */ | |
326 | static inline struct cfs_rq * | |
327 | is_same_group(struct sched_entity *se, struct sched_entity *pse) | |
328 | { | |
329 | if (se->cfs_rq == pse->cfs_rq) | |
330 | return se->cfs_rq; | |
331 | ||
332 | return NULL; | |
333 | } | |
334 | ||
335 | static inline struct sched_entity *parent_entity(struct sched_entity *se) | |
336 | { | |
337 | return se->parent; | |
338 | } | |
339 | ||
340 | static void | |
341 | find_matching_se(struct sched_entity **se, struct sched_entity **pse) | |
342 | { | |
343 | int se_depth, pse_depth; | |
344 | ||
345 | /* | |
346 | * preemption test can be made between sibling entities who are in the | |
347 | * same cfs_rq i.e who have a common parent. Walk up the hierarchy of | |
348 | * both tasks until we find their ancestors who are siblings of common | |
349 | * parent. | |
350 | */ | |
351 | ||
352 | /* First walk up until both entities are at same depth */ | |
353 | se_depth = (*se)->depth; | |
354 | pse_depth = (*pse)->depth; | |
355 | ||
356 | while (se_depth > pse_depth) { | |
357 | se_depth--; | |
358 | *se = parent_entity(*se); | |
359 | } | |
360 | ||
361 | while (pse_depth > se_depth) { | |
362 | pse_depth--; | |
363 | *pse = parent_entity(*pse); | |
364 | } | |
365 | ||
366 | while (!is_same_group(*se, *pse)) { | |
367 | *se = parent_entity(*se); | |
368 | *pse = parent_entity(*pse); | |
369 | } | |
370 | } | |
371 | ||
372 | #else /* !CONFIG_FAIR_GROUP_SCHED */ | |
373 | ||
374 | static inline struct task_struct *task_of(struct sched_entity *se) | |
375 | { | |
376 | return container_of(se, struct task_struct, se); | |
377 | } | |
378 | ||
379 | static inline struct rq *rq_of(struct cfs_rq *cfs_rq) | |
380 | { | |
381 | return container_of(cfs_rq, struct rq, cfs); | |
382 | } | |
383 | ||
384 | #define entity_is_task(se) 1 | |
385 | ||
386 | #define for_each_sched_entity(se) \ | |
387 | for (; se; se = NULL) | |
388 | ||
389 | static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) | |
390 | { | |
391 | return &task_rq(p)->cfs; | |
392 | } | |
393 | ||
394 | static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) | |
395 | { | |
396 | struct task_struct *p = task_of(se); | |
397 | struct rq *rq = task_rq(p); | |
398 | ||
399 | return &rq->cfs; | |
400 | } | |
401 | ||
402 | /* runqueue "owned" by this group */ | |
403 | static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) | |
404 | { | |
405 | return NULL; | |
406 | } | |
407 | ||
408 | static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) | |
409 | { | |
410 | } | |
411 | ||
412 | static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) | |
413 | { | |
414 | } | |
415 | ||
416 | #define for_each_leaf_cfs_rq(rq, cfs_rq) \ | |
417 | for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL) | |
418 | ||
419 | static inline struct sched_entity *parent_entity(struct sched_entity *se) | |
420 | { | |
421 | return NULL; | |
422 | } | |
423 | ||
424 | static inline void | |
425 | find_matching_se(struct sched_entity **se, struct sched_entity **pse) | |
426 | { | |
427 | } | |
428 | ||
429 | #endif /* CONFIG_FAIR_GROUP_SCHED */ | |
430 | ||
431 | static __always_inline | |
432 | void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec); | |
433 | ||
434 | /************************************************************** | |
435 | * Scheduling class tree data structure manipulation methods: | |
436 | */ | |
437 | ||
438 | static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime) | |
439 | { | |
440 | s64 delta = (s64)(vruntime - max_vruntime); | |
441 | if (delta > 0) | |
442 | max_vruntime = vruntime; | |
443 | ||
444 | return max_vruntime; | |
445 | } | |
446 | ||
447 | static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) | |
448 | { | |
449 | s64 delta = (s64)(vruntime - min_vruntime); | |
450 | if (delta < 0) | |
451 | min_vruntime = vruntime; | |
452 | ||
453 | return min_vruntime; | |
454 | } | |
455 | ||
456 | static inline int entity_before(struct sched_entity *a, | |
457 | struct sched_entity *b) | |
458 | { | |
459 | return (s64)(a->vruntime - b->vruntime) < 0; | |
460 | } | |
461 | ||
462 | static void update_min_vruntime(struct cfs_rq *cfs_rq) | |
463 | { | |
464 | u64 vruntime = cfs_rq->min_vruntime; | |
465 | ||
466 | if (cfs_rq->curr) | |
467 | vruntime = cfs_rq->curr->vruntime; | |
468 | ||
469 | if (cfs_rq->rb_leftmost) { | |
470 | struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost, | |
471 | struct sched_entity, | |
472 | run_node); | |
473 | ||
474 | if (!cfs_rq->curr) | |
475 | vruntime = se->vruntime; | |
476 | else | |
477 | vruntime = min_vruntime(vruntime, se->vruntime); | |
478 | } | |
479 | ||
480 | /* ensure we never gain time by being placed backwards. */ | |
481 | cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); | |
482 | #ifndef CONFIG_64BIT | |
483 | smp_wmb(); | |
484 | cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; | |
485 | #endif | |
486 | } | |
487 | ||
488 | /* | |
489 | * Enqueue an entity into the rb-tree: | |
490 | */ | |
491 | static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
492 | { | |
493 | struct rb_node **link = &cfs_rq->tasks_timeline.rb_node; | |
494 | struct rb_node *parent = NULL; | |
495 | struct sched_entity *entry; | |
496 | int leftmost = 1; | |
497 | ||
498 | /* | |
499 | * Find the right place in the rbtree: | |
500 | */ | |
501 | while (*link) { | |
502 | parent = *link; | |
503 | entry = rb_entry(parent, struct sched_entity, run_node); | |
504 | /* | |
505 | * We dont care about collisions. Nodes with | |
506 | * the same key stay together. | |
507 | */ | |
508 | if (entity_before(se, entry)) { | |
509 | link = &parent->rb_left; | |
510 | } else { | |
511 | link = &parent->rb_right; | |
512 | leftmost = 0; | |
513 | } | |
514 | } | |
515 | ||
516 | /* | |
517 | * Maintain a cache of leftmost tree entries (it is frequently | |
518 | * used): | |
519 | */ | |
520 | if (leftmost) | |
521 | cfs_rq->rb_leftmost = &se->run_node; | |
522 | ||
523 | rb_link_node(&se->run_node, parent, link); | |
524 | rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline); | |
525 | } | |
526 | ||
527 | static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
528 | { | |
529 | if (cfs_rq->rb_leftmost == &se->run_node) { | |
530 | struct rb_node *next_node; | |
531 | ||
532 | next_node = rb_next(&se->run_node); | |
533 | cfs_rq->rb_leftmost = next_node; | |
534 | } | |
535 | ||
536 | rb_erase(&se->run_node, &cfs_rq->tasks_timeline); | |
537 | } | |
538 | ||
539 | struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) | |
540 | { | |
541 | struct rb_node *left = cfs_rq->rb_leftmost; | |
542 | ||
543 | if (!left) | |
544 | return NULL; | |
545 | ||
546 | return rb_entry(left, struct sched_entity, run_node); | |
547 | } | |
548 | ||
549 | static struct sched_entity *__pick_next_entity(struct sched_entity *se) | |
550 | { | |
551 | struct rb_node *next = rb_next(&se->run_node); | |
552 | ||
553 | if (!next) | |
554 | return NULL; | |
555 | ||
556 | return rb_entry(next, struct sched_entity, run_node); | |
557 | } | |
558 | ||
559 | #ifdef CONFIG_SCHED_DEBUG | |
560 | struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) | |
561 | { | |
562 | struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); | |
563 | ||
564 | if (!last) | |
565 | return NULL; | |
566 | ||
567 | return rb_entry(last, struct sched_entity, run_node); | |
568 | } | |
569 | ||
570 | /************************************************************** | |
571 | * Scheduling class statistics methods: | |
572 | */ | |
573 | ||
574 | int sched_proc_update_handler(struct ctl_table *table, int write, | |
575 | void __user *buffer, size_t *lenp, | |
576 | loff_t *ppos) | |
577 | { | |
578 | int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); | |
579 | unsigned int factor = get_update_sysctl_factor(); | |
580 | ||
581 | if (ret || !write) | |
582 | return ret; | |
583 | ||
584 | sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, | |
585 | sysctl_sched_min_granularity); | |
586 | ||
587 | #define WRT_SYSCTL(name) \ | |
588 | (normalized_sysctl_##name = sysctl_##name / (factor)) | |
589 | WRT_SYSCTL(sched_min_granularity); | |
590 | WRT_SYSCTL(sched_latency); | |
591 | WRT_SYSCTL(sched_wakeup_granularity); | |
592 | #undef WRT_SYSCTL | |
593 | ||
594 | return 0; | |
595 | } | |
596 | #endif | |
597 | ||
598 | /* | |
599 | * delta /= w | |
600 | */ | |
601 | static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se) | |
602 | { | |
603 | if (unlikely(se->load.weight != NICE_0_LOAD)) | |
604 | delta = __calc_delta(delta, NICE_0_LOAD, &se->load); | |
605 | ||
606 | return delta; | |
607 | } | |
608 | ||
609 | /* | |
610 | * The idea is to set a period in which each task runs once. | |
611 | * | |
612 | * When there are too many tasks (sched_nr_latency) we have to stretch | |
613 | * this period because otherwise the slices get too small. | |
614 | * | |
615 | * p = (nr <= nl) ? l : l*nr/nl | |
616 | */ | |
617 | static u64 __sched_period(unsigned long nr_running) | |
618 | { | |
619 | u64 period = sysctl_sched_latency; | |
620 | unsigned long nr_latency = sched_nr_latency; | |
621 | ||
622 | if (unlikely(nr_running > nr_latency)) { | |
623 | period = sysctl_sched_min_granularity; | |
624 | period *= nr_running; | |
625 | } | |
626 | ||
627 | return period; | |
628 | } | |
629 | ||
630 | /* | |
631 | * We calculate the wall-time slice from the period by taking a part | |
632 | * proportional to the weight. | |
633 | * | |
634 | * s = p*P[w/rw] | |
635 | */ | |
636 | static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
637 | { | |
638 | u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); | |
639 | ||
640 | for_each_sched_entity(se) { | |
641 | struct load_weight *load; | |
642 | struct load_weight lw; | |
643 | ||
644 | cfs_rq = cfs_rq_of(se); | |
645 | load = &cfs_rq->load; | |
646 | ||
647 | if (unlikely(!se->on_rq)) { | |
648 | lw = cfs_rq->load; | |
649 | ||
650 | update_load_add(&lw, se->load.weight); | |
651 | load = &lw; | |
652 | } | |
653 | slice = __calc_delta(slice, se->load.weight, load); | |
654 | } | |
655 | return slice; | |
656 | } | |
657 | ||
658 | /* | |
659 | * We calculate the vruntime slice of a to-be-inserted task. | |
660 | * | |
661 | * vs = s/w | |
662 | */ | |
663 | static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
664 | { | |
665 | return calc_delta_fair(sched_slice(cfs_rq, se), se); | |
666 | } | |
667 | ||
668 | #ifdef CONFIG_SMP | |
669 | static int select_idle_sibling(struct task_struct *p, int cpu); | |
670 | static unsigned long task_h_load(struct task_struct *p); | |
671 | ||
672 | static inline void __update_task_entity_contrib(struct sched_entity *se); | |
673 | static inline void __update_task_entity_utilization(struct sched_entity *se); | |
674 | ||
675 | /* Give new task start runnable values to heavy its load in infant time */ | |
676 | void init_task_runnable_average(struct task_struct *p) | |
677 | { | |
678 | u32 slice; | |
679 | ||
680 | slice = sched_slice(task_cfs_rq(p), &p->se) >> 10; | |
681 | p->se.avg.runnable_avg_sum = p->se.avg.running_avg_sum = slice; | |
682 | p->se.avg.avg_period = slice; | |
683 | __update_task_entity_contrib(&p->se); | |
684 | __update_task_entity_utilization(&p->se); | |
685 | } | |
686 | #else | |
687 | void init_task_runnable_average(struct task_struct *p) | |
688 | { | |
689 | } | |
690 | #endif | |
691 | ||
692 | /* | |
693 | * Update the current task's runtime statistics. | |
694 | */ | |
695 | static void update_curr(struct cfs_rq *cfs_rq) | |
696 | { | |
697 | struct sched_entity *curr = cfs_rq->curr; | |
698 | u64 now = rq_clock_task(rq_of(cfs_rq)); | |
699 | u64 delta_exec; | |
700 | ||
701 | if (unlikely(!curr)) | |
702 | return; | |
703 | ||
704 | delta_exec = now - curr->exec_start; | |
705 | if (unlikely((s64)delta_exec <= 0)) | |
706 | return; | |
707 | ||
708 | curr->exec_start = now; | |
709 | ||
710 | schedstat_set(curr->statistics.exec_max, | |
711 | max(delta_exec, curr->statistics.exec_max)); | |
712 | ||
713 | curr->sum_exec_runtime += delta_exec; | |
714 | schedstat_add(cfs_rq, exec_clock, delta_exec); | |
715 | ||
716 | curr->vruntime += calc_delta_fair(delta_exec, curr); | |
717 | update_min_vruntime(cfs_rq); | |
718 | ||
719 | if (entity_is_task(curr)) { | |
720 | struct task_struct *curtask = task_of(curr); | |
721 | ||
722 | trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); | |
723 | cpuacct_charge(curtask, delta_exec); | |
724 | account_group_exec_runtime(curtask, delta_exec); | |
725 | } | |
726 | ||
727 | account_cfs_rq_runtime(cfs_rq, delta_exec); | |
728 | } | |
729 | ||
730 | static void update_curr_fair(struct rq *rq) | |
731 | { | |
732 | update_curr(cfs_rq_of(&rq->curr->se)); | |
733 | } | |
734 | ||
735 | static inline void | |
736 | update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
737 | { | |
738 | schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq))); | |
739 | } | |
740 | ||
741 | /* | |
742 | * Task is being enqueued - update stats: | |
743 | */ | |
744 | static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
745 | { | |
746 | /* | |
747 | * Are we enqueueing a waiting task? (for current tasks | |
748 | * a dequeue/enqueue event is a NOP) | |
749 | */ | |
750 | if (se != cfs_rq->curr) | |
751 | update_stats_wait_start(cfs_rq, se); | |
752 | } | |
753 | ||
754 | static void | |
755 | update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
756 | { | |
757 | schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max, | |
758 | rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start)); | |
759 | schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1); | |
760 | schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum + | |
761 | rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start); | |
762 | #ifdef CONFIG_SCHEDSTATS | |
763 | if (entity_is_task(se)) { | |
764 | trace_sched_stat_wait(task_of(se), | |
765 | rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start); | |
766 | } | |
767 | #endif | |
768 | schedstat_set(se->statistics.wait_start, 0); | |
769 | } | |
770 | ||
771 | static inline void | |
772 | update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
773 | { | |
774 | /* | |
775 | * Mark the end of the wait period if dequeueing a | |
776 | * waiting task: | |
777 | */ | |
778 | if (se != cfs_rq->curr) | |
779 | update_stats_wait_end(cfs_rq, se); | |
780 | } | |
781 | ||
782 | /* | |
783 | * We are picking a new current task - update its stats: | |
784 | */ | |
785 | static inline void | |
786 | update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
787 | { | |
788 | /* | |
789 | * We are starting a new run period: | |
790 | */ | |
791 | se->exec_start = rq_clock_task(rq_of(cfs_rq)); | |
792 | } | |
793 | ||
794 | /************************************************** | |
795 | * Scheduling class queueing methods: | |
796 | */ | |
797 | ||
798 | #ifdef CONFIG_NUMA_BALANCING | |
799 | /* | |
800 | * Approximate time to scan a full NUMA task in ms. The task scan period is | |
801 | * calculated based on the tasks virtual memory size and | |
802 | * numa_balancing_scan_size. | |
803 | */ | |
804 | unsigned int sysctl_numa_balancing_scan_period_min = 1000; | |
805 | unsigned int sysctl_numa_balancing_scan_period_max = 60000; | |
806 | ||
807 | /* Portion of address space to scan in MB */ | |
808 | unsigned int sysctl_numa_balancing_scan_size = 256; | |
809 | ||
810 | /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */ | |
811 | unsigned int sysctl_numa_balancing_scan_delay = 1000; | |
812 | ||
813 | static unsigned int task_nr_scan_windows(struct task_struct *p) | |
814 | { | |
815 | unsigned long rss = 0; | |
816 | unsigned long nr_scan_pages; | |
817 | ||
818 | /* | |
819 | * Calculations based on RSS as non-present and empty pages are skipped | |
820 | * by the PTE scanner and NUMA hinting faults should be trapped based | |
821 | * on resident pages | |
822 | */ | |
823 | nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT); | |
824 | rss = get_mm_rss(p->mm); | |
825 | if (!rss) | |
826 | rss = nr_scan_pages; | |
827 | ||
828 | rss = round_up(rss, nr_scan_pages); | |
829 | return rss / nr_scan_pages; | |
830 | } | |
831 | ||
832 | /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */ | |
833 | #define MAX_SCAN_WINDOW 2560 | |
834 | ||
835 | static unsigned int task_scan_min(struct task_struct *p) | |
836 | { | |
837 | unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size); | |
838 | unsigned int scan, floor; | |
839 | unsigned int windows = 1; | |
840 | ||
841 | if (scan_size < MAX_SCAN_WINDOW) | |
842 | windows = MAX_SCAN_WINDOW / scan_size; | |
843 | floor = 1000 / windows; | |
844 | ||
845 | scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p); | |
846 | return max_t(unsigned int, floor, scan); | |
847 | } | |
848 | ||
849 | static unsigned int task_scan_max(struct task_struct *p) | |
850 | { | |
851 | unsigned int smin = task_scan_min(p); | |
852 | unsigned int smax; | |
853 | ||
854 | /* Watch for min being lower than max due to floor calculations */ | |
855 | smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p); | |
856 | return max(smin, smax); | |
857 | } | |
858 | ||
859 | static void account_numa_enqueue(struct rq *rq, struct task_struct *p) | |
860 | { | |
861 | rq->nr_numa_running += (p->numa_preferred_nid != -1); | |
862 | rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p)); | |
863 | } | |
864 | ||
865 | static void account_numa_dequeue(struct rq *rq, struct task_struct *p) | |
866 | { | |
867 | rq->nr_numa_running -= (p->numa_preferred_nid != -1); | |
868 | rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p)); | |
869 | } | |
870 | ||
871 | struct numa_group { | |
872 | atomic_t refcount; | |
873 | ||
874 | spinlock_t lock; /* nr_tasks, tasks */ | |
875 | int nr_tasks; | |
876 | pid_t gid; | |
877 | ||
878 | struct rcu_head rcu; | |
879 | nodemask_t active_nodes; | |
880 | unsigned long total_faults; | |
881 | /* | |
882 | * Faults_cpu is used to decide whether memory should move | |
883 | * towards the CPU. As a consequence, these stats are weighted | |
884 | * more by CPU use than by memory faults. | |
885 | */ | |
886 | unsigned long *faults_cpu; | |
887 | unsigned long faults[0]; | |
888 | }; | |
889 | ||
890 | /* Shared or private faults. */ | |
891 | #define NR_NUMA_HINT_FAULT_TYPES 2 | |
892 | ||
893 | /* Memory and CPU locality */ | |
894 | #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2) | |
895 | ||
896 | /* Averaged statistics, and temporary buffers. */ | |
897 | #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2) | |
898 | ||
899 | pid_t task_numa_group_id(struct task_struct *p) | |
900 | { | |
901 | return p->numa_group ? p->numa_group->gid : 0; | |
902 | } | |
903 | ||
904 | /* | |
905 | * The averaged statistics, shared & private, memory & cpu, | |
906 | * occupy the first half of the array. The second half of the | |
907 | * array is for current counters, which are averaged into the | |
908 | * first set by task_numa_placement. | |
909 | */ | |
910 | static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv) | |
911 | { | |
912 | return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv; | |
913 | } | |
914 | ||
915 | static inline unsigned long task_faults(struct task_struct *p, int nid) | |
916 | { | |
917 | if (!p->numa_faults) | |
918 | return 0; | |
919 | ||
920 | return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] + | |
921 | p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)]; | |
922 | } | |
923 | ||
924 | static inline unsigned long group_faults(struct task_struct *p, int nid) | |
925 | { | |
926 | if (!p->numa_group) | |
927 | return 0; | |
928 | ||
929 | return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] + | |
930 | p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)]; | |
931 | } | |
932 | ||
933 | static inline unsigned long group_faults_cpu(struct numa_group *group, int nid) | |
934 | { | |
935 | return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] + | |
936 | group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)]; | |
937 | } | |
938 | ||
939 | /* Handle placement on systems where not all nodes are directly connected. */ | |
940 | static unsigned long score_nearby_nodes(struct task_struct *p, int nid, | |
941 | int maxdist, bool task) | |
942 | { | |
943 | unsigned long score = 0; | |
944 | int node; | |
945 | ||
946 | /* | |
947 | * All nodes are directly connected, and the same distance | |
948 | * from each other. No need for fancy placement algorithms. | |
949 | */ | |
950 | if (sched_numa_topology_type == NUMA_DIRECT) | |
951 | return 0; | |
952 | ||
953 | /* | |
954 | * This code is called for each node, introducing N^2 complexity, | |
955 | * which should be ok given the number of nodes rarely exceeds 8. | |
956 | */ | |
957 | for_each_online_node(node) { | |
958 | unsigned long faults; | |
959 | int dist = node_distance(nid, node); | |
960 | ||
961 | /* | |
962 | * The furthest away nodes in the system are not interesting | |
963 | * for placement; nid was already counted. | |
964 | */ | |
965 | if (dist == sched_max_numa_distance || node == nid) | |
966 | continue; | |
967 | ||
968 | /* | |
969 | * On systems with a backplane NUMA topology, compare groups | |
970 | * of nodes, and move tasks towards the group with the most | |
971 | * memory accesses. When comparing two nodes at distance | |
972 | * "hoplimit", only nodes closer by than "hoplimit" are part | |
973 | * of each group. Skip other nodes. | |
974 | */ | |
975 | if (sched_numa_topology_type == NUMA_BACKPLANE && | |
976 | dist > maxdist) | |
977 | continue; | |
978 | ||
979 | /* Add up the faults from nearby nodes. */ | |
980 | if (task) | |
981 | faults = task_faults(p, node); | |
982 | else | |
983 | faults = group_faults(p, node); | |
984 | ||
985 | /* | |
986 | * On systems with a glueless mesh NUMA topology, there are | |
987 | * no fixed "groups of nodes". Instead, nodes that are not | |
988 | * directly connected bounce traffic through intermediate | |
989 | * nodes; a numa_group can occupy any set of nodes. | |
990 | * The further away a node is, the less the faults count. | |
991 | * This seems to result in good task placement. | |
992 | */ | |
993 | if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { | |
994 | faults *= (sched_max_numa_distance - dist); | |
995 | faults /= (sched_max_numa_distance - LOCAL_DISTANCE); | |
996 | } | |
997 | ||
998 | score += faults; | |
999 | } | |
1000 | ||
1001 | return score; | |
1002 | } | |
1003 | ||
1004 | /* | |
1005 | * These return the fraction of accesses done by a particular task, or | |
1006 | * task group, on a particular numa node. The group weight is given a | |
1007 | * larger multiplier, in order to group tasks together that are almost | |
1008 | * evenly spread out between numa nodes. | |
1009 | */ | |
1010 | static inline unsigned long task_weight(struct task_struct *p, int nid, | |
1011 | int dist) | |
1012 | { | |
1013 | unsigned long faults, total_faults; | |
1014 | ||
1015 | if (!p->numa_faults) | |
1016 | return 0; | |
1017 | ||
1018 | total_faults = p->total_numa_faults; | |
1019 | ||
1020 | if (!total_faults) | |
1021 | return 0; | |
1022 | ||
1023 | faults = task_faults(p, nid); | |
1024 | faults += score_nearby_nodes(p, nid, dist, true); | |
1025 | ||
1026 | return 1000 * faults / total_faults; | |
1027 | } | |
1028 | ||
1029 | static inline unsigned long group_weight(struct task_struct *p, int nid, | |
1030 | int dist) | |
1031 | { | |
1032 | unsigned long faults, total_faults; | |
1033 | ||
1034 | if (!p->numa_group) | |
1035 | return 0; | |
1036 | ||
1037 | total_faults = p->numa_group->total_faults; | |
1038 | ||
1039 | if (!total_faults) | |
1040 | return 0; | |
1041 | ||
1042 | faults = group_faults(p, nid); | |
1043 | faults += score_nearby_nodes(p, nid, dist, false); | |
1044 | ||
1045 | return 1000 * faults / total_faults; | |
1046 | } | |
1047 | ||
1048 | bool should_numa_migrate_memory(struct task_struct *p, struct page * page, | |
1049 | int src_nid, int dst_cpu) | |
1050 | { | |
1051 | struct numa_group *ng = p->numa_group; | |
1052 | int dst_nid = cpu_to_node(dst_cpu); | |
1053 | int last_cpupid, this_cpupid; | |
1054 | ||
1055 | this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); | |
1056 | ||
1057 | /* | |
1058 | * Multi-stage node selection is used in conjunction with a periodic | |
1059 | * migration fault to build a temporal task<->page relation. By using | |
1060 | * a two-stage filter we remove short/unlikely relations. | |
1061 | * | |
1062 | * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate | |
1063 | * a task's usage of a particular page (n_p) per total usage of this | |
1064 | * page (n_t) (in a given time-span) to a probability. | |
1065 | * | |
1066 | * Our periodic faults will sample this probability and getting the | |
1067 | * same result twice in a row, given these samples are fully | |
1068 | * independent, is then given by P(n)^2, provided our sample period | |
1069 | * is sufficiently short compared to the usage pattern. | |
1070 | * | |
1071 | * This quadric squishes small probabilities, making it less likely we | |
1072 | * act on an unlikely task<->page relation. | |
1073 | */ | |
1074 | last_cpupid = page_cpupid_xchg_last(page, this_cpupid); | |
1075 | if (!cpupid_pid_unset(last_cpupid) && | |
1076 | cpupid_to_nid(last_cpupid) != dst_nid) | |
1077 | return false; | |
1078 | ||
1079 | /* Always allow migrate on private faults */ | |
1080 | if (cpupid_match_pid(p, last_cpupid)) | |
1081 | return true; | |
1082 | ||
1083 | /* A shared fault, but p->numa_group has not been set up yet. */ | |
1084 | if (!ng) | |
1085 | return true; | |
1086 | ||
1087 | /* | |
1088 | * Do not migrate if the destination is not a node that | |
1089 | * is actively used by this numa group. | |
1090 | */ | |
1091 | if (!node_isset(dst_nid, ng->active_nodes)) | |
1092 | return false; | |
1093 | ||
1094 | /* | |
1095 | * Source is a node that is not actively used by this | |
1096 | * numa group, while the destination is. Migrate. | |
1097 | */ | |
1098 | if (!node_isset(src_nid, ng->active_nodes)) | |
1099 | return true; | |
1100 | ||
1101 | /* | |
1102 | * Both source and destination are nodes in active | |
1103 | * use by this numa group. Maximize memory bandwidth | |
1104 | * by migrating from more heavily used groups, to less | |
1105 | * heavily used ones, spreading the load around. | |
1106 | * Use a 1/4 hysteresis to avoid spurious page movement. | |
1107 | */ | |
1108 | return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4); | |
1109 | } | |
1110 | ||
1111 | static unsigned long weighted_cpuload(const int cpu); | |
1112 | static unsigned long source_load(int cpu, int type); | |
1113 | static unsigned long target_load(int cpu, int type); | |
1114 | static unsigned long capacity_of(int cpu); | |
1115 | static long effective_load(struct task_group *tg, int cpu, long wl, long wg); | |
1116 | ||
1117 | /* Cached statistics for all CPUs within a node */ | |
1118 | struct numa_stats { | |
1119 | unsigned long nr_running; | |
1120 | unsigned long load; | |
1121 | ||
1122 | /* Total compute capacity of CPUs on a node */ | |
1123 | unsigned long compute_capacity; | |
1124 | ||
1125 | /* Approximate capacity in terms of runnable tasks on a node */ | |
1126 | unsigned long task_capacity; | |
1127 | int has_free_capacity; | |
1128 | }; | |
1129 | ||
1130 | /* | |
1131 | * XXX borrowed from update_sg_lb_stats | |
1132 | */ | |
1133 | static void update_numa_stats(struct numa_stats *ns, int nid) | |
1134 | { | |
1135 | int smt, cpu, cpus = 0; | |
1136 | unsigned long capacity; | |
1137 | ||
1138 | memset(ns, 0, sizeof(*ns)); | |
1139 | for_each_cpu(cpu, cpumask_of_node(nid)) { | |
1140 | struct rq *rq = cpu_rq(cpu); | |
1141 | ||
1142 | ns->nr_running += rq->nr_running; | |
1143 | ns->load += weighted_cpuload(cpu); | |
1144 | ns->compute_capacity += capacity_of(cpu); | |
1145 | ||
1146 | cpus++; | |
1147 | } | |
1148 | ||
1149 | /* | |
1150 | * If we raced with hotplug and there are no CPUs left in our mask | |
1151 | * the @ns structure is NULL'ed and task_numa_compare() will | |
1152 | * not find this node attractive. | |
1153 | * | |
1154 | * We'll either bail at !has_free_capacity, or we'll detect a huge | |
1155 | * imbalance and bail there. | |
1156 | */ | |
1157 | if (!cpus) | |
1158 | return; | |
1159 | ||
1160 | /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */ | |
1161 | smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity); | |
1162 | capacity = cpus / smt; /* cores */ | |
1163 | ||
1164 | ns->task_capacity = min_t(unsigned, capacity, | |
1165 | DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE)); | |
1166 | ns->has_free_capacity = (ns->nr_running < ns->task_capacity); | |
1167 | } | |
1168 | ||
1169 | struct task_numa_env { | |
1170 | struct task_struct *p; | |
1171 | ||
1172 | int src_cpu, src_nid; | |
1173 | int dst_cpu, dst_nid; | |
1174 | ||
1175 | struct numa_stats src_stats, dst_stats; | |
1176 | ||
1177 | int imbalance_pct; | |
1178 | int dist; | |
1179 | ||
1180 | struct task_struct *best_task; | |
1181 | long best_imp; | |
1182 | int best_cpu; | |
1183 | }; | |
1184 | ||
1185 | static void task_numa_assign(struct task_numa_env *env, | |
1186 | struct task_struct *p, long imp) | |
1187 | { | |
1188 | if (env->best_task) | |
1189 | put_task_struct(env->best_task); | |
1190 | if (p) | |
1191 | get_task_struct(p); | |
1192 | ||
1193 | env->best_task = p; | |
1194 | env->best_imp = imp; | |
1195 | env->best_cpu = env->dst_cpu; | |
1196 | } | |
1197 | ||
1198 | static bool load_too_imbalanced(long src_load, long dst_load, | |
1199 | struct task_numa_env *env) | |
1200 | { | |
1201 | long imb, old_imb; | |
1202 | long orig_src_load, orig_dst_load; | |
1203 | long src_capacity, dst_capacity; | |
1204 | ||
1205 | /* | |
1206 | * The load is corrected for the CPU capacity available on each node. | |
1207 | * | |
1208 | * src_load dst_load | |
1209 | * ------------ vs --------- | |
1210 | * src_capacity dst_capacity | |
1211 | */ | |
1212 | src_capacity = env->src_stats.compute_capacity; | |
1213 | dst_capacity = env->dst_stats.compute_capacity; | |
1214 | ||
1215 | /* We care about the slope of the imbalance, not the direction. */ | |
1216 | if (dst_load < src_load) | |
1217 | swap(dst_load, src_load); | |
1218 | ||
1219 | /* Is the difference below the threshold? */ | |
1220 | imb = dst_load * src_capacity * 100 - | |
1221 | src_load * dst_capacity * env->imbalance_pct; | |
1222 | if (imb <= 0) | |
1223 | return false; | |
1224 | ||
1225 | /* | |
1226 | * The imbalance is above the allowed threshold. | |
1227 | * Compare it with the old imbalance. | |
1228 | */ | |
1229 | orig_src_load = env->src_stats.load; | |
1230 | orig_dst_load = env->dst_stats.load; | |
1231 | ||
1232 | if (orig_dst_load < orig_src_load) | |
1233 | swap(orig_dst_load, orig_src_load); | |
1234 | ||
1235 | old_imb = orig_dst_load * src_capacity * 100 - | |
1236 | orig_src_load * dst_capacity * env->imbalance_pct; | |
1237 | ||
1238 | /* Would this change make things worse? */ | |
1239 | return (imb > old_imb); | |
1240 | } | |
1241 | ||
1242 | /* | |
1243 | * This checks if the overall compute and NUMA accesses of the system would | |
1244 | * be improved if the source tasks was migrated to the target dst_cpu taking | |
1245 | * into account that it might be best if task running on the dst_cpu should | |
1246 | * be exchanged with the source task | |
1247 | */ | |
1248 | static void task_numa_compare(struct task_numa_env *env, | |
1249 | long taskimp, long groupimp) | |
1250 | { | |
1251 | struct rq *src_rq = cpu_rq(env->src_cpu); | |
1252 | struct rq *dst_rq = cpu_rq(env->dst_cpu); | |
1253 | struct task_struct *cur; | |
1254 | long src_load, dst_load; | |
1255 | long load; | |
1256 | long imp = env->p->numa_group ? groupimp : taskimp; | |
1257 | long moveimp = imp; | |
1258 | int dist = env->dist; | |
1259 | ||
1260 | rcu_read_lock(); | |
1261 | ||
1262 | raw_spin_lock_irq(&dst_rq->lock); | |
1263 | cur = dst_rq->curr; | |
1264 | /* | |
1265 | * No need to move the exiting task, and this ensures that ->curr | |
1266 | * wasn't reaped and thus get_task_struct() in task_numa_assign() | |
1267 | * is safe under RCU read lock. | |
1268 | * Note that rcu_read_lock() itself can't protect from the final | |
1269 | * put_task_struct() after the last schedule(). | |
1270 | */ | |
1271 | if ((cur->flags & PF_EXITING) || is_idle_task(cur)) | |
1272 | cur = NULL; | |
1273 | raw_spin_unlock_irq(&dst_rq->lock); | |
1274 | ||
1275 | /* | |
1276 | * Because we have preemption enabled we can get migrated around and | |
1277 | * end try selecting ourselves (current == env->p) as a swap candidate. | |
1278 | */ | |
1279 | if (cur == env->p) | |
1280 | goto unlock; | |
1281 | ||
1282 | /* | |
1283 | * "imp" is the fault differential for the source task between the | |
1284 | * source and destination node. Calculate the total differential for | |
1285 | * the source task and potential destination task. The more negative | |
1286 | * the value is, the more rmeote accesses that would be expected to | |
1287 | * be incurred if the tasks were swapped. | |
1288 | */ | |
1289 | if (cur) { | |
1290 | /* Skip this swap candidate if cannot move to the source cpu */ | |
1291 | if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur))) | |
1292 | goto unlock; | |
1293 | ||
1294 | /* | |
1295 | * If dst and source tasks are in the same NUMA group, or not | |
1296 | * in any group then look only at task weights. | |
1297 | */ | |
1298 | if (cur->numa_group == env->p->numa_group) { | |
1299 | imp = taskimp + task_weight(cur, env->src_nid, dist) - | |
1300 | task_weight(cur, env->dst_nid, dist); | |
1301 | /* | |
1302 | * Add some hysteresis to prevent swapping the | |
1303 | * tasks within a group over tiny differences. | |
1304 | */ | |
1305 | if (cur->numa_group) | |
1306 | imp -= imp/16; | |
1307 | } else { | |
1308 | /* | |
1309 | * Compare the group weights. If a task is all by | |
1310 | * itself (not part of a group), use the task weight | |
1311 | * instead. | |
1312 | */ | |
1313 | if (cur->numa_group) | |
1314 | imp += group_weight(cur, env->src_nid, dist) - | |
1315 | group_weight(cur, env->dst_nid, dist); | |
1316 | else | |
1317 | imp += task_weight(cur, env->src_nid, dist) - | |
1318 | task_weight(cur, env->dst_nid, dist); | |
1319 | } | |
1320 | } | |
1321 | ||
1322 | if (imp <= env->best_imp && moveimp <= env->best_imp) | |
1323 | goto unlock; | |
1324 | ||
1325 | if (!cur) { | |
1326 | /* Is there capacity at our destination? */ | |
1327 | if (env->src_stats.nr_running <= env->src_stats.task_capacity && | |
1328 | !env->dst_stats.has_free_capacity) | |
1329 | goto unlock; | |
1330 | ||
1331 | goto balance; | |
1332 | } | |
1333 | ||
1334 | /* Balance doesn't matter much if we're running a task per cpu */ | |
1335 | if (imp > env->best_imp && src_rq->nr_running == 1 && | |
1336 | dst_rq->nr_running == 1) | |
1337 | goto assign; | |
1338 | ||
1339 | /* | |
1340 | * In the overloaded case, try and keep the load balanced. | |
1341 | */ | |
1342 | balance: | |
1343 | load = task_h_load(env->p); | |
1344 | dst_load = env->dst_stats.load + load; | |
1345 | src_load = env->src_stats.load - load; | |
1346 | ||
1347 | if (moveimp > imp && moveimp > env->best_imp) { | |
1348 | /* | |
1349 | * If the improvement from just moving env->p direction is | |
1350 | * better than swapping tasks around, check if a move is | |
1351 | * possible. Store a slightly smaller score than moveimp, | |
1352 | * so an actually idle CPU will win. | |
1353 | */ | |
1354 | if (!load_too_imbalanced(src_load, dst_load, env)) { | |
1355 | imp = moveimp - 1; | |
1356 | cur = NULL; | |
1357 | goto assign; | |
1358 | } | |
1359 | } | |
1360 | ||
1361 | if (imp <= env->best_imp) | |
1362 | goto unlock; | |
1363 | ||
1364 | if (cur) { | |
1365 | load = task_h_load(cur); | |
1366 | dst_load -= load; | |
1367 | src_load += load; | |
1368 | } | |
1369 | ||
1370 | if (load_too_imbalanced(src_load, dst_load, env)) | |
1371 | goto unlock; | |
1372 | ||
1373 | /* | |
1374 | * One idle CPU per node is evaluated for a task numa move. | |
1375 | * Call select_idle_sibling to maybe find a better one. | |
1376 | */ | |
1377 | if (!cur) | |
1378 | env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu); | |
1379 | ||
1380 | assign: | |
1381 | task_numa_assign(env, cur, imp); | |
1382 | unlock: | |
1383 | rcu_read_unlock(); | |
1384 | } | |
1385 | ||
1386 | static void task_numa_find_cpu(struct task_numa_env *env, | |
1387 | long taskimp, long groupimp) | |
1388 | { | |
1389 | int cpu; | |
1390 | ||
1391 | for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) { | |
1392 | /* Skip this CPU if the source task cannot migrate */ | |
1393 | if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p))) | |
1394 | continue; | |
1395 | ||
1396 | env->dst_cpu = cpu; | |
1397 | task_numa_compare(env, taskimp, groupimp); | |
1398 | } | |
1399 | } | |
1400 | ||
1401 | /* Only move tasks to a NUMA node less busy than the current node. */ | |
1402 | static bool numa_has_capacity(struct task_numa_env *env) | |
1403 | { | |
1404 | struct numa_stats *src = &env->src_stats; | |
1405 | struct numa_stats *dst = &env->dst_stats; | |
1406 | ||
1407 | if (src->has_free_capacity && !dst->has_free_capacity) | |
1408 | return false; | |
1409 | ||
1410 | /* | |
1411 | * Only consider a task move if the source has a higher load | |
1412 | * than the destination, corrected for CPU capacity on each node. | |
1413 | * | |
1414 | * src->load dst->load | |
1415 | * --------------------- vs --------------------- | |
1416 | * src->compute_capacity dst->compute_capacity | |
1417 | */ | |
1418 | if (src->load * dst->compute_capacity > | |
1419 | dst->load * src->compute_capacity) | |
1420 | return true; | |
1421 | ||
1422 | return false; | |
1423 | } | |
1424 | ||
1425 | static int task_numa_migrate(struct task_struct *p) | |
1426 | { | |
1427 | struct task_numa_env env = { | |
1428 | .p = p, | |
1429 | ||
1430 | .src_cpu = task_cpu(p), | |
1431 | .src_nid = task_node(p), | |
1432 | ||
1433 | .imbalance_pct = 112, | |
1434 | ||
1435 | .best_task = NULL, | |
1436 | .best_imp = 0, | |
1437 | .best_cpu = -1 | |
1438 | }; | |
1439 | struct sched_domain *sd; | |
1440 | unsigned long taskweight, groupweight; | |
1441 | int nid, ret, dist; | |
1442 | long taskimp, groupimp; | |
1443 | ||
1444 | /* | |
1445 | * Pick the lowest SD_NUMA domain, as that would have the smallest | |
1446 | * imbalance and would be the first to start moving tasks about. | |
1447 | * | |
1448 | * And we want to avoid any moving of tasks about, as that would create | |
1449 | * random movement of tasks -- counter the numa conditions we're trying | |
1450 | * to satisfy here. | |
1451 | */ | |
1452 | rcu_read_lock(); | |
1453 | sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); | |
1454 | if (sd) | |
1455 | env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; | |
1456 | rcu_read_unlock(); | |
1457 | ||
1458 | /* | |
1459 | * Cpusets can break the scheduler domain tree into smaller | |
1460 | * balance domains, some of which do not cross NUMA boundaries. | |
1461 | * Tasks that are "trapped" in such domains cannot be migrated | |
1462 | * elsewhere, so there is no point in (re)trying. | |
1463 | */ | |
1464 | if (unlikely(!sd)) { | |
1465 | p->numa_preferred_nid = task_node(p); | |
1466 | return -EINVAL; | |
1467 | } | |
1468 | ||
1469 | env.dst_nid = p->numa_preferred_nid; | |
1470 | dist = env.dist = node_distance(env.src_nid, env.dst_nid); | |
1471 | taskweight = task_weight(p, env.src_nid, dist); | |
1472 | groupweight = group_weight(p, env.src_nid, dist); | |
1473 | update_numa_stats(&env.src_stats, env.src_nid); | |
1474 | taskimp = task_weight(p, env.dst_nid, dist) - taskweight; | |
1475 | groupimp = group_weight(p, env.dst_nid, dist) - groupweight; | |
1476 | update_numa_stats(&env.dst_stats, env.dst_nid); | |
1477 | ||
1478 | /* Try to find a spot on the preferred nid. */ | |
1479 | if (numa_has_capacity(&env)) | |
1480 | task_numa_find_cpu(&env, taskimp, groupimp); | |
1481 | ||
1482 | /* | |
1483 | * Look at other nodes in these cases: | |
1484 | * - there is no space available on the preferred_nid | |
1485 | * - the task is part of a numa_group that is interleaved across | |
1486 | * multiple NUMA nodes; in order to better consolidate the group, | |
1487 | * we need to check other locations. | |
1488 | */ | |
1489 | if (env.best_cpu == -1 || (p->numa_group && | |
1490 | nodes_weight(p->numa_group->active_nodes) > 1)) { | |
1491 | for_each_online_node(nid) { | |
1492 | if (nid == env.src_nid || nid == p->numa_preferred_nid) | |
1493 | continue; | |
1494 | ||
1495 | dist = node_distance(env.src_nid, env.dst_nid); | |
1496 | if (sched_numa_topology_type == NUMA_BACKPLANE && | |
1497 | dist != env.dist) { | |
1498 | taskweight = task_weight(p, env.src_nid, dist); | |
1499 | groupweight = group_weight(p, env.src_nid, dist); | |
1500 | } | |
1501 | ||
1502 | /* Only consider nodes where both task and groups benefit */ | |
1503 | taskimp = task_weight(p, nid, dist) - taskweight; | |
1504 | groupimp = group_weight(p, nid, dist) - groupweight; | |
1505 | if (taskimp < 0 && groupimp < 0) | |
1506 | continue; | |
1507 | ||
1508 | env.dist = dist; | |
1509 | env.dst_nid = nid; | |
1510 | update_numa_stats(&env.dst_stats, env.dst_nid); | |
1511 | if (numa_has_capacity(&env)) | |
1512 | task_numa_find_cpu(&env, taskimp, groupimp); | |
1513 | } | |
1514 | } | |
1515 | ||
1516 | /* | |
1517 | * If the task is part of a workload that spans multiple NUMA nodes, | |
1518 | * and is migrating into one of the workload's active nodes, remember | |
1519 | * this node as the task's preferred numa node, so the workload can | |
1520 | * settle down. | |
1521 | * A task that migrated to a second choice node will be better off | |
1522 | * trying for a better one later. Do not set the preferred node here. | |
1523 | */ | |
1524 | if (p->numa_group) { | |
1525 | if (env.best_cpu == -1) | |
1526 | nid = env.src_nid; | |
1527 | else | |
1528 | nid = env.dst_nid; | |
1529 | ||
1530 | if (node_isset(nid, p->numa_group->active_nodes)) | |
1531 | sched_setnuma(p, env.dst_nid); | |
1532 | } | |
1533 | ||
1534 | /* No better CPU than the current one was found. */ | |
1535 | if (env.best_cpu == -1) | |
1536 | return -EAGAIN; | |
1537 | ||
1538 | /* | |
1539 | * Reset the scan period if the task is being rescheduled on an | |
1540 | * alternative node to recheck if the tasks is now properly placed. | |
1541 | */ | |
1542 | p->numa_scan_period = task_scan_min(p); | |
1543 | ||
1544 | if (env.best_task == NULL) { | |
1545 | ret = migrate_task_to(p, env.best_cpu); | |
1546 | if (ret != 0) | |
1547 | trace_sched_stick_numa(p, env.src_cpu, env.best_cpu); | |
1548 | return ret; | |
1549 | } | |
1550 | ||
1551 | ret = migrate_swap(p, env.best_task); | |
1552 | if (ret != 0) | |
1553 | trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task)); | |
1554 | put_task_struct(env.best_task); | |
1555 | return ret; | |
1556 | } | |
1557 | ||
1558 | /* Attempt to migrate a task to a CPU on the preferred node. */ | |
1559 | static void numa_migrate_preferred(struct task_struct *p) | |
1560 | { | |
1561 | unsigned long interval = HZ; | |
1562 | ||
1563 | /* This task has no NUMA fault statistics yet */ | |
1564 | if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults)) | |
1565 | return; | |
1566 | ||
1567 | /* Periodically retry migrating the task to the preferred node */ | |
1568 | interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16); | |
1569 | p->numa_migrate_retry = jiffies + interval; | |
1570 | ||
1571 | /* Success if task is already running on preferred CPU */ | |
1572 | if (task_node(p) == p->numa_preferred_nid) | |
1573 | return; | |
1574 | ||
1575 | /* Otherwise, try migrate to a CPU on the preferred node */ | |
1576 | task_numa_migrate(p); | |
1577 | } | |
1578 | ||
1579 | /* | |
1580 | * Find the nodes on which the workload is actively running. We do this by | |
1581 | * tracking the nodes from which NUMA hinting faults are triggered. This can | |
1582 | * be different from the set of nodes where the workload's memory is currently | |
1583 | * located. | |
1584 | * | |
1585 | * The bitmask is used to make smarter decisions on when to do NUMA page | |
1586 | * migrations, To prevent flip-flopping, and excessive page migrations, nodes | |
1587 | * are added when they cause over 6/16 of the maximum number of faults, but | |
1588 | * only removed when they drop below 3/16. | |
1589 | */ | |
1590 | static void update_numa_active_node_mask(struct numa_group *numa_group) | |
1591 | { | |
1592 | unsigned long faults, max_faults = 0; | |
1593 | int nid; | |
1594 | ||
1595 | for_each_online_node(nid) { | |
1596 | faults = group_faults_cpu(numa_group, nid); | |
1597 | if (faults > max_faults) | |
1598 | max_faults = faults; | |
1599 | } | |
1600 | ||
1601 | for_each_online_node(nid) { | |
1602 | faults = group_faults_cpu(numa_group, nid); | |
1603 | if (!node_isset(nid, numa_group->active_nodes)) { | |
1604 | if (faults > max_faults * 6 / 16) | |
1605 | node_set(nid, numa_group->active_nodes); | |
1606 | } else if (faults < max_faults * 3 / 16) | |
1607 | node_clear(nid, numa_group->active_nodes); | |
1608 | } | |
1609 | } | |
1610 | ||
1611 | /* | |
1612 | * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS | |
1613 | * increments. The more local the fault statistics are, the higher the scan | |
1614 | * period will be for the next scan window. If local/(local+remote) ratio is | |
1615 | * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) | |
1616 | * the scan period will decrease. Aim for 70% local accesses. | |
1617 | */ | |
1618 | #define NUMA_PERIOD_SLOTS 10 | |
1619 | #define NUMA_PERIOD_THRESHOLD 7 | |
1620 | ||
1621 | /* | |
1622 | * Increase the scan period (slow down scanning) if the majority of | |
1623 | * our memory is already on our local node, or if the majority of | |
1624 | * the page accesses are shared with other processes. | |
1625 | * Otherwise, decrease the scan period. | |
1626 | */ | |
1627 | static void update_task_scan_period(struct task_struct *p, | |
1628 | unsigned long shared, unsigned long private) | |
1629 | { | |
1630 | unsigned int period_slot; | |
1631 | int ratio; | |
1632 | int diff; | |
1633 | ||
1634 | unsigned long remote = p->numa_faults_locality[0]; | |
1635 | unsigned long local = p->numa_faults_locality[1]; | |
1636 | ||
1637 | /* | |
1638 | * If there were no record hinting faults then either the task is | |
1639 | * completely idle or all activity is areas that are not of interest | |
1640 | * to automatic numa balancing. Related to that, if there were failed | |
1641 | * migration then it implies we are migrating too quickly or the local | |
1642 | * node is overloaded. In either case, scan slower | |
1643 | */ | |
1644 | if (local + shared == 0 || p->numa_faults_locality[2]) { | |
1645 | p->numa_scan_period = min(p->numa_scan_period_max, | |
1646 | p->numa_scan_period << 1); | |
1647 | ||
1648 | p->mm->numa_next_scan = jiffies + | |
1649 | msecs_to_jiffies(p->numa_scan_period); | |
1650 | ||
1651 | return; | |
1652 | } | |
1653 | ||
1654 | /* | |
1655 | * Prepare to scale scan period relative to the current period. | |
1656 | * == NUMA_PERIOD_THRESHOLD scan period stays the same | |
1657 | * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster) | |
1658 | * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower) | |
1659 | */ | |
1660 | period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS); | |
1661 | ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote); | |
1662 | if (ratio >= NUMA_PERIOD_THRESHOLD) { | |
1663 | int slot = ratio - NUMA_PERIOD_THRESHOLD; | |
1664 | if (!slot) | |
1665 | slot = 1; | |
1666 | diff = slot * period_slot; | |
1667 | } else { | |
1668 | diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot; | |
1669 | ||
1670 | /* | |
1671 | * Scale scan rate increases based on sharing. There is an | |
1672 | * inverse relationship between the degree of sharing and | |
1673 | * the adjustment made to the scanning period. Broadly | |
1674 | * speaking the intent is that there is little point | |
1675 | * scanning faster if shared accesses dominate as it may | |
1676 | * simply bounce migrations uselessly | |
1677 | */ | |
1678 | ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1)); | |
1679 | diff = (diff * ratio) / NUMA_PERIOD_SLOTS; | |
1680 | } | |
1681 | ||
1682 | p->numa_scan_period = clamp(p->numa_scan_period + diff, | |
1683 | task_scan_min(p), task_scan_max(p)); | |
1684 | memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); | |
1685 | } | |
1686 | ||
1687 | /* | |
1688 | * Get the fraction of time the task has been running since the last | |
1689 | * NUMA placement cycle. The scheduler keeps similar statistics, but | |
1690 | * decays those on a 32ms period, which is orders of magnitude off | |
1691 | * from the dozens-of-seconds NUMA balancing period. Use the scheduler | |
1692 | * stats only if the task is so new there are no NUMA statistics yet. | |
1693 | */ | |
1694 | static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period) | |
1695 | { | |
1696 | u64 runtime, delta, now; | |
1697 | /* Use the start of this time slice to avoid calculations. */ | |
1698 | now = p->se.exec_start; | |
1699 | runtime = p->se.sum_exec_runtime; | |
1700 | ||
1701 | if (p->last_task_numa_placement) { | |
1702 | delta = runtime - p->last_sum_exec_runtime; | |
1703 | *period = now - p->last_task_numa_placement; | |
1704 | } else { | |
1705 | delta = p->se.avg.runnable_avg_sum; | |
1706 | *period = p->se.avg.avg_period; | |
1707 | } | |
1708 | ||
1709 | p->last_sum_exec_runtime = runtime; | |
1710 | p->last_task_numa_placement = now; | |
1711 | ||
1712 | return delta; | |
1713 | } | |
1714 | ||
1715 | /* | |
1716 | * Determine the preferred nid for a task in a numa_group. This needs to | |
1717 | * be done in a way that produces consistent results with group_weight, | |
1718 | * otherwise workloads might not converge. | |
1719 | */ | |
1720 | static int preferred_group_nid(struct task_struct *p, int nid) | |
1721 | { | |
1722 | nodemask_t nodes; | |
1723 | int dist; | |
1724 | ||
1725 | /* Direct connections between all NUMA nodes. */ | |
1726 | if (sched_numa_topology_type == NUMA_DIRECT) | |
1727 | return nid; | |
1728 | ||
1729 | /* | |
1730 | * On a system with glueless mesh NUMA topology, group_weight | |
1731 | * scores nodes according to the number of NUMA hinting faults on | |
1732 | * both the node itself, and on nearby nodes. | |
1733 | */ | |
1734 | if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { | |
1735 | unsigned long score, max_score = 0; | |
1736 | int node, max_node = nid; | |
1737 | ||
1738 | dist = sched_max_numa_distance; | |
1739 | ||
1740 | for_each_online_node(node) { | |
1741 | score = group_weight(p, node, dist); | |
1742 | if (score > max_score) { | |
1743 | max_score = score; | |
1744 | max_node = node; | |
1745 | } | |
1746 | } | |
1747 | return max_node; | |
1748 | } | |
1749 | ||
1750 | /* | |
1751 | * Finding the preferred nid in a system with NUMA backplane | |
1752 | * interconnect topology is more involved. The goal is to locate | |
1753 | * tasks from numa_groups near each other in the system, and | |
1754 | * untangle workloads from different sides of the system. This requires | |
1755 | * searching down the hierarchy of node groups, recursively searching | |
1756 | * inside the highest scoring group of nodes. The nodemask tricks | |
1757 | * keep the complexity of the search down. | |
1758 | */ | |
1759 | nodes = node_online_map; | |
1760 | for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) { | |
1761 | unsigned long max_faults = 0; | |
1762 | nodemask_t max_group = NODE_MASK_NONE; | |
1763 | int a, b; | |
1764 | ||
1765 | /* Are there nodes at this distance from each other? */ | |
1766 | if (!find_numa_distance(dist)) | |
1767 | continue; | |
1768 | ||
1769 | for_each_node_mask(a, nodes) { | |
1770 | unsigned long faults = 0; | |
1771 | nodemask_t this_group; | |
1772 | nodes_clear(this_group); | |
1773 | ||
1774 | /* Sum group's NUMA faults; includes a==b case. */ | |
1775 | for_each_node_mask(b, nodes) { | |
1776 | if (node_distance(a, b) < dist) { | |
1777 | faults += group_faults(p, b); | |
1778 | node_set(b, this_group); | |
1779 | node_clear(b, nodes); | |
1780 | } | |
1781 | } | |
1782 | ||
1783 | /* Remember the top group. */ | |
1784 | if (faults > max_faults) { | |
1785 | max_faults = faults; | |
1786 | max_group = this_group; | |
1787 | /* | |
1788 | * subtle: at the smallest distance there is | |
1789 | * just one node left in each "group", the | |
1790 | * winner is the preferred nid. | |
1791 | */ | |
1792 | nid = a; | |
1793 | } | |
1794 | } | |
1795 | /* Next round, evaluate the nodes within max_group. */ | |
1796 | if (!max_faults) | |
1797 | break; | |
1798 | nodes = max_group; | |
1799 | } | |
1800 | return nid; | |
1801 | } | |
1802 | ||
1803 | static void task_numa_placement(struct task_struct *p) | |
1804 | { | |
1805 | int seq, nid, max_nid = -1, max_group_nid = -1; | |
1806 | unsigned long max_faults = 0, max_group_faults = 0; | |
1807 | unsigned long fault_types[2] = { 0, 0 }; | |
1808 | unsigned long total_faults; | |
1809 | u64 runtime, period; | |
1810 | spinlock_t *group_lock = NULL; | |
1811 | ||
1812 | /* | |
1813 | * The p->mm->numa_scan_seq field gets updated without | |
1814 | * exclusive access. Use READ_ONCE() here to ensure | |
1815 | * that the field is read in a single access: | |
1816 | */ | |
1817 | seq = READ_ONCE(p->mm->numa_scan_seq); | |
1818 | if (p->numa_scan_seq == seq) | |
1819 | return; | |
1820 | p->numa_scan_seq = seq; | |
1821 | p->numa_scan_period_max = task_scan_max(p); | |
1822 | ||
1823 | total_faults = p->numa_faults_locality[0] + | |
1824 | p->numa_faults_locality[1]; | |
1825 | runtime = numa_get_avg_runtime(p, &period); | |
1826 | ||
1827 | /* If the task is part of a group prevent parallel updates to group stats */ | |
1828 | if (p->numa_group) { | |
1829 | group_lock = &p->numa_group->lock; | |
1830 | spin_lock_irq(group_lock); | |
1831 | } | |
1832 | ||
1833 | /* Find the node with the highest number of faults */ | |
1834 | for_each_online_node(nid) { | |
1835 | /* Keep track of the offsets in numa_faults array */ | |
1836 | int mem_idx, membuf_idx, cpu_idx, cpubuf_idx; | |
1837 | unsigned long faults = 0, group_faults = 0; | |
1838 | int priv; | |
1839 | ||
1840 | for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) { | |
1841 | long diff, f_diff, f_weight; | |
1842 | ||
1843 | mem_idx = task_faults_idx(NUMA_MEM, nid, priv); | |
1844 | membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv); | |
1845 | cpu_idx = task_faults_idx(NUMA_CPU, nid, priv); | |
1846 | cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv); | |
1847 | ||
1848 | /* Decay existing window, copy faults since last scan */ | |
1849 | diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2; | |
1850 | fault_types[priv] += p->numa_faults[membuf_idx]; | |
1851 | p->numa_faults[membuf_idx] = 0; | |
1852 | ||
1853 | /* | |
1854 | * Normalize the faults_from, so all tasks in a group | |
1855 | * count according to CPU use, instead of by the raw | |
1856 | * number of faults. Tasks with little runtime have | |
1857 | * little over-all impact on throughput, and thus their | |
1858 | * faults are less important. | |
1859 | */ | |
1860 | f_weight = div64_u64(runtime << 16, period + 1); | |
1861 | f_weight = (f_weight * p->numa_faults[cpubuf_idx]) / | |
1862 | (total_faults + 1); | |
1863 | f_diff = f_weight - p->numa_faults[cpu_idx] / 2; | |
1864 | p->numa_faults[cpubuf_idx] = 0; | |
1865 | ||
1866 | p->numa_faults[mem_idx] += diff; | |
1867 | p->numa_faults[cpu_idx] += f_diff; | |
1868 | faults += p->numa_faults[mem_idx]; | |
1869 | p->total_numa_faults += diff; | |
1870 | if (p->numa_group) { | |
1871 | /* | |
1872 | * safe because we can only change our own group | |
1873 | * | |
1874 | * mem_idx represents the offset for a given | |
1875 | * nid and priv in a specific region because it | |
1876 | * is at the beginning of the numa_faults array. | |
1877 | */ | |
1878 | p->numa_group->faults[mem_idx] += diff; | |
1879 | p->numa_group->faults_cpu[mem_idx] += f_diff; | |
1880 | p->numa_group->total_faults += diff; | |
1881 | group_faults += p->numa_group->faults[mem_idx]; | |
1882 | } | |
1883 | } | |
1884 | ||
1885 | if (faults > max_faults) { | |
1886 | max_faults = faults; | |
1887 | max_nid = nid; | |
1888 | } | |
1889 | ||
1890 | if (group_faults > max_group_faults) { | |
1891 | max_group_faults = group_faults; | |
1892 | max_group_nid = nid; | |
1893 | } | |
1894 | } | |
1895 | ||
1896 | update_task_scan_period(p, fault_types[0], fault_types[1]); | |
1897 | ||
1898 | if (p->numa_group) { | |
1899 | update_numa_active_node_mask(p->numa_group); | |
1900 | spin_unlock_irq(group_lock); | |
1901 | max_nid = preferred_group_nid(p, max_group_nid); | |
1902 | } | |
1903 | ||
1904 | if (max_faults) { | |
1905 | /* Set the new preferred node */ | |
1906 | if (max_nid != p->numa_preferred_nid) | |
1907 | sched_setnuma(p, max_nid); | |
1908 | ||
1909 | if (task_node(p) != p->numa_preferred_nid) | |
1910 | numa_migrate_preferred(p); | |
1911 | } | |
1912 | } | |
1913 | ||
1914 | static inline int get_numa_group(struct numa_group *grp) | |
1915 | { | |
1916 | return atomic_inc_not_zero(&grp->refcount); | |
1917 | } | |
1918 | ||
1919 | static inline void put_numa_group(struct numa_group *grp) | |
1920 | { | |
1921 | if (atomic_dec_and_test(&grp->refcount)) | |
1922 | kfree_rcu(grp, rcu); | |
1923 | } | |
1924 | ||
1925 | static void task_numa_group(struct task_struct *p, int cpupid, int flags, | |
1926 | int *priv) | |
1927 | { | |
1928 | struct numa_group *grp, *my_grp; | |
1929 | struct task_struct *tsk; | |
1930 | bool join = false; | |
1931 | int cpu = cpupid_to_cpu(cpupid); | |
1932 | int i; | |
1933 | ||
1934 | if (unlikely(!p->numa_group)) { | |
1935 | unsigned int size = sizeof(struct numa_group) + | |
1936 | 4*nr_node_ids*sizeof(unsigned long); | |
1937 | ||
1938 | grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); | |
1939 | if (!grp) | |
1940 | return; | |
1941 | ||
1942 | atomic_set(&grp->refcount, 1); | |
1943 | spin_lock_init(&grp->lock); | |
1944 | grp->gid = p->pid; | |
1945 | /* Second half of the array tracks nids where faults happen */ | |
1946 | grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES * | |
1947 | nr_node_ids; | |
1948 | ||
1949 | node_set(task_node(current), grp->active_nodes); | |
1950 | ||
1951 | for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) | |
1952 | grp->faults[i] = p->numa_faults[i]; | |
1953 | ||
1954 | grp->total_faults = p->total_numa_faults; | |
1955 | ||
1956 | grp->nr_tasks++; | |
1957 | rcu_assign_pointer(p->numa_group, grp); | |
1958 | } | |
1959 | ||
1960 | rcu_read_lock(); | |
1961 | tsk = READ_ONCE(cpu_rq(cpu)->curr); | |
1962 | ||
1963 | if (!cpupid_match_pid(tsk, cpupid)) | |
1964 | goto no_join; | |
1965 | ||
1966 | grp = rcu_dereference(tsk->numa_group); | |
1967 | if (!grp) | |
1968 | goto no_join; | |
1969 | ||
1970 | my_grp = p->numa_group; | |
1971 | if (grp == my_grp) | |
1972 | goto no_join; | |
1973 | ||
1974 | /* | |
1975 | * Only join the other group if its bigger; if we're the bigger group, | |
1976 | * the other task will join us. | |
1977 | */ | |
1978 | if (my_grp->nr_tasks > grp->nr_tasks) | |
1979 | goto no_join; | |
1980 | ||
1981 | /* | |
1982 | * Tie-break on the grp address. | |
1983 | */ | |
1984 | if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp) | |
1985 | goto no_join; | |
1986 | ||
1987 | /* Always join threads in the same process. */ | |
1988 | if (tsk->mm == current->mm) | |
1989 | join = true; | |
1990 | ||
1991 | /* Simple filter to avoid false positives due to PID collisions */ | |
1992 | if (flags & TNF_SHARED) | |
1993 | join = true; | |
1994 | ||
1995 | /* Update priv based on whether false sharing was detected */ | |
1996 | *priv = !join; | |
1997 | ||
1998 | if (join && !get_numa_group(grp)) | |
1999 | goto no_join; | |
2000 | ||
2001 | rcu_read_unlock(); | |
2002 | ||
2003 | if (!join) | |
2004 | return; | |
2005 | ||
2006 | BUG_ON(irqs_disabled()); | |
2007 | double_lock_irq(&my_grp->lock, &grp->lock); | |
2008 | ||
2009 | for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) { | |
2010 | my_grp->faults[i] -= p->numa_faults[i]; | |
2011 | grp->faults[i] += p->numa_faults[i]; | |
2012 | } | |
2013 | my_grp->total_faults -= p->total_numa_faults; | |
2014 | grp->total_faults += p->total_numa_faults; | |
2015 | ||
2016 | my_grp->nr_tasks--; | |
2017 | grp->nr_tasks++; | |
2018 | ||
2019 | spin_unlock(&my_grp->lock); | |
2020 | spin_unlock_irq(&grp->lock); | |
2021 | ||
2022 | rcu_assign_pointer(p->numa_group, grp); | |
2023 | ||
2024 | put_numa_group(my_grp); | |
2025 | return; | |
2026 | ||
2027 | no_join: | |
2028 | rcu_read_unlock(); | |
2029 | return; | |
2030 | } | |
2031 | ||
2032 | void task_numa_free(struct task_struct *p) | |
2033 | { | |
2034 | struct numa_group *grp = p->numa_group; | |
2035 | void *numa_faults = p->numa_faults; | |
2036 | unsigned long flags; | |
2037 | int i; | |
2038 | ||
2039 | if (grp) { | |
2040 | spin_lock_irqsave(&grp->lock, flags); | |
2041 | for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) | |
2042 | grp->faults[i] -= p->numa_faults[i]; | |
2043 | grp->total_faults -= p->total_numa_faults; | |
2044 | ||
2045 | grp->nr_tasks--; | |
2046 | spin_unlock_irqrestore(&grp->lock, flags); | |
2047 | RCU_INIT_POINTER(p->numa_group, NULL); | |
2048 | put_numa_group(grp); | |
2049 | } | |
2050 | ||
2051 | p->numa_faults = NULL; | |
2052 | kfree(numa_faults); | |
2053 | } | |
2054 | ||
2055 | /* | |
2056 | * Got a PROT_NONE fault for a page on @node. | |
2057 | */ | |
2058 | void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) | |
2059 | { | |
2060 | struct task_struct *p = current; | |
2061 | bool migrated = flags & TNF_MIGRATED; | |
2062 | int cpu_node = task_node(current); | |
2063 | int local = !!(flags & TNF_FAULT_LOCAL); | |
2064 | int priv; | |
2065 | ||
2066 | if (!numabalancing_enabled) | |
2067 | return; | |
2068 | ||
2069 | /* for example, ksmd faulting in a user's mm */ | |
2070 | if (!p->mm) | |
2071 | return; | |
2072 | ||
2073 | /* Allocate buffer to track faults on a per-node basis */ | |
2074 | if (unlikely(!p->numa_faults)) { | |
2075 | int size = sizeof(*p->numa_faults) * | |
2076 | NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids; | |
2077 | ||
2078 | p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN); | |
2079 | if (!p->numa_faults) | |
2080 | return; | |
2081 | ||
2082 | p->total_numa_faults = 0; | |
2083 | memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); | |
2084 | } | |
2085 | ||
2086 | /* | |
2087 | * First accesses are treated as private, otherwise consider accesses | |
2088 | * to be private if the accessing pid has not changed | |
2089 | */ | |
2090 | if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { | |
2091 | priv = 1; | |
2092 | } else { | |
2093 | priv = cpupid_match_pid(p, last_cpupid); | |
2094 | if (!priv && !(flags & TNF_NO_GROUP)) | |
2095 | task_numa_group(p, last_cpupid, flags, &priv); | |
2096 | } | |
2097 | ||
2098 | /* | |
2099 | * If a workload spans multiple NUMA nodes, a shared fault that | |
2100 | * occurs wholly within the set of nodes that the workload is | |
2101 | * actively using should be counted as local. This allows the | |
2102 | * scan rate to slow down when a workload has settled down. | |
2103 | */ | |
2104 | if (!priv && !local && p->numa_group && | |
2105 | node_isset(cpu_node, p->numa_group->active_nodes) && | |
2106 | node_isset(mem_node, p->numa_group->active_nodes)) | |
2107 | local = 1; | |
2108 | ||
2109 | task_numa_placement(p); | |
2110 | ||
2111 | /* | |
2112 | * Retry task to preferred node migration periodically, in case it | |
2113 | * case it previously failed, or the scheduler moved us. | |
2114 | */ | |
2115 | if (time_after(jiffies, p->numa_migrate_retry)) | |
2116 | numa_migrate_preferred(p); | |
2117 | ||
2118 | if (migrated) | |
2119 | p->numa_pages_migrated += pages; | |
2120 | if (flags & TNF_MIGRATE_FAIL) | |
2121 | p->numa_faults_locality[2] += pages; | |
2122 | ||
2123 | p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages; | |
2124 | p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages; | |
2125 | p->numa_faults_locality[local] += pages; | |
2126 | } | |
2127 | ||
2128 | static void reset_ptenuma_scan(struct task_struct *p) | |
2129 | { | |
2130 | /* | |
2131 | * We only did a read acquisition of the mmap sem, so | |
2132 | * p->mm->numa_scan_seq is written to without exclusive access | |
2133 | * and the update is not guaranteed to be atomic. That's not | |
2134 | * much of an issue though, since this is just used for | |
2135 | * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not | |
2136 | * expensive, to avoid any form of compiler optimizations: | |
2137 | */ | |
2138 | WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1); | |
2139 | p->mm->numa_scan_offset = 0; | |
2140 | } | |
2141 | ||
2142 | /* | |
2143 | * The expensive part of numa migration is done from task_work context. | |
2144 | * Triggered from task_tick_numa(). | |
2145 | */ | |
2146 | void task_numa_work(struct callback_head *work) | |
2147 | { | |
2148 | unsigned long migrate, next_scan, now = jiffies; | |
2149 | struct task_struct *p = current; | |
2150 | struct mm_struct *mm = p->mm; | |
2151 | struct vm_area_struct *vma; | |
2152 | unsigned long start, end; | |
2153 | unsigned long nr_pte_updates = 0; | |
2154 | long pages; | |
2155 | ||
2156 | WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work)); | |
2157 | ||
2158 | work->next = work; /* protect against double add */ | |
2159 | /* | |
2160 | * Who cares about NUMA placement when they're dying. | |
2161 | * | |
2162 | * NOTE: make sure not to dereference p->mm before this check, | |
2163 | * exit_task_work() happens _after_ exit_mm() so we could be called | |
2164 | * without p->mm even though we still had it when we enqueued this | |
2165 | * work. | |
2166 | */ | |
2167 | if (p->flags & PF_EXITING) | |
2168 | return; | |
2169 | ||
2170 | if (!mm->numa_next_scan) { | |
2171 | mm->numa_next_scan = now + | |
2172 | msecs_to_jiffies(sysctl_numa_balancing_scan_delay); | |
2173 | } | |
2174 | ||
2175 | /* | |
2176 | * Enforce maximal scan/migration frequency.. | |
2177 | */ | |
2178 | migrate = mm->numa_next_scan; | |
2179 | if (time_before(now, migrate)) | |
2180 | return; | |
2181 | ||
2182 | if (p->numa_scan_period == 0) { | |
2183 | p->numa_scan_period_max = task_scan_max(p); | |
2184 | p->numa_scan_period = task_scan_min(p); | |
2185 | } | |
2186 | ||
2187 | next_scan = now + msecs_to_jiffies(p->numa_scan_period); | |
2188 | if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate) | |
2189 | return; | |
2190 | ||
2191 | /* | |
2192 | * Delay this task enough that another task of this mm will likely win | |
2193 | * the next time around. | |
2194 | */ | |
2195 | p->node_stamp += 2 * TICK_NSEC; | |
2196 | ||
2197 | start = mm->numa_scan_offset; | |
2198 | pages = sysctl_numa_balancing_scan_size; | |
2199 | pages <<= 20 - PAGE_SHIFT; /* MB in pages */ | |
2200 | if (!pages) | |
2201 | return; | |
2202 | ||
2203 | down_read(&mm->mmap_sem); | |
2204 | vma = find_vma(mm, start); | |
2205 | if (!vma) { | |
2206 | reset_ptenuma_scan(p); | |
2207 | start = 0; | |
2208 | vma = mm->mmap; | |
2209 | } | |
2210 | for (; vma; vma = vma->vm_next) { | |
2211 | if (!vma_migratable(vma) || !vma_policy_mof(vma) || | |
2212 | is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) { | |
2213 | continue; | |
2214 | } | |
2215 | ||
2216 | /* | |
2217 | * Shared library pages mapped by multiple processes are not | |
2218 | * migrated as it is expected they are cache replicated. Avoid | |
2219 | * hinting faults in read-only file-backed mappings or the vdso | |
2220 | * as migrating the pages will be of marginal benefit. | |
2221 | */ | |
2222 | if (!vma->vm_mm || | |
2223 | (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) | |
2224 | continue; | |
2225 | ||
2226 | /* | |
2227 | * Skip inaccessible VMAs to avoid any confusion between | |
2228 | * PROT_NONE and NUMA hinting ptes | |
2229 | */ | |
2230 | if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) | |
2231 | continue; | |
2232 | ||
2233 | do { | |
2234 | start = max(start, vma->vm_start); | |
2235 | end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); | |
2236 | end = min(end, vma->vm_end); | |
2237 | nr_pte_updates += change_prot_numa(vma, start, end); | |
2238 | ||
2239 | /* | |
2240 | * Scan sysctl_numa_balancing_scan_size but ensure that | |
2241 | * at least one PTE is updated so that unused virtual | |
2242 | * address space is quickly skipped. | |
2243 | */ | |
2244 | if (nr_pte_updates) | |
2245 | pages -= (end - start) >> PAGE_SHIFT; | |
2246 | ||
2247 | start = end; | |
2248 | if (pages <= 0) | |
2249 | goto out; | |
2250 | ||
2251 | cond_resched(); | |
2252 | } while (end != vma->vm_end); | |
2253 | } | |
2254 | ||
2255 | out: | |
2256 | /* | |
2257 | * It is possible to reach the end of the VMA list but the last few | |
2258 | * VMAs are not guaranteed to the vma_migratable. If they are not, we | |
2259 | * would find the !migratable VMA on the next scan but not reset the | |
2260 | * scanner to the start so check it now. | |
2261 | */ | |
2262 | if (vma) | |
2263 | mm->numa_scan_offset = start; | |
2264 | else | |
2265 | reset_ptenuma_scan(p); | |
2266 | up_read(&mm->mmap_sem); | |
2267 | } | |
2268 | ||
2269 | /* | |
2270 | * Drive the periodic memory faults.. | |
2271 | */ | |
2272 | void task_tick_numa(struct rq *rq, struct task_struct *curr) | |
2273 | { | |
2274 | struct callback_head *work = &curr->numa_work; | |
2275 | u64 period, now; | |
2276 | ||
2277 | /* | |
2278 | * We don't care about NUMA placement if we don't have memory. | |
2279 | */ | |
2280 | if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work) | |
2281 | return; | |
2282 | ||
2283 | /* | |
2284 | * Using runtime rather than walltime has the dual advantage that | |
2285 | * we (mostly) drive the selection from busy threads and that the | |
2286 | * task needs to have done some actual work before we bother with | |
2287 | * NUMA placement. | |
2288 | */ | |
2289 | now = curr->se.sum_exec_runtime; | |
2290 | period = (u64)curr->numa_scan_period * NSEC_PER_MSEC; | |
2291 | ||
2292 | if (now - curr->node_stamp > period) { | |
2293 | if (!curr->node_stamp) | |
2294 | curr->numa_scan_period = task_scan_min(curr); | |
2295 | curr->node_stamp += period; | |
2296 | ||
2297 | if (!time_before(jiffies, curr->mm->numa_next_scan)) { | |
2298 | init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */ | |
2299 | task_work_add(curr, work, true); | |
2300 | } | |
2301 | } | |
2302 | } | |
2303 | #else | |
2304 | static void task_tick_numa(struct rq *rq, struct task_struct *curr) | |
2305 | { | |
2306 | } | |
2307 | ||
2308 | static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p) | |
2309 | { | |
2310 | } | |
2311 | ||
2312 | static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p) | |
2313 | { | |
2314 | } | |
2315 | #endif /* CONFIG_NUMA_BALANCING */ | |
2316 | ||
2317 | static void | |
2318 | account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
2319 | { | |
2320 | update_load_add(&cfs_rq->load, se->load.weight); | |
2321 | if (!parent_entity(se)) | |
2322 | update_load_add(&rq_of(cfs_rq)->load, se->load.weight); | |
2323 | #ifdef CONFIG_SMP | |
2324 | if (entity_is_task(se)) { | |
2325 | struct rq *rq = rq_of(cfs_rq); | |
2326 | ||
2327 | account_numa_enqueue(rq, task_of(se)); | |
2328 | list_add(&se->group_node, &rq->cfs_tasks); | |
2329 | } | |
2330 | #endif | |
2331 | cfs_rq->nr_running++; | |
2332 | } | |
2333 | ||
2334 | static void | |
2335 | account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
2336 | { | |
2337 | update_load_sub(&cfs_rq->load, se->load.weight); | |
2338 | if (!parent_entity(se)) | |
2339 | update_load_sub(&rq_of(cfs_rq)->load, se->load.weight); | |
2340 | if (entity_is_task(se)) { | |
2341 | account_numa_dequeue(rq_of(cfs_rq), task_of(se)); | |
2342 | list_del_init(&se->group_node); | |
2343 | } | |
2344 | cfs_rq->nr_running--; | |
2345 | } | |
2346 | ||
2347 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
2348 | # ifdef CONFIG_SMP | |
2349 | static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq) | |
2350 | { | |
2351 | long tg_weight; | |
2352 | ||
2353 | /* | |
2354 | * Use this CPU's actual weight instead of the last load_contribution | |
2355 | * to gain a more accurate current total weight. See | |
2356 | * update_cfs_rq_load_contribution(). | |
2357 | */ | |
2358 | tg_weight = atomic_long_read(&tg->load_avg); | |
2359 | tg_weight -= cfs_rq->tg_load_contrib; | |
2360 | tg_weight += cfs_rq->load.weight; | |
2361 | ||
2362 | return tg_weight; | |
2363 | } | |
2364 | ||
2365 | static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) | |
2366 | { | |
2367 | long tg_weight, load, shares; | |
2368 | ||
2369 | tg_weight = calc_tg_weight(tg, cfs_rq); | |
2370 | load = cfs_rq->load.weight; | |
2371 | ||
2372 | shares = (tg->shares * load); | |
2373 | if (tg_weight) | |
2374 | shares /= tg_weight; | |
2375 | ||
2376 | if (shares < MIN_SHARES) | |
2377 | shares = MIN_SHARES; | |
2378 | if (shares > tg->shares) | |
2379 | shares = tg->shares; | |
2380 | ||
2381 | return shares; | |
2382 | } | |
2383 | # else /* CONFIG_SMP */ | |
2384 | static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) | |
2385 | { | |
2386 | return tg->shares; | |
2387 | } | |
2388 | # endif /* CONFIG_SMP */ | |
2389 | static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, | |
2390 | unsigned long weight) | |
2391 | { | |
2392 | if (se->on_rq) { | |
2393 | /* commit outstanding execution time */ | |
2394 | if (cfs_rq->curr == se) | |
2395 | update_curr(cfs_rq); | |
2396 | account_entity_dequeue(cfs_rq, se); | |
2397 | } | |
2398 | ||
2399 | update_load_set(&se->load, weight); | |
2400 | ||
2401 | if (se->on_rq) | |
2402 | account_entity_enqueue(cfs_rq, se); | |
2403 | } | |
2404 | ||
2405 | static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); | |
2406 | ||
2407 | static void update_cfs_shares(struct cfs_rq *cfs_rq) | |
2408 | { | |
2409 | struct task_group *tg; | |
2410 | struct sched_entity *se; | |
2411 | long shares; | |
2412 | ||
2413 | tg = cfs_rq->tg; | |
2414 | se = tg->se[cpu_of(rq_of(cfs_rq))]; | |
2415 | if (!se || throttled_hierarchy(cfs_rq)) | |
2416 | return; | |
2417 | #ifndef CONFIG_SMP | |
2418 | if (likely(se->load.weight == tg->shares)) | |
2419 | return; | |
2420 | #endif | |
2421 | shares = calc_cfs_shares(cfs_rq, tg); | |
2422 | ||
2423 | reweight_entity(cfs_rq_of(se), se, shares); | |
2424 | } | |
2425 | #else /* CONFIG_FAIR_GROUP_SCHED */ | |
2426 | static inline void update_cfs_shares(struct cfs_rq *cfs_rq) | |
2427 | { | |
2428 | } | |
2429 | #endif /* CONFIG_FAIR_GROUP_SCHED */ | |
2430 | ||
2431 | #ifdef CONFIG_SMP | |
2432 | /* | |
2433 | * We choose a half-life close to 1 scheduling period. | |
2434 | * Note: The tables below are dependent on this value. | |
2435 | */ | |
2436 | #define LOAD_AVG_PERIOD 32 | |
2437 | #define LOAD_AVG_MAX 47742 /* maximum possible load avg */ | |
2438 | #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */ | |
2439 | ||
2440 | /* Precomputed fixed inverse multiplies for multiplication by y^n */ | |
2441 | static const u32 runnable_avg_yN_inv[] = { | |
2442 | 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6, | |
2443 | 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85, | |
2444 | 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581, | |
2445 | 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9, | |
2446 | 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80, | |
2447 | 0x85aac367, 0x82cd8698, | |
2448 | }; | |
2449 | ||
2450 | /* | |
2451 | * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent | |
2452 | * over-estimates when re-combining. | |
2453 | */ | |
2454 | static const u32 runnable_avg_yN_sum[] = { | |
2455 | 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103, | |
2456 | 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082, | |
2457 | 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371, | |
2458 | }; | |
2459 | ||
2460 | /* | |
2461 | * Approximate: | |
2462 | * val * y^n, where y^32 ~= 0.5 (~1 scheduling period) | |
2463 | */ | |
2464 | static __always_inline u64 decay_load(u64 val, u64 n) | |
2465 | { | |
2466 | unsigned int local_n; | |
2467 | ||
2468 | if (!n) | |
2469 | return val; | |
2470 | else if (unlikely(n > LOAD_AVG_PERIOD * 63)) | |
2471 | return 0; | |
2472 | ||
2473 | /* after bounds checking we can collapse to 32-bit */ | |
2474 | local_n = n; | |
2475 | ||
2476 | /* | |
2477 | * As y^PERIOD = 1/2, we can combine | |
2478 | * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD) | |
2479 | * With a look-up table which covers y^n (n<PERIOD) | |
2480 | * | |
2481 | * To achieve constant time decay_load. | |
2482 | */ | |
2483 | if (unlikely(local_n >= LOAD_AVG_PERIOD)) { | |
2484 | val >>= local_n / LOAD_AVG_PERIOD; | |
2485 | local_n %= LOAD_AVG_PERIOD; | |
2486 | } | |
2487 | ||
2488 | val *= runnable_avg_yN_inv[local_n]; | |
2489 | /* We don't use SRR here since we always want to round down. */ | |
2490 | return val >> 32; | |
2491 | } | |
2492 | ||
2493 | /* | |
2494 | * For updates fully spanning n periods, the contribution to runnable | |
2495 | * average will be: \Sum 1024*y^n | |
2496 | * | |
2497 | * We can compute this reasonably efficiently by combining: | |
2498 | * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD} | |
2499 | */ | |
2500 | static u32 __compute_runnable_contrib(u64 n) | |
2501 | { | |
2502 | u32 contrib = 0; | |
2503 | ||
2504 | if (likely(n <= LOAD_AVG_PERIOD)) | |
2505 | return runnable_avg_yN_sum[n]; | |
2506 | else if (unlikely(n >= LOAD_AVG_MAX_N)) | |
2507 | return LOAD_AVG_MAX; | |
2508 | ||
2509 | /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */ | |
2510 | do { | |
2511 | contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */ | |
2512 | contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD]; | |
2513 | ||
2514 | n -= LOAD_AVG_PERIOD; | |
2515 | } while (n > LOAD_AVG_PERIOD); | |
2516 | ||
2517 | contrib = decay_load(contrib, n); | |
2518 | return contrib + runnable_avg_yN_sum[n]; | |
2519 | } | |
2520 | ||
2521 | /* | |
2522 | * We can represent the historical contribution to runnable average as the | |
2523 | * coefficients of a geometric series. To do this we sub-divide our runnable | |
2524 | * history into segments of approximately 1ms (1024us); label the segment that | |
2525 | * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g. | |
2526 | * | |
2527 | * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ... | |
2528 | * p0 p1 p2 | |
2529 | * (now) (~1ms ago) (~2ms ago) | |
2530 | * | |
2531 | * Let u_i denote the fraction of p_i that the entity was runnable. | |
2532 | * | |
2533 | * We then designate the fractions u_i as our co-efficients, yielding the | |
2534 | * following representation of historical load: | |
2535 | * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ... | |
2536 | * | |
2537 | * We choose y based on the with of a reasonably scheduling period, fixing: | |
2538 | * y^32 = 0.5 | |
2539 | * | |
2540 | * This means that the contribution to load ~32ms ago (u_32) will be weighted | |
2541 | * approximately half as much as the contribution to load within the last ms | |
2542 | * (u_0). | |
2543 | * | |
2544 | * When a period "rolls over" and we have new u_0`, multiplying the previous | |
2545 | * sum again by y is sufficient to update: | |
2546 | * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... ) | |
2547 | * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}] | |
2548 | */ | |
2549 | static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, | |
2550 | struct sched_avg *sa, | |
2551 | int runnable, | |
2552 | int running) | |
2553 | { | |
2554 | u64 delta, periods; | |
2555 | u32 runnable_contrib; | |
2556 | int delta_w, decayed = 0; | |
2557 | unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu); | |
2558 | ||
2559 | delta = now - sa->last_runnable_update; | |
2560 | /* | |
2561 | * This should only happen when time goes backwards, which it | |
2562 | * unfortunately does during sched clock init when we swap over to TSC. | |
2563 | */ | |
2564 | if ((s64)delta < 0) { | |
2565 | sa->last_runnable_update = now; | |
2566 | return 0; | |
2567 | } | |
2568 | ||
2569 | /* | |
2570 | * Use 1024ns as the unit of measurement since it's a reasonable | |
2571 | * approximation of 1us and fast to compute. | |
2572 | */ | |
2573 | delta >>= 10; | |
2574 | if (!delta) | |
2575 | return 0; | |
2576 | sa->last_runnable_update = now; | |
2577 | ||
2578 | /* delta_w is the amount already accumulated against our next period */ | |
2579 | delta_w = sa->avg_period % 1024; | |
2580 | if (delta + delta_w >= 1024) { | |
2581 | /* period roll-over */ | |
2582 | decayed = 1; | |
2583 | ||
2584 | /* | |
2585 | * Now that we know we're crossing a period boundary, figure | |
2586 | * out how much from delta we need to complete the current | |
2587 | * period and accrue it. | |
2588 | */ | |
2589 | delta_w = 1024 - delta_w; | |
2590 | if (runnable) | |
2591 | sa->runnable_avg_sum += delta_w; | |
2592 | if (running) | |
2593 | sa->running_avg_sum += delta_w * scale_freq | |
2594 | >> SCHED_CAPACITY_SHIFT; | |
2595 | sa->avg_period += delta_w; | |
2596 | ||
2597 | delta -= delta_w; | |
2598 | ||
2599 | /* Figure out how many additional periods this update spans */ | |
2600 | periods = delta / 1024; | |
2601 | delta %= 1024; | |
2602 | ||
2603 | sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum, | |
2604 | periods + 1); | |
2605 | sa->running_avg_sum = decay_load(sa->running_avg_sum, | |
2606 | periods + 1); | |
2607 | sa->avg_period = decay_load(sa->avg_period, | |
2608 | periods + 1); | |
2609 | ||
2610 | /* Efficiently calculate \sum (1..n_period) 1024*y^i */ | |
2611 | runnable_contrib = __compute_runnable_contrib(periods); | |
2612 | if (runnable) | |
2613 | sa->runnable_avg_sum += runnable_contrib; | |
2614 | if (running) | |
2615 | sa->running_avg_sum += runnable_contrib * scale_freq | |
2616 | >> SCHED_CAPACITY_SHIFT; | |
2617 | sa->avg_period += runnable_contrib; | |
2618 | } | |
2619 | ||
2620 | /* Remainder of delta accrued against u_0` */ | |
2621 | if (runnable) | |
2622 | sa->runnable_avg_sum += delta; | |
2623 | if (running) | |
2624 | sa->running_avg_sum += delta * scale_freq | |
2625 | >> SCHED_CAPACITY_SHIFT; | |
2626 | sa->avg_period += delta; | |
2627 | ||
2628 | return decayed; | |
2629 | } | |
2630 | ||
2631 | /* Synchronize an entity's decay with its parenting cfs_rq.*/ | |
2632 | static inline u64 __synchronize_entity_decay(struct sched_entity *se) | |
2633 | { | |
2634 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
2635 | u64 decays = atomic64_read(&cfs_rq->decay_counter); | |
2636 | ||
2637 | decays -= se->avg.decay_count; | |
2638 | se->avg.decay_count = 0; | |
2639 | if (!decays) | |
2640 | return 0; | |
2641 | ||
2642 | se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays); | |
2643 | se->avg.utilization_avg_contrib = | |
2644 | decay_load(se->avg.utilization_avg_contrib, decays); | |
2645 | ||
2646 | return decays; | |
2647 | } | |
2648 | ||
2649 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
2650 | static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, | |
2651 | int force_update) | |
2652 | { | |
2653 | struct task_group *tg = cfs_rq->tg; | |
2654 | long tg_contrib; | |
2655 | ||
2656 | tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg; | |
2657 | tg_contrib -= cfs_rq->tg_load_contrib; | |
2658 | ||
2659 | if (!tg_contrib) | |
2660 | return; | |
2661 | ||
2662 | if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) { | |
2663 | atomic_long_add(tg_contrib, &tg->load_avg); | |
2664 | cfs_rq->tg_load_contrib += tg_contrib; | |
2665 | } | |
2666 | } | |
2667 | ||
2668 | /* | |
2669 | * Aggregate cfs_rq runnable averages into an equivalent task_group | |
2670 | * representation for computing load contributions. | |
2671 | */ | |
2672 | static inline void __update_tg_runnable_avg(struct sched_avg *sa, | |
2673 | struct cfs_rq *cfs_rq) | |
2674 | { | |
2675 | struct task_group *tg = cfs_rq->tg; | |
2676 | long contrib; | |
2677 | ||
2678 | /* The fraction of a cpu used by this cfs_rq */ | |
2679 | contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT, | |
2680 | sa->avg_period + 1); | |
2681 | contrib -= cfs_rq->tg_runnable_contrib; | |
2682 | ||
2683 | if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) { | |
2684 | atomic_add(contrib, &tg->runnable_avg); | |
2685 | cfs_rq->tg_runnable_contrib += contrib; | |
2686 | } | |
2687 | } | |
2688 | ||
2689 | static inline void __update_group_entity_contrib(struct sched_entity *se) | |
2690 | { | |
2691 | struct cfs_rq *cfs_rq = group_cfs_rq(se); | |
2692 | struct task_group *tg = cfs_rq->tg; | |
2693 | int runnable_avg; | |
2694 | ||
2695 | u64 contrib; | |
2696 | ||
2697 | contrib = cfs_rq->tg_load_contrib * tg->shares; | |
2698 | se->avg.load_avg_contrib = div_u64(contrib, | |
2699 | atomic_long_read(&tg->load_avg) + 1); | |
2700 | ||
2701 | /* | |
2702 | * For group entities we need to compute a correction term in the case | |
2703 | * that they are consuming <1 cpu so that we would contribute the same | |
2704 | * load as a task of equal weight. | |
2705 | * | |
2706 | * Explicitly co-ordinating this measurement would be expensive, but | |
2707 | * fortunately the sum of each cpus contribution forms a usable | |
2708 | * lower-bound on the true value. | |
2709 | * | |
2710 | * Consider the aggregate of 2 contributions. Either they are disjoint | |
2711 | * (and the sum represents true value) or they are disjoint and we are | |
2712 | * understating by the aggregate of their overlap. | |
2713 | * | |
2714 | * Extending this to N cpus, for a given overlap, the maximum amount we | |
2715 | * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of | |
2716 | * cpus that overlap for this interval and w_i is the interval width. | |
2717 | * | |
2718 | * On a small machine; the first term is well-bounded which bounds the | |
2719 | * total error since w_i is a subset of the period. Whereas on a | |
2720 | * larger machine, while this first term can be larger, if w_i is the | |
2721 | * of consequential size guaranteed to see n_i*w_i quickly converge to | |
2722 | * our upper bound of 1-cpu. | |
2723 | */ | |
2724 | runnable_avg = atomic_read(&tg->runnable_avg); | |
2725 | if (runnable_avg < NICE_0_LOAD) { | |
2726 | se->avg.load_avg_contrib *= runnable_avg; | |
2727 | se->avg.load_avg_contrib >>= NICE_0_SHIFT; | |
2728 | } | |
2729 | } | |
2730 | ||
2731 | static inline void update_rq_runnable_avg(struct rq *rq, int runnable) | |
2732 | { | |
2733 | __update_entity_runnable_avg(rq_clock_task(rq), cpu_of(rq), &rq->avg, | |
2734 | runnable, runnable); | |
2735 | __update_tg_runnable_avg(&rq->avg, &rq->cfs); | |
2736 | } | |
2737 | #else /* CONFIG_FAIR_GROUP_SCHED */ | |
2738 | static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, | |
2739 | int force_update) {} | |
2740 | static inline void __update_tg_runnable_avg(struct sched_avg *sa, | |
2741 | struct cfs_rq *cfs_rq) {} | |
2742 | static inline void __update_group_entity_contrib(struct sched_entity *se) {} | |
2743 | static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {} | |
2744 | #endif /* CONFIG_FAIR_GROUP_SCHED */ | |
2745 | ||
2746 | static inline void __update_task_entity_contrib(struct sched_entity *se) | |
2747 | { | |
2748 | u32 contrib; | |
2749 | ||
2750 | /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */ | |
2751 | contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight); | |
2752 | contrib /= (se->avg.avg_period + 1); | |
2753 | se->avg.load_avg_contrib = scale_load(contrib); | |
2754 | } | |
2755 | ||
2756 | /* Compute the current contribution to load_avg by se, return any delta */ | |
2757 | static long __update_entity_load_avg_contrib(struct sched_entity *se) | |
2758 | { | |
2759 | long old_contrib = se->avg.load_avg_contrib; | |
2760 | ||
2761 | if (entity_is_task(se)) { | |
2762 | __update_task_entity_contrib(se); | |
2763 | } else { | |
2764 | __update_tg_runnable_avg(&se->avg, group_cfs_rq(se)); | |
2765 | __update_group_entity_contrib(se); | |
2766 | } | |
2767 | ||
2768 | return se->avg.load_avg_contrib - old_contrib; | |
2769 | } | |
2770 | ||
2771 | ||
2772 | static inline void __update_task_entity_utilization(struct sched_entity *se) | |
2773 | { | |
2774 | u32 contrib; | |
2775 | ||
2776 | /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */ | |
2777 | contrib = se->avg.running_avg_sum * scale_load_down(SCHED_LOAD_SCALE); | |
2778 | contrib /= (se->avg.avg_period + 1); | |
2779 | se->avg.utilization_avg_contrib = scale_load(contrib); | |
2780 | } | |
2781 | ||
2782 | static long __update_entity_utilization_avg_contrib(struct sched_entity *se) | |
2783 | { | |
2784 | long old_contrib = se->avg.utilization_avg_contrib; | |
2785 | ||
2786 | if (entity_is_task(se)) | |
2787 | __update_task_entity_utilization(se); | |
2788 | else | |
2789 | se->avg.utilization_avg_contrib = | |
2790 | group_cfs_rq(se)->utilization_load_avg; | |
2791 | ||
2792 | return se->avg.utilization_avg_contrib - old_contrib; | |
2793 | } | |
2794 | ||
2795 | static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq, | |
2796 | long load_contrib) | |
2797 | { | |
2798 | if (likely(load_contrib < cfs_rq->blocked_load_avg)) | |
2799 | cfs_rq->blocked_load_avg -= load_contrib; | |
2800 | else | |
2801 | cfs_rq->blocked_load_avg = 0; | |
2802 | } | |
2803 | ||
2804 | static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq); | |
2805 | ||
2806 | /* Update a sched_entity's runnable average */ | |
2807 | static inline void update_entity_load_avg(struct sched_entity *se, | |
2808 | int update_cfs_rq) | |
2809 | { | |
2810 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
2811 | long contrib_delta, utilization_delta; | |
2812 | int cpu = cpu_of(rq_of(cfs_rq)); | |
2813 | u64 now; | |
2814 | ||
2815 | /* | |
2816 | * For a group entity we need to use their owned cfs_rq_clock_task() in | |
2817 | * case they are the parent of a throttled hierarchy. | |
2818 | */ | |
2819 | if (entity_is_task(se)) | |
2820 | now = cfs_rq_clock_task(cfs_rq); | |
2821 | else | |
2822 | now = cfs_rq_clock_task(group_cfs_rq(se)); | |
2823 | ||
2824 | if (!__update_entity_runnable_avg(now, cpu, &se->avg, se->on_rq, | |
2825 | cfs_rq->curr == se)) | |
2826 | return; | |
2827 | ||
2828 | contrib_delta = __update_entity_load_avg_contrib(se); | |
2829 | utilization_delta = __update_entity_utilization_avg_contrib(se); | |
2830 | ||
2831 | if (!update_cfs_rq) | |
2832 | return; | |
2833 | ||
2834 | if (se->on_rq) { | |
2835 | cfs_rq->runnable_load_avg += contrib_delta; | |
2836 | cfs_rq->utilization_load_avg += utilization_delta; | |
2837 | } else { | |
2838 | subtract_blocked_load_contrib(cfs_rq, -contrib_delta); | |
2839 | } | |
2840 | } | |
2841 | ||
2842 | /* | |
2843 | * Decay the load contributed by all blocked children and account this so that | |
2844 | * their contribution may appropriately discounted when they wake up. | |
2845 | */ | |
2846 | static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update) | |
2847 | { | |
2848 | u64 now = cfs_rq_clock_task(cfs_rq) >> 20; | |
2849 | u64 decays; | |
2850 | ||
2851 | decays = now - cfs_rq->last_decay; | |
2852 | if (!decays && !force_update) | |
2853 | return; | |
2854 | ||
2855 | if (atomic_long_read(&cfs_rq->removed_load)) { | |
2856 | unsigned long removed_load; | |
2857 | removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0); | |
2858 | subtract_blocked_load_contrib(cfs_rq, removed_load); | |
2859 | } | |
2860 | ||
2861 | if (decays) { | |
2862 | cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg, | |
2863 | decays); | |
2864 | atomic64_add(decays, &cfs_rq->decay_counter); | |
2865 | cfs_rq->last_decay = now; | |
2866 | } | |
2867 | ||
2868 | __update_cfs_rq_tg_load_contrib(cfs_rq, force_update); | |
2869 | } | |
2870 | ||
2871 | /* Add the load generated by se into cfs_rq's child load-average */ | |
2872 | static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, | |
2873 | struct sched_entity *se, | |
2874 | int wakeup) | |
2875 | { | |
2876 | /* | |
2877 | * We track migrations using entity decay_count <= 0, on a wake-up | |
2878 | * migration we use a negative decay count to track the remote decays | |
2879 | * accumulated while sleeping. | |
2880 | * | |
2881 | * Newly forked tasks are enqueued with se->avg.decay_count == 0, they | |
2882 | * are seen by enqueue_entity_load_avg() as a migration with an already | |
2883 | * constructed load_avg_contrib. | |
2884 | */ | |
2885 | if (unlikely(se->avg.decay_count <= 0)) { | |
2886 | se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq)); | |
2887 | if (se->avg.decay_count) { | |
2888 | /* | |
2889 | * In a wake-up migration we have to approximate the | |
2890 | * time sleeping. This is because we can't synchronize | |
2891 | * clock_task between the two cpus, and it is not | |
2892 | * guaranteed to be read-safe. Instead, we can | |
2893 | * approximate this using our carried decays, which are | |
2894 | * explicitly atomically readable. | |
2895 | */ | |
2896 | se->avg.last_runnable_update -= (-se->avg.decay_count) | |
2897 | << 20; | |
2898 | update_entity_load_avg(se, 0); | |
2899 | /* Indicate that we're now synchronized and on-rq */ | |
2900 | se->avg.decay_count = 0; | |
2901 | } | |
2902 | wakeup = 0; | |
2903 | } else { | |
2904 | __synchronize_entity_decay(se); | |
2905 | } | |
2906 | ||
2907 | /* migrated tasks did not contribute to our blocked load */ | |
2908 | if (wakeup) { | |
2909 | subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib); | |
2910 | update_entity_load_avg(se, 0); | |
2911 | } | |
2912 | ||
2913 | cfs_rq->runnable_load_avg += se->avg.load_avg_contrib; | |
2914 | cfs_rq->utilization_load_avg += se->avg.utilization_avg_contrib; | |
2915 | /* we force update consideration on load-balancer moves */ | |
2916 | update_cfs_rq_blocked_load(cfs_rq, !wakeup); | |
2917 | } | |
2918 | ||
2919 | /* | |
2920 | * Remove se's load from this cfs_rq child load-average, if the entity is | |
2921 | * transitioning to a blocked state we track its projected decay using | |
2922 | * blocked_load_avg. | |
2923 | */ | |
2924 | static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq, | |
2925 | struct sched_entity *se, | |
2926 | int sleep) | |
2927 | { | |
2928 | update_entity_load_avg(se, 1); | |
2929 | /* we force update consideration on load-balancer moves */ | |
2930 | update_cfs_rq_blocked_load(cfs_rq, !sleep); | |
2931 | ||
2932 | cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib; | |
2933 | cfs_rq->utilization_load_avg -= se->avg.utilization_avg_contrib; | |
2934 | if (sleep) { | |
2935 | cfs_rq->blocked_load_avg += se->avg.load_avg_contrib; | |
2936 | se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter); | |
2937 | } /* migrations, e.g. sleep=0 leave decay_count == 0 */ | |
2938 | } | |
2939 | ||
2940 | /* | |
2941 | * Update the rq's load with the elapsed running time before entering | |
2942 | * idle. if the last scheduled task is not a CFS task, idle_enter will | |
2943 | * be the only way to update the runnable statistic. | |
2944 | */ | |
2945 | void idle_enter_fair(struct rq *this_rq) | |
2946 | { | |
2947 | update_rq_runnable_avg(this_rq, 1); | |
2948 | } | |
2949 | ||
2950 | /* | |
2951 | * Update the rq's load with the elapsed idle time before a task is | |
2952 | * scheduled. if the newly scheduled task is not a CFS task, idle_exit will | |
2953 | * be the only way to update the runnable statistic. | |
2954 | */ | |
2955 | void idle_exit_fair(struct rq *this_rq) | |
2956 | { | |
2957 | update_rq_runnable_avg(this_rq, 0); | |
2958 | } | |
2959 | ||
2960 | static int idle_balance(struct rq *this_rq); | |
2961 | ||
2962 | #else /* CONFIG_SMP */ | |
2963 | ||
2964 | static inline void update_entity_load_avg(struct sched_entity *se, | |
2965 | int update_cfs_rq) {} | |
2966 | static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {} | |
2967 | static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, | |
2968 | struct sched_entity *se, | |
2969 | int wakeup) {} | |
2970 | static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq, | |
2971 | struct sched_entity *se, | |
2972 | int sleep) {} | |
2973 | static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, | |
2974 | int force_update) {} | |
2975 | ||
2976 | static inline int idle_balance(struct rq *rq) | |
2977 | { | |
2978 | return 0; | |
2979 | } | |
2980 | ||
2981 | #endif /* CONFIG_SMP */ | |
2982 | ||
2983 | static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
2984 | { | |
2985 | #ifdef CONFIG_SCHEDSTATS | |
2986 | struct task_struct *tsk = NULL; | |
2987 | ||
2988 | if (entity_is_task(se)) | |
2989 | tsk = task_of(se); | |
2990 | ||
2991 | if (se->statistics.sleep_start) { | |
2992 | u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start; | |
2993 | ||
2994 | if ((s64)delta < 0) | |
2995 | delta = 0; | |
2996 | ||
2997 | if (unlikely(delta > se->statistics.sleep_max)) | |
2998 | se->statistics.sleep_max = delta; | |
2999 | ||
3000 | se->statistics.sleep_start = 0; | |
3001 | se->statistics.sum_sleep_runtime += delta; | |
3002 | ||
3003 | if (tsk) { | |
3004 | account_scheduler_latency(tsk, delta >> 10, 1); | |
3005 | trace_sched_stat_sleep(tsk, delta); | |
3006 | } | |
3007 | } | |
3008 | if (se->statistics.block_start) { | |
3009 | u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start; | |
3010 | ||
3011 | if ((s64)delta < 0) | |
3012 | delta = 0; | |
3013 | ||
3014 | if (unlikely(delta > se->statistics.block_max)) | |
3015 | se->statistics.block_max = delta; | |
3016 | ||
3017 | se->statistics.block_start = 0; | |
3018 | se->statistics.sum_sleep_runtime += delta; | |
3019 | ||
3020 | if (tsk) { | |
3021 | if (tsk->in_iowait) { | |
3022 | se->statistics.iowait_sum += delta; | |
3023 | se->statistics.iowait_count++; | |
3024 | trace_sched_stat_iowait(tsk, delta); | |
3025 | } | |
3026 | ||
3027 | trace_sched_stat_blocked(tsk, delta); | |
3028 | ||
3029 | /* | |
3030 | * Blocking time is in units of nanosecs, so shift by | |
3031 | * 20 to get a milliseconds-range estimation of the | |
3032 | * amount of time that the task spent sleeping: | |
3033 | */ | |
3034 | if (unlikely(prof_on == SLEEP_PROFILING)) { | |
3035 | profile_hits(SLEEP_PROFILING, | |
3036 | (void *)get_wchan(tsk), | |
3037 | delta >> 20); | |
3038 | } | |
3039 | account_scheduler_latency(tsk, delta >> 10, 0); | |
3040 | } | |
3041 | } | |
3042 | #endif | |
3043 | } | |
3044 | ||
3045 | static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
3046 | { | |
3047 | #ifdef CONFIG_SCHED_DEBUG | |
3048 | s64 d = se->vruntime - cfs_rq->min_vruntime; | |
3049 | ||
3050 | if (d < 0) | |
3051 | d = -d; | |
3052 | ||
3053 | if (d > 3*sysctl_sched_latency) | |
3054 | schedstat_inc(cfs_rq, nr_spread_over); | |
3055 | #endif | |
3056 | } | |
3057 | ||
3058 | static void | |
3059 | place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) | |
3060 | { | |
3061 | u64 vruntime = cfs_rq->min_vruntime; | |
3062 | ||
3063 | /* | |
3064 | * The 'current' period is already promised to the current tasks, | |
3065 | * however the extra weight of the new task will slow them down a | |
3066 | * little, place the new task so that it fits in the slot that | |
3067 | * stays open at the end. | |
3068 | */ | |
3069 | if (initial && sched_feat(START_DEBIT)) | |
3070 | vruntime += sched_vslice(cfs_rq, se); | |
3071 | ||
3072 | /* sleeps up to a single latency don't count. */ | |
3073 | if (!initial) { | |
3074 | unsigned long thresh = sysctl_sched_latency; | |
3075 | ||
3076 | /* | |
3077 | * Halve their sleep time's effect, to allow | |
3078 | * for a gentler effect of sleepers: | |
3079 | */ | |
3080 | if (sched_feat(GENTLE_FAIR_SLEEPERS)) | |
3081 | thresh >>= 1; | |
3082 | ||
3083 | vruntime -= thresh; | |
3084 | } | |
3085 | ||
3086 | /* ensure we never gain time by being placed backwards. */ | |
3087 | se->vruntime = max_vruntime(se->vruntime, vruntime); | |
3088 | } | |
3089 | ||
3090 | static void check_enqueue_throttle(struct cfs_rq *cfs_rq); | |
3091 | ||
3092 | static void | |
3093 | enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) | |
3094 | { | |
3095 | /* | |
3096 | * Update the normalized vruntime before updating min_vruntime | |
3097 | * through calling update_curr(). | |
3098 | */ | |
3099 | if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING)) | |
3100 | se->vruntime += cfs_rq->min_vruntime; | |
3101 | ||
3102 | /* | |
3103 | * Update run-time statistics of the 'current'. | |
3104 | */ | |
3105 | update_curr(cfs_rq); | |
3106 | enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP); | |
3107 | account_entity_enqueue(cfs_rq, se); | |
3108 | update_cfs_shares(cfs_rq); | |
3109 | ||
3110 | if (flags & ENQUEUE_WAKEUP) { | |
3111 | place_entity(cfs_rq, se, 0); | |
3112 | enqueue_sleeper(cfs_rq, se); | |
3113 | } | |
3114 | ||
3115 | update_stats_enqueue(cfs_rq, se); | |
3116 | check_spread(cfs_rq, se); | |
3117 | if (se != cfs_rq->curr) | |
3118 | __enqueue_entity(cfs_rq, se); | |
3119 | se->on_rq = 1; | |
3120 | ||
3121 | if (cfs_rq->nr_running == 1) { | |
3122 | list_add_leaf_cfs_rq(cfs_rq); | |
3123 | check_enqueue_throttle(cfs_rq); | |
3124 | } | |
3125 | } | |
3126 | ||
3127 | static void __clear_buddies_last(struct sched_entity *se) | |
3128 | { | |
3129 | for_each_sched_entity(se) { | |
3130 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
3131 | if (cfs_rq->last != se) | |
3132 | break; | |
3133 | ||
3134 | cfs_rq->last = NULL; | |
3135 | } | |
3136 | } | |
3137 | ||
3138 | static void __clear_buddies_next(struct sched_entity *se) | |
3139 | { | |
3140 | for_each_sched_entity(se) { | |
3141 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
3142 | if (cfs_rq->next != se) | |
3143 | break; | |
3144 | ||
3145 | cfs_rq->next = NULL; | |
3146 | } | |
3147 | } | |
3148 | ||
3149 | static void __clear_buddies_skip(struct sched_entity *se) | |
3150 | { | |
3151 | for_each_sched_entity(se) { | |
3152 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
3153 | if (cfs_rq->skip != se) | |
3154 | break; | |
3155 | ||
3156 | cfs_rq->skip = NULL; | |
3157 | } | |
3158 | } | |
3159 | ||
3160 | static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
3161 | { | |
3162 | if (cfs_rq->last == se) | |
3163 | __clear_buddies_last(se); | |
3164 | ||
3165 | if (cfs_rq->next == se) | |
3166 | __clear_buddies_next(se); | |
3167 | ||
3168 | if (cfs_rq->skip == se) | |
3169 | __clear_buddies_skip(se); | |
3170 | } | |
3171 | ||
3172 | static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); | |
3173 | ||
3174 | static void | |
3175 | dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) | |
3176 | { | |
3177 | /* | |
3178 | * Update run-time statistics of the 'current'. | |
3179 | */ | |
3180 | update_curr(cfs_rq); | |
3181 | dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP); | |
3182 | ||
3183 | update_stats_dequeue(cfs_rq, se); | |
3184 | if (flags & DEQUEUE_SLEEP) { | |
3185 | #ifdef CONFIG_SCHEDSTATS | |
3186 | if (entity_is_task(se)) { | |
3187 | struct task_struct *tsk = task_of(se); | |
3188 | ||
3189 | if (tsk->state & TASK_INTERRUPTIBLE) | |
3190 | se->statistics.sleep_start = rq_clock(rq_of(cfs_rq)); | |
3191 | if (tsk->state & TASK_UNINTERRUPTIBLE) | |
3192 | se->statistics.block_start = rq_clock(rq_of(cfs_rq)); | |
3193 | } | |
3194 | #endif | |
3195 | } | |
3196 | ||
3197 | clear_buddies(cfs_rq, se); | |
3198 | ||
3199 | if (se != cfs_rq->curr) | |
3200 | __dequeue_entity(cfs_rq, se); | |
3201 | se->on_rq = 0; | |
3202 | account_entity_dequeue(cfs_rq, se); | |
3203 | ||
3204 | /* | |
3205 | * Normalize the entity after updating the min_vruntime because the | |
3206 | * update can refer to the ->curr item and we need to reflect this | |
3207 | * movement in our normalized position. | |
3208 | */ | |
3209 | if (!(flags & DEQUEUE_SLEEP)) | |
3210 | se->vruntime -= cfs_rq->min_vruntime; | |
3211 | ||
3212 | /* return excess runtime on last dequeue */ | |
3213 | return_cfs_rq_runtime(cfs_rq); | |
3214 | ||
3215 | update_min_vruntime(cfs_rq); | |
3216 | update_cfs_shares(cfs_rq); | |
3217 | } | |
3218 | ||
3219 | /* | |
3220 | * Preempt the current task with a newly woken task if needed: | |
3221 | */ | |
3222 | static void | |
3223 | check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) | |
3224 | { | |
3225 | unsigned long ideal_runtime, delta_exec; | |
3226 | struct sched_entity *se; | |
3227 | s64 delta; | |
3228 | ||
3229 | ideal_runtime = sched_slice(cfs_rq, curr); | |
3230 | delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; | |
3231 | if (delta_exec > ideal_runtime) { | |
3232 | resched_curr(rq_of(cfs_rq)); | |
3233 | /* | |
3234 | * The current task ran long enough, ensure it doesn't get | |
3235 | * re-elected due to buddy favours. | |
3236 | */ | |
3237 | clear_buddies(cfs_rq, curr); | |
3238 | return; | |
3239 | } | |
3240 | ||
3241 | /* | |
3242 | * Ensure that a task that missed wakeup preemption by a | |
3243 | * narrow margin doesn't have to wait for a full slice. | |
3244 | * This also mitigates buddy induced latencies under load. | |
3245 | */ | |
3246 | if (delta_exec < sysctl_sched_min_granularity) | |
3247 | return; | |
3248 | ||
3249 | se = __pick_first_entity(cfs_rq); | |
3250 | delta = curr->vruntime - se->vruntime; | |
3251 | ||
3252 | if (delta < 0) | |
3253 | return; | |
3254 | ||
3255 | if (delta > ideal_runtime) | |
3256 | resched_curr(rq_of(cfs_rq)); | |
3257 | } | |
3258 | ||
3259 | static void | |
3260 | set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) | |
3261 | { | |
3262 | /* 'current' is not kept within the tree. */ | |
3263 | if (se->on_rq) { | |
3264 | /* | |
3265 | * Any task has to be enqueued before it get to execute on | |
3266 | * a CPU. So account for the time it spent waiting on the | |
3267 | * runqueue. | |
3268 | */ | |
3269 | update_stats_wait_end(cfs_rq, se); | |
3270 | __dequeue_entity(cfs_rq, se); | |
3271 | update_entity_load_avg(se, 1); | |
3272 | } | |
3273 | ||
3274 | update_stats_curr_start(cfs_rq, se); | |
3275 | cfs_rq->curr = se; | |
3276 | #ifdef CONFIG_SCHEDSTATS | |
3277 | /* | |
3278 | * Track our maximum slice length, if the CPU's load is at | |
3279 | * least twice that of our own weight (i.e. dont track it | |
3280 | * when there are only lesser-weight tasks around): | |
3281 | */ | |
3282 | if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) { | |
3283 | se->statistics.slice_max = max(se->statistics.slice_max, | |
3284 | se->sum_exec_runtime - se->prev_sum_exec_runtime); | |
3285 | } | |
3286 | #endif | |
3287 | se->prev_sum_exec_runtime = se->sum_exec_runtime; | |
3288 | } | |
3289 | ||
3290 | static int | |
3291 | wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); | |
3292 | ||
3293 | /* | |
3294 | * Pick the next process, keeping these things in mind, in this order: | |
3295 | * 1) keep things fair between processes/task groups | |
3296 | * 2) pick the "next" process, since someone really wants that to run | |
3297 | * 3) pick the "last" process, for cache locality | |
3298 | * 4) do not run the "skip" process, if something else is available | |
3299 | */ | |
3300 | static struct sched_entity * | |
3301 | pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) | |
3302 | { | |
3303 | struct sched_entity *left = __pick_first_entity(cfs_rq); | |
3304 | struct sched_entity *se; | |
3305 | ||
3306 | /* | |
3307 | * If curr is set we have to see if its left of the leftmost entity | |
3308 | * still in the tree, provided there was anything in the tree at all. | |
3309 | */ | |
3310 | if (!left || (curr && entity_before(curr, left))) | |
3311 | left = curr; | |
3312 | ||
3313 | se = left; /* ideally we run the leftmost entity */ | |
3314 | ||
3315 | /* | |
3316 | * Avoid running the skip buddy, if running something else can | |
3317 | * be done without getting too unfair. | |
3318 | */ | |
3319 | if (cfs_rq->skip == se) { | |
3320 | struct sched_entity *second; | |
3321 | ||
3322 | if (se == curr) { | |
3323 | second = __pick_first_entity(cfs_rq); | |
3324 | } else { | |
3325 | second = __pick_next_entity(se); | |
3326 | if (!second || (curr && entity_before(curr, second))) | |
3327 | second = curr; | |
3328 | } | |
3329 | ||
3330 | if (second && wakeup_preempt_entity(second, left) < 1) | |
3331 | se = second; | |
3332 | } | |
3333 | ||
3334 | /* | |
3335 | * Prefer last buddy, try to return the CPU to a preempted task. | |
3336 | */ | |
3337 | if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) | |
3338 | se = cfs_rq->last; | |
3339 | ||
3340 | /* | |
3341 | * Someone really wants this to run. If it's not unfair, run it. | |
3342 | */ | |
3343 | if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) | |
3344 | se = cfs_rq->next; | |
3345 | ||
3346 | clear_buddies(cfs_rq, se); | |
3347 | ||
3348 | return se; | |
3349 | } | |
3350 | ||
3351 | static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq); | |
3352 | ||
3353 | static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) | |
3354 | { | |
3355 | /* | |
3356 | * If still on the runqueue then deactivate_task() | |
3357 | * was not called and update_curr() has to be done: | |
3358 | */ | |
3359 | if (prev->on_rq) | |
3360 | update_curr(cfs_rq); | |
3361 | ||
3362 | /* throttle cfs_rqs exceeding runtime */ | |
3363 | check_cfs_rq_runtime(cfs_rq); | |
3364 | ||
3365 | check_spread(cfs_rq, prev); | |
3366 | if (prev->on_rq) { | |
3367 | update_stats_wait_start(cfs_rq, prev); | |
3368 | /* Put 'current' back into the tree. */ | |
3369 | __enqueue_entity(cfs_rq, prev); | |
3370 | /* in !on_rq case, update occurred at dequeue */ | |
3371 | update_entity_load_avg(prev, 1); | |
3372 | } | |
3373 | cfs_rq->curr = NULL; | |
3374 | } | |
3375 | ||
3376 | static void | |
3377 | entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) | |
3378 | { | |
3379 | /* | |
3380 | * Update run-time statistics of the 'current'. | |
3381 | */ | |
3382 | update_curr(cfs_rq); | |
3383 | ||
3384 | /* | |
3385 | * Ensure that runnable average is periodically updated. | |
3386 | */ | |
3387 | update_entity_load_avg(curr, 1); | |
3388 | update_cfs_rq_blocked_load(cfs_rq, 1); | |
3389 | update_cfs_shares(cfs_rq); | |
3390 | ||
3391 | #ifdef CONFIG_SCHED_HRTICK | |
3392 | /* | |
3393 | * queued ticks are scheduled to match the slice, so don't bother | |
3394 | * validating it and just reschedule. | |
3395 | */ | |
3396 | if (queued) { | |
3397 | resched_curr(rq_of(cfs_rq)); | |
3398 | return; | |
3399 | } | |
3400 | /* | |
3401 | * don't let the period tick interfere with the hrtick preemption | |
3402 | */ | |
3403 | if (!sched_feat(DOUBLE_TICK) && | |
3404 | hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) | |
3405 | return; | |
3406 | #endif | |
3407 | ||
3408 | if (cfs_rq->nr_running > 1) | |
3409 | check_preempt_tick(cfs_rq, curr); | |
3410 | } | |
3411 | ||
3412 | ||
3413 | /************************************************** | |
3414 | * CFS bandwidth control machinery | |
3415 | */ | |
3416 | ||
3417 | #ifdef CONFIG_CFS_BANDWIDTH | |
3418 | ||
3419 | #ifdef HAVE_JUMP_LABEL | |
3420 | static struct static_key __cfs_bandwidth_used; | |
3421 | ||
3422 | static inline bool cfs_bandwidth_used(void) | |
3423 | { | |
3424 | return static_key_false(&__cfs_bandwidth_used); | |
3425 | } | |
3426 | ||
3427 | void cfs_bandwidth_usage_inc(void) | |
3428 | { | |
3429 | static_key_slow_inc(&__cfs_bandwidth_used); | |
3430 | } | |
3431 | ||
3432 | void cfs_bandwidth_usage_dec(void) | |
3433 | { | |
3434 | static_key_slow_dec(&__cfs_bandwidth_used); | |
3435 | } | |
3436 | #else /* HAVE_JUMP_LABEL */ | |
3437 | static bool cfs_bandwidth_used(void) | |
3438 | { | |
3439 | return true; | |
3440 | } | |
3441 | ||
3442 | void cfs_bandwidth_usage_inc(void) {} | |
3443 | void cfs_bandwidth_usage_dec(void) {} | |
3444 | #endif /* HAVE_JUMP_LABEL */ | |
3445 | ||
3446 | /* | |
3447 | * default period for cfs group bandwidth. | |
3448 | * default: 0.1s, units: nanoseconds | |
3449 | */ | |
3450 | static inline u64 default_cfs_period(void) | |
3451 | { | |
3452 | return 100000000ULL; | |
3453 | } | |
3454 | ||
3455 | static inline u64 sched_cfs_bandwidth_slice(void) | |
3456 | { | |
3457 | return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; | |
3458 | } | |
3459 | ||
3460 | /* | |
3461 | * Replenish runtime according to assigned quota and update expiration time. | |
3462 | * We use sched_clock_cpu directly instead of rq->clock to avoid adding | |
3463 | * additional synchronization around rq->lock. | |
3464 | * | |
3465 | * requires cfs_b->lock | |
3466 | */ | |
3467 | void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) | |
3468 | { | |
3469 | u64 now; | |
3470 | ||
3471 | if (cfs_b->quota == RUNTIME_INF) | |
3472 | return; | |
3473 | ||
3474 | now = sched_clock_cpu(smp_processor_id()); | |
3475 | cfs_b->runtime = cfs_b->quota; | |
3476 | cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); | |
3477 | } | |
3478 | ||
3479 | static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) | |
3480 | { | |
3481 | return &tg->cfs_bandwidth; | |
3482 | } | |
3483 | ||
3484 | /* rq->task_clock normalized against any time this cfs_rq has spent throttled */ | |
3485 | static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) | |
3486 | { | |
3487 | if (unlikely(cfs_rq->throttle_count)) | |
3488 | return cfs_rq->throttled_clock_task; | |
3489 | ||
3490 | return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time; | |
3491 | } | |
3492 | ||
3493 | /* returns 0 on failure to allocate runtime */ | |
3494 | static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) | |
3495 | { | |
3496 | struct task_group *tg = cfs_rq->tg; | |
3497 | struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); | |
3498 | u64 amount = 0, min_amount, expires; | |
3499 | ||
3500 | /* note: this is a positive sum as runtime_remaining <= 0 */ | |
3501 | min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; | |
3502 | ||
3503 | raw_spin_lock(&cfs_b->lock); | |
3504 | if (cfs_b->quota == RUNTIME_INF) | |
3505 | amount = min_amount; | |
3506 | else { | |
3507 | start_cfs_bandwidth(cfs_b); | |
3508 | ||
3509 | if (cfs_b->runtime > 0) { | |
3510 | amount = min(cfs_b->runtime, min_amount); | |
3511 | cfs_b->runtime -= amount; | |
3512 | cfs_b->idle = 0; | |
3513 | } | |
3514 | } | |
3515 | expires = cfs_b->runtime_expires; | |
3516 | raw_spin_unlock(&cfs_b->lock); | |
3517 | ||
3518 | cfs_rq->runtime_remaining += amount; | |
3519 | /* | |
3520 | * we may have advanced our local expiration to account for allowed | |
3521 | * spread between our sched_clock and the one on which runtime was | |
3522 | * issued. | |
3523 | */ | |
3524 | if ((s64)(expires - cfs_rq->runtime_expires) > 0) | |
3525 | cfs_rq->runtime_expires = expires; | |
3526 | ||
3527 | return cfs_rq->runtime_remaining > 0; | |
3528 | } | |
3529 | ||
3530 | /* | |
3531 | * Note: This depends on the synchronization provided by sched_clock and the | |
3532 | * fact that rq->clock snapshots this value. | |
3533 | */ | |
3534 | static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq) | |
3535 | { | |
3536 | struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); | |
3537 | ||
3538 | /* if the deadline is ahead of our clock, nothing to do */ | |
3539 | if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0)) | |
3540 | return; | |
3541 | ||
3542 | if (cfs_rq->runtime_remaining < 0) | |
3543 | return; | |
3544 | ||
3545 | /* | |
3546 | * If the local deadline has passed we have to consider the | |
3547 | * possibility that our sched_clock is 'fast' and the global deadline | |
3548 | * has not truly expired. | |
3549 | * | |
3550 | * Fortunately we can check determine whether this the case by checking | |
3551 | * whether the global deadline has advanced. It is valid to compare | |
3552 | * cfs_b->runtime_expires without any locks since we only care about | |
3553 | * exact equality, so a partial write will still work. | |
3554 | */ | |
3555 | ||
3556 | if (cfs_rq->runtime_expires != cfs_b->runtime_expires) { | |
3557 | /* extend local deadline, drift is bounded above by 2 ticks */ | |
3558 | cfs_rq->runtime_expires += TICK_NSEC; | |
3559 | } else { | |
3560 | /* global deadline is ahead, expiration has passed */ | |
3561 | cfs_rq->runtime_remaining = 0; | |
3562 | } | |
3563 | } | |
3564 | ||
3565 | static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) | |
3566 | { | |
3567 | /* dock delta_exec before expiring quota (as it could span periods) */ | |
3568 | cfs_rq->runtime_remaining -= delta_exec; | |
3569 | expire_cfs_rq_runtime(cfs_rq); | |
3570 | ||
3571 | if (likely(cfs_rq->runtime_remaining > 0)) | |
3572 | return; | |
3573 | ||
3574 | /* | |
3575 | * if we're unable to extend our runtime we resched so that the active | |
3576 | * hierarchy can be throttled | |
3577 | */ | |
3578 | if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) | |
3579 | resched_curr(rq_of(cfs_rq)); | |
3580 | } | |
3581 | ||
3582 | static __always_inline | |
3583 | void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) | |
3584 | { | |
3585 | if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) | |
3586 | return; | |
3587 | ||
3588 | __account_cfs_rq_runtime(cfs_rq, delta_exec); | |
3589 | } | |
3590 | ||
3591 | static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) | |
3592 | { | |
3593 | return cfs_bandwidth_used() && cfs_rq->throttled; | |
3594 | } | |
3595 | ||
3596 | /* check whether cfs_rq, or any parent, is throttled */ | |
3597 | static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) | |
3598 | { | |
3599 | return cfs_bandwidth_used() && cfs_rq->throttle_count; | |
3600 | } | |
3601 | ||
3602 | /* | |
3603 | * Ensure that neither of the group entities corresponding to src_cpu or | |
3604 | * dest_cpu are members of a throttled hierarchy when performing group | |
3605 | * load-balance operations. | |
3606 | */ | |
3607 | static inline int throttled_lb_pair(struct task_group *tg, | |
3608 | int src_cpu, int dest_cpu) | |
3609 | { | |
3610 | struct cfs_rq *src_cfs_rq, *dest_cfs_rq; | |
3611 | ||
3612 | src_cfs_rq = tg->cfs_rq[src_cpu]; | |
3613 | dest_cfs_rq = tg->cfs_rq[dest_cpu]; | |
3614 | ||
3615 | return throttled_hierarchy(src_cfs_rq) || | |
3616 | throttled_hierarchy(dest_cfs_rq); | |
3617 | } | |
3618 | ||
3619 | /* updated child weight may affect parent so we have to do this bottom up */ | |
3620 | static int tg_unthrottle_up(struct task_group *tg, void *data) | |
3621 | { | |
3622 | struct rq *rq = data; | |
3623 | struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; | |
3624 | ||
3625 | cfs_rq->throttle_count--; | |
3626 | #ifdef CONFIG_SMP | |
3627 | if (!cfs_rq->throttle_count) { | |
3628 | /* adjust cfs_rq_clock_task() */ | |
3629 | cfs_rq->throttled_clock_task_time += rq_clock_task(rq) - | |
3630 | cfs_rq->throttled_clock_task; | |
3631 | } | |
3632 | #endif | |
3633 | ||
3634 | return 0; | |
3635 | } | |
3636 | ||
3637 | static int tg_throttle_down(struct task_group *tg, void *data) | |
3638 | { | |
3639 | struct rq *rq = data; | |
3640 | struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; | |
3641 | ||
3642 | /* group is entering throttled state, stop time */ | |
3643 | if (!cfs_rq->throttle_count) | |
3644 | cfs_rq->throttled_clock_task = rq_clock_task(rq); | |
3645 | cfs_rq->throttle_count++; | |
3646 | ||
3647 | return 0; | |
3648 | } | |
3649 | ||
3650 | static void throttle_cfs_rq(struct cfs_rq *cfs_rq) | |
3651 | { | |
3652 | struct rq *rq = rq_of(cfs_rq); | |
3653 | struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); | |
3654 | struct sched_entity *se; | |
3655 | long task_delta, dequeue = 1; | |
3656 | bool empty; | |
3657 | ||
3658 | se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; | |
3659 | ||
3660 | /* freeze hierarchy runnable averages while throttled */ | |
3661 | rcu_read_lock(); | |
3662 | walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); | |
3663 | rcu_read_unlock(); | |
3664 | ||
3665 | task_delta = cfs_rq->h_nr_running; | |
3666 | for_each_sched_entity(se) { | |
3667 | struct cfs_rq *qcfs_rq = cfs_rq_of(se); | |
3668 | /* throttled entity or throttle-on-deactivate */ | |
3669 | if (!se->on_rq) | |
3670 | break; | |
3671 | ||
3672 | if (dequeue) | |
3673 | dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); | |
3674 | qcfs_rq->h_nr_running -= task_delta; | |
3675 | ||
3676 | if (qcfs_rq->load.weight) | |
3677 | dequeue = 0; | |
3678 | } | |
3679 | ||
3680 | if (!se) | |
3681 | sub_nr_running(rq, task_delta); | |
3682 | ||
3683 | cfs_rq->throttled = 1; | |
3684 | cfs_rq->throttled_clock = rq_clock(rq); | |
3685 | raw_spin_lock(&cfs_b->lock); | |
3686 | empty = list_empty(&cfs_rq->throttled_list); | |
3687 | ||
3688 | /* | |
3689 | * Add to the _head_ of the list, so that an already-started | |
3690 | * distribute_cfs_runtime will not see us | |
3691 | */ | |
3692 | list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); | |
3693 | ||
3694 | /* | |
3695 | * If we're the first throttled task, make sure the bandwidth | |
3696 | * timer is running. | |
3697 | */ | |
3698 | if (empty) | |
3699 | start_cfs_bandwidth(cfs_b); | |
3700 | ||
3701 | raw_spin_unlock(&cfs_b->lock); | |
3702 | } | |
3703 | ||
3704 | void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) | |
3705 | { | |
3706 | struct rq *rq = rq_of(cfs_rq); | |
3707 | struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); | |
3708 | struct sched_entity *se; | |
3709 | int enqueue = 1; | |
3710 | long task_delta; | |
3711 | ||
3712 | se = cfs_rq->tg->se[cpu_of(rq)]; | |
3713 | ||
3714 | cfs_rq->throttled = 0; | |
3715 | ||
3716 | update_rq_clock(rq); | |
3717 | ||
3718 | raw_spin_lock(&cfs_b->lock); | |
3719 | cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock; | |
3720 | list_del_rcu(&cfs_rq->throttled_list); | |
3721 | raw_spin_unlock(&cfs_b->lock); | |
3722 | ||
3723 | /* update hierarchical throttle state */ | |
3724 | walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); | |
3725 | ||
3726 | if (!cfs_rq->load.weight) | |
3727 | return; | |
3728 | ||
3729 | task_delta = cfs_rq->h_nr_running; | |
3730 | for_each_sched_entity(se) { | |
3731 | if (se->on_rq) | |
3732 | enqueue = 0; | |
3733 | ||
3734 | cfs_rq = cfs_rq_of(se); | |
3735 | if (enqueue) | |
3736 | enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); | |
3737 | cfs_rq->h_nr_running += task_delta; | |
3738 | ||
3739 | if (cfs_rq_throttled(cfs_rq)) | |
3740 | break; | |
3741 | } | |
3742 | ||
3743 | if (!se) | |
3744 | add_nr_running(rq, task_delta); | |
3745 | ||
3746 | /* determine whether we need to wake up potentially idle cpu */ | |
3747 | if (rq->curr == rq->idle && rq->cfs.nr_running) | |
3748 | resched_curr(rq); | |
3749 | } | |
3750 | ||
3751 | static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, | |
3752 | u64 remaining, u64 expires) | |
3753 | { | |
3754 | struct cfs_rq *cfs_rq; | |
3755 | u64 runtime; | |
3756 | u64 starting_runtime = remaining; | |
3757 | ||
3758 | rcu_read_lock(); | |
3759 | list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, | |
3760 | throttled_list) { | |
3761 | struct rq *rq = rq_of(cfs_rq); | |
3762 | ||
3763 | raw_spin_lock(&rq->lock); | |
3764 | if (!cfs_rq_throttled(cfs_rq)) | |
3765 | goto next; | |
3766 | ||
3767 | runtime = -cfs_rq->runtime_remaining + 1; | |
3768 | if (runtime > remaining) | |
3769 | runtime = remaining; | |
3770 | remaining -= runtime; | |
3771 | ||
3772 | cfs_rq->runtime_remaining += runtime; | |
3773 | cfs_rq->runtime_expires = expires; | |
3774 | ||
3775 | /* we check whether we're throttled above */ | |
3776 | if (cfs_rq->runtime_remaining > 0) | |
3777 | unthrottle_cfs_rq(cfs_rq); | |
3778 | ||
3779 | next: | |
3780 | raw_spin_unlock(&rq->lock); | |
3781 | ||
3782 | if (!remaining) | |
3783 | break; | |
3784 | } | |
3785 | rcu_read_unlock(); | |
3786 | ||
3787 | return starting_runtime - remaining; | |
3788 | } | |
3789 | ||
3790 | /* | |
3791 | * Responsible for refilling a task_group's bandwidth and unthrottling its | |
3792 | * cfs_rqs as appropriate. If there has been no activity within the last | |
3793 | * period the timer is deactivated until scheduling resumes; cfs_b->idle is | |
3794 | * used to track this state. | |
3795 | */ | |
3796 | static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) | |
3797 | { | |
3798 | u64 runtime, runtime_expires; | |
3799 | int throttled; | |
3800 | ||
3801 | /* no need to continue the timer with no bandwidth constraint */ | |
3802 | if (cfs_b->quota == RUNTIME_INF) | |
3803 | goto out_deactivate; | |
3804 | ||
3805 | throttled = !list_empty(&cfs_b->throttled_cfs_rq); | |
3806 | cfs_b->nr_periods += overrun; | |
3807 | ||
3808 | /* | |
3809 | * idle depends on !throttled (for the case of a large deficit), and if | |
3810 | * we're going inactive then everything else can be deferred | |
3811 | */ | |
3812 | if (cfs_b->idle && !throttled) | |
3813 | goto out_deactivate; | |
3814 | ||
3815 | __refill_cfs_bandwidth_runtime(cfs_b); | |
3816 | ||
3817 | if (!throttled) { | |
3818 | /* mark as potentially idle for the upcoming period */ | |
3819 | cfs_b->idle = 1; | |
3820 | return 0; | |
3821 | } | |
3822 | ||
3823 | /* account preceding periods in which throttling occurred */ | |
3824 | cfs_b->nr_throttled += overrun; | |
3825 | ||
3826 | runtime_expires = cfs_b->runtime_expires; | |
3827 | ||
3828 | /* | |
3829 | * This check is repeated as we are holding onto the new bandwidth while | |
3830 | * we unthrottle. This can potentially race with an unthrottled group | |
3831 | * trying to acquire new bandwidth from the global pool. This can result | |
3832 | * in us over-using our runtime if it is all used during this loop, but | |
3833 | * only by limited amounts in that extreme case. | |
3834 | */ | |
3835 | while (throttled && cfs_b->runtime > 0) { | |
3836 | runtime = cfs_b->runtime; | |
3837 | raw_spin_unlock(&cfs_b->lock); | |
3838 | /* we can't nest cfs_b->lock while distributing bandwidth */ | |
3839 | runtime = distribute_cfs_runtime(cfs_b, runtime, | |
3840 | runtime_expires); | |
3841 | raw_spin_lock(&cfs_b->lock); | |
3842 | ||
3843 | throttled = !list_empty(&cfs_b->throttled_cfs_rq); | |
3844 | ||
3845 | cfs_b->runtime -= min(runtime, cfs_b->runtime); | |
3846 | } | |
3847 | ||
3848 | /* | |
3849 | * While we are ensured activity in the period following an | |
3850 | * unthrottle, this also covers the case in which the new bandwidth is | |
3851 | * insufficient to cover the existing bandwidth deficit. (Forcing the | |
3852 | * timer to remain active while there are any throttled entities.) | |
3853 | */ | |
3854 | cfs_b->idle = 0; | |
3855 | ||
3856 | return 0; | |
3857 | ||
3858 | out_deactivate: | |
3859 | return 1; | |
3860 | } | |
3861 | ||
3862 | /* a cfs_rq won't donate quota below this amount */ | |
3863 | static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; | |
3864 | /* minimum remaining period time to redistribute slack quota */ | |
3865 | static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; | |
3866 | /* how long we wait to gather additional slack before distributing */ | |
3867 | static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; | |
3868 | ||
3869 | /* | |
3870 | * Are we near the end of the current quota period? | |
3871 | * | |
3872 | * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the | |
3873 | * hrtimer base being cleared by hrtimer_start. In the case of | |
3874 | * migrate_hrtimers, base is never cleared, so we are fine. | |
3875 | */ | |
3876 | static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) | |
3877 | { | |
3878 | struct hrtimer *refresh_timer = &cfs_b->period_timer; | |
3879 | u64 remaining; | |
3880 | ||
3881 | /* if the call-back is running a quota refresh is already occurring */ | |
3882 | if (hrtimer_callback_running(refresh_timer)) | |
3883 | return 1; | |
3884 | ||
3885 | /* is a quota refresh about to occur? */ | |
3886 | remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); | |
3887 | if (remaining < min_expire) | |
3888 | return 1; | |
3889 | ||
3890 | return 0; | |
3891 | } | |
3892 | ||
3893 | static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) | |
3894 | { | |
3895 | u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; | |
3896 | ||
3897 | /* if there's a quota refresh soon don't bother with slack */ | |
3898 | if (runtime_refresh_within(cfs_b, min_left)) | |
3899 | return; | |
3900 | ||
3901 | hrtimer_start(&cfs_b->slack_timer, | |
3902 | ns_to_ktime(cfs_bandwidth_slack_period), | |
3903 | HRTIMER_MODE_REL); | |
3904 | } | |
3905 | ||
3906 | /* we know any runtime found here is valid as update_curr() precedes return */ | |
3907 | static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) | |
3908 | { | |
3909 | struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); | |
3910 | s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; | |
3911 | ||
3912 | if (slack_runtime <= 0) | |
3913 | return; | |
3914 | ||
3915 | raw_spin_lock(&cfs_b->lock); | |
3916 | if (cfs_b->quota != RUNTIME_INF && | |
3917 | cfs_rq->runtime_expires == cfs_b->runtime_expires) { | |
3918 | cfs_b->runtime += slack_runtime; | |
3919 | ||
3920 | /* we are under rq->lock, defer unthrottling using a timer */ | |
3921 | if (cfs_b->runtime > sched_cfs_bandwidth_slice() && | |
3922 | !list_empty(&cfs_b->throttled_cfs_rq)) | |
3923 | start_cfs_slack_bandwidth(cfs_b); | |
3924 | } | |
3925 | raw_spin_unlock(&cfs_b->lock); | |
3926 | ||
3927 | /* even if it's not valid for return we don't want to try again */ | |
3928 | cfs_rq->runtime_remaining -= slack_runtime; | |
3929 | } | |
3930 | ||
3931 | static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) | |
3932 | { | |
3933 | if (!cfs_bandwidth_used()) | |
3934 | return; | |
3935 | ||
3936 | if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) | |
3937 | return; | |
3938 | ||
3939 | __return_cfs_rq_runtime(cfs_rq); | |
3940 | } | |
3941 | ||
3942 | /* | |
3943 | * This is done with a timer (instead of inline with bandwidth return) since | |
3944 | * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. | |
3945 | */ | |
3946 | static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) | |
3947 | { | |
3948 | u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); | |
3949 | u64 expires; | |
3950 | ||
3951 | /* confirm we're still not at a refresh boundary */ | |
3952 | raw_spin_lock(&cfs_b->lock); | |
3953 | if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { | |
3954 | raw_spin_unlock(&cfs_b->lock); | |
3955 | return; | |
3956 | } | |
3957 | ||
3958 | if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) | |
3959 | runtime = cfs_b->runtime; | |
3960 | ||
3961 | expires = cfs_b->runtime_expires; | |
3962 | raw_spin_unlock(&cfs_b->lock); | |
3963 | ||
3964 | if (!runtime) | |
3965 | return; | |
3966 | ||
3967 | runtime = distribute_cfs_runtime(cfs_b, runtime, expires); | |
3968 | ||
3969 | raw_spin_lock(&cfs_b->lock); | |
3970 | if (expires == cfs_b->runtime_expires) | |
3971 | cfs_b->runtime -= min(runtime, cfs_b->runtime); | |
3972 | raw_spin_unlock(&cfs_b->lock); | |
3973 | } | |
3974 | ||
3975 | /* | |
3976 | * When a group wakes up we want to make sure that its quota is not already | |
3977 | * expired/exceeded, otherwise it may be allowed to steal additional ticks of | |
3978 | * runtime as update_curr() throttling can not not trigger until it's on-rq. | |
3979 | */ | |
3980 | static void check_enqueue_throttle(struct cfs_rq *cfs_rq) | |
3981 | { | |
3982 | if (!cfs_bandwidth_used()) | |
3983 | return; | |
3984 | ||
3985 | /* an active group must be handled by the update_curr()->put() path */ | |
3986 | if (!cfs_rq->runtime_enabled || cfs_rq->curr) | |
3987 | return; | |
3988 | ||
3989 | /* ensure the group is not already throttled */ | |
3990 | if (cfs_rq_throttled(cfs_rq)) | |
3991 | return; | |
3992 | ||
3993 | /* update runtime allocation */ | |
3994 | account_cfs_rq_runtime(cfs_rq, 0); | |
3995 | if (cfs_rq->runtime_remaining <= 0) | |
3996 | throttle_cfs_rq(cfs_rq); | |
3997 | } | |
3998 | ||
3999 | /* conditionally throttle active cfs_rq's from put_prev_entity() */ | |
4000 | static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) | |
4001 | { | |
4002 | if (!cfs_bandwidth_used()) | |
4003 | return false; | |
4004 | ||
4005 | if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) | |
4006 | return false; | |
4007 | ||
4008 | /* | |
4009 | * it's possible for a throttled entity to be forced into a running | |
4010 | * state (e.g. set_curr_task), in this case we're finished. | |
4011 | */ | |
4012 | if (cfs_rq_throttled(cfs_rq)) | |
4013 | return true; | |
4014 | ||
4015 | throttle_cfs_rq(cfs_rq); | |
4016 | return true; | |
4017 | } | |
4018 | ||
4019 | static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) | |
4020 | { | |
4021 | struct cfs_bandwidth *cfs_b = | |
4022 | container_of(timer, struct cfs_bandwidth, slack_timer); | |
4023 | ||
4024 | do_sched_cfs_slack_timer(cfs_b); | |
4025 | ||
4026 | return HRTIMER_NORESTART; | |
4027 | } | |
4028 | ||
4029 | static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) | |
4030 | { | |
4031 | struct cfs_bandwidth *cfs_b = | |
4032 | container_of(timer, struct cfs_bandwidth, period_timer); | |
4033 | int overrun; | |
4034 | int idle = 0; | |
4035 | ||
4036 | raw_spin_lock(&cfs_b->lock); | |
4037 | for (;;) { | |
4038 | overrun = hrtimer_forward_now(timer, cfs_b->period); | |
4039 | if (!overrun) | |
4040 | break; | |
4041 | ||
4042 | idle = do_sched_cfs_period_timer(cfs_b, overrun); | |
4043 | } | |
4044 | if (idle) | |
4045 | cfs_b->period_active = 0; | |
4046 | raw_spin_unlock(&cfs_b->lock); | |
4047 | ||
4048 | return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; | |
4049 | } | |
4050 | ||
4051 | void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) | |
4052 | { | |
4053 | raw_spin_lock_init(&cfs_b->lock); | |
4054 | cfs_b->runtime = 0; | |
4055 | cfs_b->quota = RUNTIME_INF; | |
4056 | cfs_b->period = ns_to_ktime(default_cfs_period()); | |
4057 | ||
4058 | INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); | |
4059 | hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED); | |
4060 | cfs_b->period_timer.function = sched_cfs_period_timer; | |
4061 | hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
4062 | cfs_b->slack_timer.function = sched_cfs_slack_timer; | |
4063 | } | |
4064 | ||
4065 | static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) | |
4066 | { | |
4067 | cfs_rq->runtime_enabled = 0; | |
4068 | INIT_LIST_HEAD(&cfs_rq->throttled_list); | |
4069 | } | |
4070 | ||
4071 | void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) | |
4072 | { | |
4073 | lockdep_assert_held(&cfs_b->lock); | |
4074 | ||
4075 | if (!cfs_b->period_active) { | |
4076 | cfs_b->period_active = 1; | |
4077 | hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); | |
4078 | hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); | |
4079 | } | |
4080 | } | |
4081 | ||
4082 | static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) | |
4083 | { | |
4084 | /* init_cfs_bandwidth() was not called */ | |
4085 | if (!cfs_b->throttled_cfs_rq.next) | |
4086 | return; | |
4087 | ||
4088 | hrtimer_cancel(&cfs_b->period_timer); | |
4089 | hrtimer_cancel(&cfs_b->slack_timer); | |
4090 | } | |
4091 | ||
4092 | static void __maybe_unused update_runtime_enabled(struct rq *rq) | |
4093 | { | |
4094 | struct cfs_rq *cfs_rq; | |
4095 | ||
4096 | for_each_leaf_cfs_rq(rq, cfs_rq) { | |
4097 | struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth; | |
4098 | ||
4099 | raw_spin_lock(&cfs_b->lock); | |
4100 | cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF; | |
4101 | raw_spin_unlock(&cfs_b->lock); | |
4102 | } | |
4103 | } | |
4104 | ||
4105 | static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) | |
4106 | { | |
4107 | struct cfs_rq *cfs_rq; | |
4108 | ||
4109 | for_each_leaf_cfs_rq(rq, cfs_rq) { | |
4110 | if (!cfs_rq->runtime_enabled) | |
4111 | continue; | |
4112 | ||
4113 | /* | |
4114 | * clock_task is not advancing so we just need to make sure | |
4115 | * there's some valid quota amount | |
4116 | */ | |
4117 | cfs_rq->runtime_remaining = 1; | |
4118 | /* | |
4119 | * Offline rq is schedulable till cpu is completely disabled | |
4120 | * in take_cpu_down(), so we prevent new cfs throttling here. | |
4121 | */ | |
4122 | cfs_rq->runtime_enabled = 0; | |
4123 | ||
4124 | if (cfs_rq_throttled(cfs_rq)) | |
4125 | unthrottle_cfs_rq(cfs_rq); | |
4126 | } | |
4127 | } | |
4128 | ||
4129 | #else /* CONFIG_CFS_BANDWIDTH */ | |
4130 | static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) | |
4131 | { | |
4132 | return rq_clock_task(rq_of(cfs_rq)); | |
4133 | } | |
4134 | ||
4135 | static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {} | |
4136 | static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; } | |
4137 | static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} | |
4138 | static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} | |
4139 | ||
4140 | static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) | |
4141 | { | |
4142 | return 0; | |
4143 | } | |
4144 | ||
4145 | static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) | |
4146 | { | |
4147 | return 0; | |
4148 | } | |
4149 | ||
4150 | static inline int throttled_lb_pair(struct task_group *tg, | |
4151 | int src_cpu, int dest_cpu) | |
4152 | { | |
4153 | return 0; | |
4154 | } | |
4155 | ||
4156 | void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} | |
4157 | ||
4158 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
4159 | static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} | |
4160 | #endif | |
4161 | ||
4162 | static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) | |
4163 | { | |
4164 | return NULL; | |
4165 | } | |
4166 | static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} | |
4167 | static inline void update_runtime_enabled(struct rq *rq) {} | |
4168 | static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} | |
4169 | ||
4170 | #endif /* CONFIG_CFS_BANDWIDTH */ | |
4171 | ||
4172 | /************************************************** | |
4173 | * CFS operations on tasks: | |
4174 | */ | |
4175 | ||
4176 | #ifdef CONFIG_SCHED_HRTICK | |
4177 | static void hrtick_start_fair(struct rq *rq, struct task_struct *p) | |
4178 | { | |
4179 | struct sched_entity *se = &p->se; | |
4180 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
4181 | ||
4182 | WARN_ON(task_rq(p) != rq); | |
4183 | ||
4184 | if (cfs_rq->nr_running > 1) { | |
4185 | u64 slice = sched_slice(cfs_rq, se); | |
4186 | u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; | |
4187 | s64 delta = slice - ran; | |
4188 | ||
4189 | if (delta < 0) { | |
4190 | if (rq->curr == p) | |
4191 | resched_curr(rq); | |
4192 | return; | |
4193 | } | |
4194 | hrtick_start(rq, delta); | |
4195 | } | |
4196 | } | |
4197 | ||
4198 | /* | |
4199 | * called from enqueue/dequeue and updates the hrtick when the | |
4200 | * current task is from our class and nr_running is low enough | |
4201 | * to matter. | |
4202 | */ | |
4203 | static void hrtick_update(struct rq *rq) | |
4204 | { | |
4205 | struct task_struct *curr = rq->curr; | |
4206 | ||
4207 | if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) | |
4208 | return; | |
4209 | ||
4210 | if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) | |
4211 | hrtick_start_fair(rq, curr); | |
4212 | } | |
4213 | #else /* !CONFIG_SCHED_HRTICK */ | |
4214 | static inline void | |
4215 | hrtick_start_fair(struct rq *rq, struct task_struct *p) | |
4216 | { | |
4217 | } | |
4218 | ||
4219 | static inline void hrtick_update(struct rq *rq) | |
4220 | { | |
4221 | } | |
4222 | #endif | |
4223 | ||
4224 | /* | |
4225 | * The enqueue_task method is called before nr_running is | |
4226 | * increased. Here we update the fair scheduling stats and | |
4227 | * then put the task into the rbtree: | |
4228 | */ | |
4229 | static void | |
4230 | enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) | |
4231 | { | |
4232 | struct cfs_rq *cfs_rq; | |
4233 | struct sched_entity *se = &p->se; | |
4234 | ||
4235 | for_each_sched_entity(se) { | |
4236 | if (se->on_rq) | |
4237 | break; | |
4238 | cfs_rq = cfs_rq_of(se); | |
4239 | enqueue_entity(cfs_rq, se, flags); | |
4240 | ||
4241 | /* | |
4242 | * end evaluation on encountering a throttled cfs_rq | |
4243 | * | |
4244 | * note: in the case of encountering a throttled cfs_rq we will | |
4245 | * post the final h_nr_running increment below. | |
4246 | */ | |
4247 | if (cfs_rq_throttled(cfs_rq)) | |
4248 | break; | |
4249 | cfs_rq->h_nr_running++; | |
4250 | ||
4251 | flags = ENQUEUE_WAKEUP; | |
4252 | } | |
4253 | ||
4254 | for_each_sched_entity(se) { | |
4255 | cfs_rq = cfs_rq_of(se); | |
4256 | cfs_rq->h_nr_running++; | |
4257 | ||
4258 | if (cfs_rq_throttled(cfs_rq)) | |
4259 | break; | |
4260 | ||
4261 | update_cfs_shares(cfs_rq); | |
4262 | update_entity_load_avg(se, 1); | |
4263 | } | |
4264 | ||
4265 | if (!se) { | |
4266 | update_rq_runnable_avg(rq, rq->nr_running); | |
4267 | add_nr_running(rq, 1); | |
4268 | } | |
4269 | hrtick_update(rq); | |
4270 | } | |
4271 | ||
4272 | static void set_next_buddy(struct sched_entity *se); | |
4273 | ||
4274 | /* | |
4275 | * The dequeue_task method is called before nr_running is | |
4276 | * decreased. We remove the task from the rbtree and | |
4277 | * update the fair scheduling stats: | |
4278 | */ | |
4279 | static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) | |
4280 | { | |
4281 | struct cfs_rq *cfs_rq; | |
4282 | struct sched_entity *se = &p->se; | |
4283 | int task_sleep = flags & DEQUEUE_SLEEP; | |
4284 | ||
4285 | for_each_sched_entity(se) { | |
4286 | cfs_rq = cfs_rq_of(se); | |
4287 | dequeue_entity(cfs_rq, se, flags); | |
4288 | ||
4289 | /* | |
4290 | * end evaluation on encountering a throttled cfs_rq | |
4291 | * | |
4292 | * note: in the case of encountering a throttled cfs_rq we will | |
4293 | * post the final h_nr_running decrement below. | |
4294 | */ | |
4295 | if (cfs_rq_throttled(cfs_rq)) | |
4296 | break; | |
4297 | cfs_rq->h_nr_running--; | |
4298 | ||
4299 | /* Don't dequeue parent if it has other entities besides us */ | |
4300 | if (cfs_rq->load.weight) { | |
4301 | /* | |
4302 | * Bias pick_next to pick a task from this cfs_rq, as | |
4303 | * p is sleeping when it is within its sched_slice. | |
4304 | */ | |
4305 | if (task_sleep && parent_entity(se)) | |
4306 | set_next_buddy(parent_entity(se)); | |
4307 | ||
4308 | /* avoid re-evaluating load for this entity */ | |
4309 | se = parent_entity(se); | |
4310 | break; | |
4311 | } | |
4312 | flags |= DEQUEUE_SLEEP; | |
4313 | } | |
4314 | ||
4315 | for_each_sched_entity(se) { | |
4316 | cfs_rq = cfs_rq_of(se); | |
4317 | cfs_rq->h_nr_running--; | |
4318 | ||
4319 | if (cfs_rq_throttled(cfs_rq)) | |
4320 | break; | |
4321 | ||
4322 | update_cfs_shares(cfs_rq); | |
4323 | update_entity_load_avg(se, 1); | |
4324 | } | |
4325 | ||
4326 | if (!se) { | |
4327 | sub_nr_running(rq, 1); | |
4328 | update_rq_runnable_avg(rq, 1); | |
4329 | } | |
4330 | hrtick_update(rq); | |
4331 | } | |
4332 | ||
4333 | #ifdef CONFIG_SMP | |
4334 | ||
4335 | /* | |
4336 | * per rq 'load' arrray crap; XXX kill this. | |
4337 | */ | |
4338 | ||
4339 | /* | |
4340 | * The exact cpuload at various idx values, calculated at every tick would be | |
4341 | * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load | |
4342 | * | |
4343 | * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called | |
4344 | * on nth tick when cpu may be busy, then we have: | |
4345 | * load = ((2^idx - 1) / 2^idx)^(n-1) * load | |
4346 | * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load | |
4347 | * | |
4348 | * decay_load_missed() below does efficient calculation of | |
4349 | * load = ((2^idx - 1) / 2^idx)^(n-1) * load | |
4350 | * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load | |
4351 | * | |
4352 | * The calculation is approximated on a 128 point scale. | |
4353 | * degrade_zero_ticks is the number of ticks after which load at any | |
4354 | * particular idx is approximated to be zero. | |
4355 | * degrade_factor is a precomputed table, a row for each load idx. | |
4356 | * Each column corresponds to degradation factor for a power of two ticks, | |
4357 | * based on 128 point scale. | |
4358 | * Example: | |
4359 | * row 2, col 3 (=12) says that the degradation at load idx 2 after | |
4360 | * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8). | |
4361 | * | |
4362 | * With this power of 2 load factors, we can degrade the load n times | |
4363 | * by looking at 1 bits in n and doing as many mult/shift instead of | |
4364 | * n mult/shifts needed by the exact degradation. | |
4365 | */ | |
4366 | #define DEGRADE_SHIFT 7 | |
4367 | static const unsigned char | |
4368 | degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128}; | |
4369 | static const unsigned char | |
4370 | degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = { | |
4371 | {0, 0, 0, 0, 0, 0, 0, 0}, | |
4372 | {64, 32, 8, 0, 0, 0, 0, 0}, | |
4373 | {96, 72, 40, 12, 1, 0, 0}, | |
4374 | {112, 98, 75, 43, 15, 1, 0}, | |
4375 | {120, 112, 98, 76, 45, 16, 2} }; | |
4376 | ||
4377 | /* | |
4378 | * Update cpu_load for any missed ticks, due to tickless idle. The backlog | |
4379 | * would be when CPU is idle and so we just decay the old load without | |
4380 | * adding any new load. | |
4381 | */ | |
4382 | static unsigned long | |
4383 | decay_load_missed(unsigned long load, unsigned long missed_updates, int idx) | |
4384 | { | |
4385 | int j = 0; | |
4386 | ||
4387 | if (!missed_updates) | |
4388 | return load; | |
4389 | ||
4390 | if (missed_updates >= degrade_zero_ticks[idx]) | |
4391 | return 0; | |
4392 | ||
4393 | if (idx == 1) | |
4394 | return load >> missed_updates; | |
4395 | ||
4396 | while (missed_updates) { | |
4397 | if (missed_updates % 2) | |
4398 | load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT; | |
4399 | ||
4400 | missed_updates >>= 1; | |
4401 | j++; | |
4402 | } | |
4403 | return load; | |
4404 | } | |
4405 | ||
4406 | /* | |
4407 | * Update rq->cpu_load[] statistics. This function is usually called every | |
4408 | * scheduler tick (TICK_NSEC). With tickless idle this will not be called | |
4409 | * every tick. We fix it up based on jiffies. | |
4410 | */ | |
4411 | static void __update_cpu_load(struct rq *this_rq, unsigned long this_load, | |
4412 | unsigned long pending_updates) | |
4413 | { | |
4414 | int i, scale; | |
4415 | ||
4416 | this_rq->nr_load_updates++; | |
4417 | ||
4418 | /* Update our load: */ | |
4419 | this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */ | |
4420 | for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) { | |
4421 | unsigned long old_load, new_load; | |
4422 | ||
4423 | /* scale is effectively 1 << i now, and >> i divides by scale */ | |
4424 | ||
4425 | old_load = this_rq->cpu_load[i]; | |
4426 | old_load = decay_load_missed(old_load, pending_updates - 1, i); | |
4427 | new_load = this_load; | |
4428 | /* | |
4429 | * Round up the averaging division if load is increasing. This | |
4430 | * prevents us from getting stuck on 9 if the load is 10, for | |
4431 | * example. | |
4432 | */ | |
4433 | if (new_load > old_load) | |
4434 | new_load += scale - 1; | |
4435 | ||
4436 | this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i; | |
4437 | } | |
4438 | ||
4439 | sched_avg_update(this_rq); | |
4440 | } | |
4441 | ||
4442 | #ifdef CONFIG_NO_HZ_COMMON | |
4443 | /* | |
4444 | * There is no sane way to deal with nohz on smp when using jiffies because the | |
4445 | * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading | |
4446 | * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}. | |
4447 | * | |
4448 | * Therefore we cannot use the delta approach from the regular tick since that | |
4449 | * would seriously skew the load calculation. However we'll make do for those | |
4450 | * updates happening while idle (nohz_idle_balance) or coming out of idle | |
4451 | * (tick_nohz_idle_exit). | |
4452 | * | |
4453 | * This means we might still be one tick off for nohz periods. | |
4454 | */ | |
4455 | ||
4456 | /* | |
4457 | * Called from nohz_idle_balance() to update the load ratings before doing the | |
4458 | * idle balance. | |
4459 | */ | |
4460 | static void update_idle_cpu_load(struct rq *this_rq) | |
4461 | { | |
4462 | unsigned long curr_jiffies = READ_ONCE(jiffies); | |
4463 | unsigned long load = this_rq->cfs.runnable_load_avg; | |
4464 | unsigned long pending_updates; | |
4465 | ||
4466 | /* | |
4467 | * bail if there's load or we're actually up-to-date. | |
4468 | */ | |
4469 | if (load || curr_jiffies == this_rq->last_load_update_tick) | |
4470 | return; | |
4471 | ||
4472 | pending_updates = curr_jiffies - this_rq->last_load_update_tick; | |
4473 | this_rq->last_load_update_tick = curr_jiffies; | |
4474 | ||
4475 | __update_cpu_load(this_rq, load, pending_updates); | |
4476 | } | |
4477 | ||
4478 | /* | |
4479 | * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed. | |
4480 | */ | |
4481 | void update_cpu_load_nohz(void) | |
4482 | { | |
4483 | struct rq *this_rq = this_rq(); | |
4484 | unsigned long curr_jiffies = READ_ONCE(jiffies); | |
4485 | unsigned long pending_updates; | |
4486 | ||
4487 | if (curr_jiffies == this_rq->last_load_update_tick) | |
4488 | return; | |
4489 | ||
4490 | raw_spin_lock(&this_rq->lock); | |
4491 | pending_updates = curr_jiffies - this_rq->last_load_update_tick; | |
4492 | if (pending_updates) { | |
4493 | this_rq->last_load_update_tick = curr_jiffies; | |
4494 | /* | |
4495 | * We were idle, this means load 0, the current load might be | |
4496 | * !0 due to remote wakeups and the sort. | |
4497 | */ | |
4498 | __update_cpu_load(this_rq, 0, pending_updates); | |
4499 | } | |
4500 | raw_spin_unlock(&this_rq->lock); | |
4501 | } | |
4502 | #endif /* CONFIG_NO_HZ */ | |
4503 | ||
4504 | /* | |
4505 | * Called from scheduler_tick() | |
4506 | */ | |
4507 | void update_cpu_load_active(struct rq *this_rq) | |
4508 | { | |
4509 | unsigned long load = this_rq->cfs.runnable_load_avg; | |
4510 | /* | |
4511 | * See the mess around update_idle_cpu_load() / update_cpu_load_nohz(). | |
4512 | */ | |
4513 | this_rq->last_load_update_tick = jiffies; | |
4514 | __update_cpu_load(this_rq, load, 1); | |
4515 | } | |
4516 | ||
4517 | /* Used instead of source_load when we know the type == 0 */ | |
4518 | static unsigned long weighted_cpuload(const int cpu) | |
4519 | { | |
4520 | return cpu_rq(cpu)->cfs.runnable_load_avg; | |
4521 | } | |
4522 | ||
4523 | /* | |
4524 | * Return a low guess at the load of a migration-source cpu weighted | |
4525 | * according to the scheduling class and "nice" value. | |
4526 | * | |
4527 | * We want to under-estimate the load of migration sources, to | |
4528 | * balance conservatively. | |
4529 | */ | |
4530 | static unsigned long source_load(int cpu, int type) | |
4531 | { | |
4532 | struct rq *rq = cpu_rq(cpu); | |
4533 | unsigned long total = weighted_cpuload(cpu); | |
4534 | ||
4535 | if (type == 0 || !sched_feat(LB_BIAS)) | |
4536 | return total; | |
4537 | ||
4538 | return min(rq->cpu_load[type-1], total); | |
4539 | } | |
4540 | ||
4541 | /* | |
4542 | * Return a high guess at the load of a migration-target cpu weighted | |
4543 | * according to the scheduling class and "nice" value. | |
4544 | */ | |
4545 | static unsigned long target_load(int cpu, int type) | |
4546 | { | |
4547 | struct rq *rq = cpu_rq(cpu); | |
4548 | unsigned long total = weighted_cpuload(cpu); | |
4549 | ||
4550 | if (type == 0 || !sched_feat(LB_BIAS)) | |
4551 | return total; | |
4552 | ||
4553 | return max(rq->cpu_load[type-1], total); | |
4554 | } | |
4555 | ||
4556 | static unsigned long capacity_of(int cpu) | |
4557 | { | |
4558 | return cpu_rq(cpu)->cpu_capacity; | |
4559 | } | |
4560 | ||
4561 | static unsigned long capacity_orig_of(int cpu) | |
4562 | { | |
4563 | return cpu_rq(cpu)->cpu_capacity_orig; | |
4564 | } | |
4565 | ||
4566 | static unsigned long cpu_avg_load_per_task(int cpu) | |
4567 | { | |
4568 | struct rq *rq = cpu_rq(cpu); | |
4569 | unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running); | |
4570 | unsigned long load_avg = rq->cfs.runnable_load_avg; | |
4571 | ||
4572 | if (nr_running) | |
4573 | return load_avg / nr_running; | |
4574 | ||
4575 | return 0; | |
4576 | } | |
4577 | ||
4578 | static void record_wakee(struct task_struct *p) | |
4579 | { | |
4580 | /* | |
4581 | * Rough decay (wiping) for cost saving, don't worry | |
4582 | * about the boundary, really active task won't care | |
4583 | * about the loss. | |
4584 | */ | |
4585 | if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) { | |
4586 | current->wakee_flips >>= 1; | |
4587 | current->wakee_flip_decay_ts = jiffies; | |
4588 | } | |
4589 | ||
4590 | if (current->last_wakee != p) { | |
4591 | current->last_wakee = p; | |
4592 | current->wakee_flips++; | |
4593 | } | |
4594 | } | |
4595 | ||
4596 | static void task_waking_fair(struct task_struct *p) | |
4597 | { | |
4598 | struct sched_entity *se = &p->se; | |
4599 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
4600 | u64 min_vruntime; | |
4601 | ||
4602 | #ifndef CONFIG_64BIT | |
4603 | u64 min_vruntime_copy; | |
4604 | ||
4605 | do { | |
4606 | min_vruntime_copy = cfs_rq->min_vruntime_copy; | |
4607 | smp_rmb(); | |
4608 | min_vruntime = cfs_rq->min_vruntime; | |
4609 | } while (min_vruntime != min_vruntime_copy); | |
4610 | #else | |
4611 | min_vruntime = cfs_rq->min_vruntime; | |
4612 | #endif | |
4613 | ||
4614 | se->vruntime -= min_vruntime; | |
4615 | record_wakee(p); | |
4616 | } | |
4617 | ||
4618 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
4619 | /* | |
4620 | * effective_load() calculates the load change as seen from the root_task_group | |
4621 | * | |
4622 | * Adding load to a group doesn't make a group heavier, but can cause movement | |
4623 | * of group shares between cpus. Assuming the shares were perfectly aligned one | |
4624 | * can calculate the shift in shares. | |
4625 | * | |
4626 | * Calculate the effective load difference if @wl is added (subtracted) to @tg | |
4627 | * on this @cpu and results in a total addition (subtraction) of @wg to the | |
4628 | * total group weight. | |
4629 | * | |
4630 | * Given a runqueue weight distribution (rw_i) we can compute a shares | |
4631 | * distribution (s_i) using: | |
4632 | * | |
4633 | * s_i = rw_i / \Sum rw_j (1) | |
4634 | * | |
4635 | * Suppose we have 4 CPUs and our @tg is a direct child of the root group and | |
4636 | * has 7 equal weight tasks, distributed as below (rw_i), with the resulting | |
4637 | * shares distribution (s_i): | |
4638 | * | |
4639 | * rw_i = { 2, 4, 1, 0 } | |
4640 | * s_i = { 2/7, 4/7, 1/7, 0 } | |
4641 | * | |
4642 | * As per wake_affine() we're interested in the load of two CPUs (the CPU the | |
4643 | * task used to run on and the CPU the waker is running on), we need to | |
4644 | * compute the effect of waking a task on either CPU and, in case of a sync | |
4645 | * wakeup, compute the effect of the current task going to sleep. | |
4646 | * | |
4647 | * So for a change of @wl to the local @cpu with an overall group weight change | |
4648 | * of @wl we can compute the new shares distribution (s'_i) using: | |
4649 | * | |
4650 | * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2) | |
4651 | * | |
4652 | * Suppose we're interested in CPUs 0 and 1, and want to compute the load | |
4653 | * differences in waking a task to CPU 0. The additional task changes the | |
4654 | * weight and shares distributions like: | |
4655 | * | |
4656 | * rw'_i = { 3, 4, 1, 0 } | |
4657 | * s'_i = { 3/8, 4/8, 1/8, 0 } | |
4658 | * | |
4659 | * We can then compute the difference in effective weight by using: | |
4660 | * | |
4661 | * dw_i = S * (s'_i - s_i) (3) | |
4662 | * | |
4663 | * Where 'S' is the group weight as seen by its parent. | |
4664 | * | |
4665 | * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7) | |
4666 | * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 - | |
4667 | * 4/7) times the weight of the group. | |
4668 | */ | |
4669 | static long effective_load(struct task_group *tg, int cpu, long wl, long wg) | |
4670 | { | |
4671 | struct sched_entity *se = tg->se[cpu]; | |
4672 | ||
4673 | if (!tg->parent) /* the trivial, non-cgroup case */ | |
4674 | return wl; | |
4675 | ||
4676 | for_each_sched_entity(se) { | |
4677 | long w, W; | |
4678 | ||
4679 | tg = se->my_q->tg; | |
4680 | ||
4681 | /* | |
4682 | * W = @wg + \Sum rw_j | |
4683 | */ | |
4684 | W = wg + calc_tg_weight(tg, se->my_q); | |
4685 | ||
4686 | /* | |
4687 | * w = rw_i + @wl | |
4688 | */ | |
4689 | w = se->my_q->load.weight + wl; | |
4690 | ||
4691 | /* | |
4692 | * wl = S * s'_i; see (2) | |
4693 | */ | |
4694 | if (W > 0 && w < W) | |
4695 | wl = (w * (long)tg->shares) / W; | |
4696 | else | |
4697 | wl = tg->shares; | |
4698 | ||
4699 | /* | |
4700 | * Per the above, wl is the new se->load.weight value; since | |
4701 | * those are clipped to [MIN_SHARES, ...) do so now. See | |
4702 | * calc_cfs_shares(). | |
4703 | */ | |
4704 | if (wl < MIN_SHARES) | |
4705 | wl = MIN_SHARES; | |
4706 | ||
4707 | /* | |
4708 | * wl = dw_i = S * (s'_i - s_i); see (3) | |
4709 | */ | |
4710 | wl -= se->load.weight; | |
4711 | ||
4712 | /* | |
4713 | * Recursively apply this logic to all parent groups to compute | |
4714 | * the final effective load change on the root group. Since | |
4715 | * only the @tg group gets extra weight, all parent groups can | |
4716 | * only redistribute existing shares. @wl is the shift in shares | |
4717 | * resulting from this level per the above. | |
4718 | */ | |
4719 | wg = 0; | |
4720 | } | |
4721 | ||
4722 | return wl; | |
4723 | } | |
4724 | #else | |
4725 | ||
4726 | static long effective_load(struct task_group *tg, int cpu, long wl, long wg) | |
4727 | { | |
4728 | return wl; | |
4729 | } | |
4730 | ||
4731 | #endif | |
4732 | ||
4733 | static int wake_wide(struct task_struct *p) | |
4734 | { | |
4735 | int factor = this_cpu_read(sd_llc_size); | |
4736 | ||
4737 | /* | |
4738 | * Yeah, it's the switching-frequency, could means many wakee or | |
4739 | * rapidly switch, use factor here will just help to automatically | |
4740 | * adjust the loose-degree, so bigger node will lead to more pull. | |
4741 | */ | |
4742 | if (p->wakee_flips > factor) { | |
4743 | /* | |
4744 | * wakee is somewhat hot, it needs certain amount of cpu | |
4745 | * resource, so if waker is far more hot, prefer to leave | |
4746 | * it alone. | |
4747 | */ | |
4748 | if (current->wakee_flips > (factor * p->wakee_flips)) | |
4749 | return 1; | |
4750 | } | |
4751 | ||
4752 | return 0; | |
4753 | } | |
4754 | ||
4755 | static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) | |
4756 | { | |
4757 | s64 this_load, load; | |
4758 | s64 this_eff_load, prev_eff_load; | |
4759 | int idx, this_cpu, prev_cpu; | |
4760 | struct task_group *tg; | |
4761 | unsigned long weight; | |
4762 | int balanced; | |
4763 | ||
4764 | /* | |
4765 | * If we wake multiple tasks be careful to not bounce | |
4766 | * ourselves around too much. | |
4767 | */ | |
4768 | if (wake_wide(p)) | |
4769 | return 0; | |
4770 | ||
4771 | idx = sd->wake_idx; | |
4772 | this_cpu = smp_processor_id(); | |
4773 | prev_cpu = task_cpu(p); | |
4774 | load = source_load(prev_cpu, idx); | |
4775 | this_load = target_load(this_cpu, idx); | |
4776 | ||
4777 | /* | |
4778 | * If sync wakeup then subtract the (maximum possible) | |
4779 | * effect of the currently running task from the load | |
4780 | * of the current CPU: | |
4781 | */ | |
4782 | if (sync) { | |
4783 | tg = task_group(current); | |
4784 | weight = current->se.load.weight; | |
4785 | ||
4786 | this_load += effective_load(tg, this_cpu, -weight, -weight); | |
4787 | load += effective_load(tg, prev_cpu, 0, -weight); | |
4788 | } | |
4789 | ||
4790 | tg = task_group(p); | |
4791 | weight = p->se.load.weight; | |
4792 | ||
4793 | /* | |
4794 | * In low-load situations, where prev_cpu is idle and this_cpu is idle | |
4795 | * due to the sync cause above having dropped this_load to 0, we'll | |
4796 | * always have an imbalance, but there's really nothing you can do | |
4797 | * about that, so that's good too. | |
4798 | * | |
4799 | * Otherwise check if either cpus are near enough in load to allow this | |
4800 | * task to be woken on this_cpu. | |
4801 | */ | |
4802 | this_eff_load = 100; | |
4803 | this_eff_load *= capacity_of(prev_cpu); | |
4804 | ||
4805 | prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2; | |
4806 | prev_eff_load *= capacity_of(this_cpu); | |
4807 | ||
4808 | if (this_load > 0) { | |
4809 | this_eff_load *= this_load + | |
4810 | effective_load(tg, this_cpu, weight, weight); | |
4811 | ||
4812 | prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight); | |
4813 | } | |
4814 | ||
4815 | balanced = this_eff_load <= prev_eff_load; | |
4816 | ||
4817 | schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts); | |
4818 | ||
4819 | if (!balanced) | |
4820 | return 0; | |
4821 | ||
4822 | schedstat_inc(sd, ttwu_move_affine); | |
4823 | schedstat_inc(p, se.statistics.nr_wakeups_affine); | |
4824 | ||
4825 | return 1; | |
4826 | } | |
4827 | ||
4828 | /* | |
4829 | * find_idlest_group finds and returns the least busy CPU group within the | |
4830 | * domain. | |
4831 | */ | |
4832 | static struct sched_group * | |
4833 | find_idlest_group(struct sched_domain *sd, struct task_struct *p, | |
4834 | int this_cpu, int sd_flag) | |
4835 | { | |
4836 | struct sched_group *idlest = NULL, *group = sd->groups; | |
4837 | unsigned long min_load = ULONG_MAX, this_load = 0; | |
4838 | int load_idx = sd->forkexec_idx; | |
4839 | int imbalance = 100 + (sd->imbalance_pct-100)/2; | |
4840 | ||
4841 | if (sd_flag & SD_BALANCE_WAKE) | |
4842 | load_idx = sd->wake_idx; | |
4843 | ||
4844 | do { | |
4845 | unsigned long load, avg_load; | |
4846 | int local_group; | |
4847 | int i; | |
4848 | ||
4849 | /* Skip over this group if it has no CPUs allowed */ | |
4850 | if (!cpumask_intersects(sched_group_cpus(group), | |
4851 | tsk_cpus_allowed(p))) | |
4852 | continue; | |
4853 | ||
4854 | local_group = cpumask_test_cpu(this_cpu, | |
4855 | sched_group_cpus(group)); | |
4856 | ||
4857 | /* Tally up the load of all CPUs in the group */ | |
4858 | avg_load = 0; | |
4859 | ||
4860 | for_each_cpu(i, sched_group_cpus(group)) { | |
4861 | /* Bias balancing toward cpus of our domain */ | |
4862 | if (local_group) | |
4863 | load = source_load(i, load_idx); | |
4864 | else | |
4865 | load = target_load(i, load_idx); | |
4866 | ||
4867 | avg_load += load; | |
4868 | } | |
4869 | ||
4870 | /* Adjust by relative CPU capacity of the group */ | |
4871 | avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity; | |
4872 | ||
4873 | if (local_group) { | |
4874 | this_load = avg_load; | |
4875 | } else if (avg_load < min_load) { | |
4876 | min_load = avg_load; | |
4877 | idlest = group; | |
4878 | } | |
4879 | } while (group = group->next, group != sd->groups); | |
4880 | ||
4881 | if (!idlest || 100*this_load < imbalance*min_load) | |
4882 | return NULL; | |
4883 | return idlest; | |
4884 | } | |
4885 | ||
4886 | /* | |
4887 | * find_idlest_cpu - find the idlest cpu among the cpus in group. | |
4888 | */ | |
4889 | static int | |
4890 | find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) | |
4891 | { | |
4892 | unsigned long load, min_load = ULONG_MAX; | |
4893 | unsigned int min_exit_latency = UINT_MAX; | |
4894 | u64 latest_idle_timestamp = 0; | |
4895 | int least_loaded_cpu = this_cpu; | |
4896 | int shallowest_idle_cpu = -1; | |
4897 | int i; | |
4898 | ||
4899 | /* Traverse only the allowed CPUs */ | |
4900 | for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { | |
4901 | if (idle_cpu(i)) { | |
4902 | struct rq *rq = cpu_rq(i); | |
4903 | struct cpuidle_state *idle = idle_get_state(rq); | |
4904 | if (idle && idle->exit_latency < min_exit_latency) { | |
4905 | /* | |
4906 | * We give priority to a CPU whose idle state | |
4907 | * has the smallest exit latency irrespective | |
4908 | * of any idle timestamp. | |
4909 | */ | |
4910 | min_exit_latency = idle->exit_latency; | |
4911 | latest_idle_timestamp = rq->idle_stamp; | |
4912 | shallowest_idle_cpu = i; | |
4913 | } else if ((!idle || idle->exit_latency == min_exit_latency) && | |
4914 | rq->idle_stamp > latest_idle_timestamp) { | |
4915 | /* | |
4916 | * If equal or no active idle state, then | |
4917 | * the most recently idled CPU might have | |
4918 | * a warmer cache. | |
4919 | */ | |
4920 | latest_idle_timestamp = rq->idle_stamp; | |
4921 | shallowest_idle_cpu = i; | |
4922 | } | |
4923 | } else if (shallowest_idle_cpu == -1) { | |
4924 | load = weighted_cpuload(i); | |
4925 | if (load < min_load || (load == min_load && i == this_cpu)) { | |
4926 | min_load = load; | |
4927 | least_loaded_cpu = i; | |
4928 | } | |
4929 | } | |
4930 | } | |
4931 | ||
4932 | return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; | |
4933 | } | |
4934 | ||
4935 | /* | |
4936 | * Try and locate an idle CPU in the sched_domain. | |
4937 | */ | |
4938 | static int select_idle_sibling(struct task_struct *p, int target) | |
4939 | { | |
4940 | struct sched_domain *sd; | |
4941 | struct sched_group *sg; | |
4942 | int i = task_cpu(p); | |
4943 | ||
4944 | if (idle_cpu(target)) | |
4945 | return target; | |
4946 | ||
4947 | /* | |
4948 | * If the prevous cpu is cache affine and idle, don't be stupid. | |
4949 | */ | |
4950 | if (i != target && cpus_share_cache(i, target) && idle_cpu(i)) | |
4951 | return i; | |
4952 | ||
4953 | /* | |
4954 | * Otherwise, iterate the domains and find an elegible idle cpu. | |
4955 | */ | |
4956 | sd = rcu_dereference(per_cpu(sd_llc, target)); | |
4957 | for_each_lower_domain(sd) { | |
4958 | sg = sd->groups; | |
4959 | do { | |
4960 | if (!cpumask_intersects(sched_group_cpus(sg), | |
4961 | tsk_cpus_allowed(p))) | |
4962 | goto next; | |
4963 | ||
4964 | for_each_cpu(i, sched_group_cpus(sg)) { | |
4965 | if (i == target || !idle_cpu(i)) | |
4966 | goto next; | |
4967 | } | |
4968 | ||
4969 | target = cpumask_first_and(sched_group_cpus(sg), | |
4970 | tsk_cpus_allowed(p)); | |
4971 | goto done; | |
4972 | next: | |
4973 | sg = sg->next; | |
4974 | } while (sg != sd->groups); | |
4975 | } | |
4976 | done: | |
4977 | return target; | |
4978 | } | |
4979 | /* | |
4980 | * get_cpu_usage returns the amount of capacity of a CPU that is used by CFS | |
4981 | * tasks. The unit of the return value must be the one of capacity so we can | |
4982 | * compare the usage with the capacity of the CPU that is available for CFS | |
4983 | * task (ie cpu_capacity). | |
4984 | * cfs.utilization_load_avg is the sum of running time of runnable tasks on a | |
4985 | * CPU. It represents the amount of utilization of a CPU in the range | |
4986 | * [0..SCHED_LOAD_SCALE]. The usage of a CPU can't be higher than the full | |
4987 | * capacity of the CPU because it's about the running time on this CPU. | |
4988 | * Nevertheless, cfs.utilization_load_avg can be higher than SCHED_LOAD_SCALE | |
4989 | * because of unfortunate rounding in avg_period and running_load_avg or just | |
4990 | * after migrating tasks until the average stabilizes with the new running | |
4991 | * time. So we need to check that the usage stays into the range | |
4992 | * [0..cpu_capacity_orig] and cap if necessary. | |
4993 | * Without capping the usage, a group could be seen as overloaded (CPU0 usage | |
4994 | * at 121% + CPU1 usage at 80%) whereas CPU1 has 20% of available capacity | |
4995 | */ | |
4996 | static int get_cpu_usage(int cpu) | |
4997 | { | |
4998 | unsigned long usage = cpu_rq(cpu)->cfs.utilization_load_avg; | |
4999 | unsigned long capacity = capacity_orig_of(cpu); | |
5000 | ||
5001 | if (usage >= SCHED_LOAD_SCALE) | |
5002 | return capacity; | |
5003 | ||
5004 | return (usage * capacity) >> SCHED_LOAD_SHIFT; | |
5005 | } | |
5006 | ||
5007 | /* | |
5008 | * select_task_rq_fair: Select target runqueue for the waking task in domains | |
5009 | * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE, | |
5010 | * SD_BALANCE_FORK, or SD_BALANCE_EXEC. | |
5011 | * | |
5012 | * Balances load by selecting the idlest cpu in the idlest group, or under | |
5013 | * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set. | |
5014 | * | |
5015 | * Returns the target cpu number. | |
5016 | * | |
5017 | * preempt must be disabled. | |
5018 | */ | |
5019 | static int | |
5020 | select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags) | |
5021 | { | |
5022 | struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL; | |
5023 | int cpu = smp_processor_id(); | |
5024 | int new_cpu = cpu; | |
5025 | int want_affine = 0; | |
5026 | int sync = wake_flags & WF_SYNC; | |
5027 | ||
5028 | if (sd_flag & SD_BALANCE_WAKE) | |
5029 | want_affine = cpumask_test_cpu(cpu, tsk_cpus_allowed(p)); | |
5030 | ||
5031 | rcu_read_lock(); | |
5032 | for_each_domain(cpu, tmp) { | |
5033 | if (!(tmp->flags & SD_LOAD_BALANCE)) | |
5034 | continue; | |
5035 | ||
5036 | /* | |
5037 | * If both cpu and prev_cpu are part of this domain, | |
5038 | * cpu is a valid SD_WAKE_AFFINE target. | |
5039 | */ | |
5040 | if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && | |
5041 | cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { | |
5042 | affine_sd = tmp; | |
5043 | break; | |
5044 | } | |
5045 | ||
5046 | if (tmp->flags & sd_flag) | |
5047 | sd = tmp; | |
5048 | } | |
5049 | ||
5050 | if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync)) | |
5051 | prev_cpu = cpu; | |
5052 | ||
5053 | if (sd_flag & SD_BALANCE_WAKE) { | |
5054 | new_cpu = select_idle_sibling(p, prev_cpu); | |
5055 | goto unlock; | |
5056 | } | |
5057 | ||
5058 | while (sd) { | |
5059 | struct sched_group *group; | |
5060 | int weight; | |
5061 | ||
5062 | if (!(sd->flags & sd_flag)) { | |
5063 | sd = sd->child; | |
5064 | continue; | |
5065 | } | |
5066 | ||
5067 | group = find_idlest_group(sd, p, cpu, sd_flag); | |
5068 | if (!group) { | |
5069 | sd = sd->child; | |
5070 | continue; | |
5071 | } | |
5072 | ||
5073 | new_cpu = find_idlest_cpu(group, p, cpu); | |
5074 | if (new_cpu == -1 || new_cpu == cpu) { | |
5075 | /* Now try balancing at a lower domain level of cpu */ | |
5076 | sd = sd->child; | |
5077 | continue; | |
5078 | } | |
5079 | ||
5080 | /* Now try balancing at a lower domain level of new_cpu */ | |
5081 | cpu = new_cpu; | |
5082 | weight = sd->span_weight; | |
5083 | sd = NULL; | |
5084 | for_each_domain(cpu, tmp) { | |
5085 | if (weight <= tmp->span_weight) | |
5086 | break; | |
5087 | if (tmp->flags & sd_flag) | |
5088 | sd = tmp; | |
5089 | } | |
5090 | /* while loop will break here if sd == NULL */ | |
5091 | } | |
5092 | unlock: | |
5093 | rcu_read_unlock(); | |
5094 | ||
5095 | return new_cpu; | |
5096 | } | |
5097 | ||
5098 | /* | |
5099 | * Called immediately before a task is migrated to a new cpu; task_cpu(p) and | |
5100 | * cfs_rq_of(p) references at time of call are still valid and identify the | |
5101 | * previous cpu. However, the caller only guarantees p->pi_lock is held; no | |
5102 | * other assumptions, including the state of rq->lock, should be made. | |
5103 | */ | |
5104 | static void | |
5105 | migrate_task_rq_fair(struct task_struct *p, int next_cpu) | |
5106 | { | |
5107 | struct sched_entity *se = &p->se; | |
5108 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
5109 | ||
5110 | /* | |
5111 | * Load tracking: accumulate removed load so that it can be processed | |
5112 | * when we next update owning cfs_rq under rq->lock. Tasks contribute | |
5113 | * to blocked load iff they have a positive decay-count. It can never | |
5114 | * be negative here since on-rq tasks have decay-count == 0. | |
5115 | */ | |
5116 | if (se->avg.decay_count) { | |
5117 | se->avg.decay_count = -__synchronize_entity_decay(se); | |
5118 | atomic_long_add(se->avg.load_avg_contrib, | |
5119 | &cfs_rq->removed_load); | |
5120 | } | |
5121 | ||
5122 | /* We have migrated, no longer consider this task hot */ | |
5123 | se->exec_start = 0; | |
5124 | } | |
5125 | #endif /* CONFIG_SMP */ | |
5126 | ||
5127 | static unsigned long | |
5128 | wakeup_gran(struct sched_entity *curr, struct sched_entity *se) | |
5129 | { | |
5130 | unsigned long gran = sysctl_sched_wakeup_granularity; | |
5131 | ||
5132 | /* | |
5133 | * Since its curr running now, convert the gran from real-time | |
5134 | * to virtual-time in his units. | |
5135 | * | |
5136 | * By using 'se' instead of 'curr' we penalize light tasks, so | |
5137 | * they get preempted easier. That is, if 'se' < 'curr' then | |
5138 | * the resulting gran will be larger, therefore penalizing the | |
5139 | * lighter, if otoh 'se' > 'curr' then the resulting gran will | |
5140 | * be smaller, again penalizing the lighter task. | |
5141 | * | |
5142 | * This is especially important for buddies when the leftmost | |
5143 | * task is higher priority than the buddy. | |
5144 | */ | |
5145 | return calc_delta_fair(gran, se); | |
5146 | } | |
5147 | ||
5148 | /* | |
5149 | * Should 'se' preempt 'curr'. | |
5150 | * | |
5151 | * |s1 | |
5152 | * |s2 | |
5153 | * |s3 | |
5154 | * g | |
5155 | * |<--->|c | |
5156 | * | |
5157 | * w(c, s1) = -1 | |
5158 | * w(c, s2) = 0 | |
5159 | * w(c, s3) = 1 | |
5160 | * | |
5161 | */ | |
5162 | static int | |
5163 | wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) | |
5164 | { | |
5165 | s64 gran, vdiff = curr->vruntime - se->vruntime; | |
5166 | ||
5167 | if (vdiff <= 0) | |
5168 | return -1; | |
5169 | ||
5170 | gran = wakeup_gran(curr, se); | |
5171 | if (vdiff > gran) | |
5172 | return 1; | |
5173 | ||
5174 | return 0; | |
5175 | } | |
5176 | ||
5177 | static void set_last_buddy(struct sched_entity *se) | |
5178 | { | |
5179 | if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) | |
5180 | return; | |
5181 | ||
5182 | for_each_sched_entity(se) | |
5183 | cfs_rq_of(se)->last = se; | |
5184 | } | |
5185 | ||
5186 | static void set_next_buddy(struct sched_entity *se) | |
5187 | { | |
5188 | if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) | |
5189 | return; | |
5190 | ||
5191 | for_each_sched_entity(se) | |
5192 | cfs_rq_of(se)->next = se; | |
5193 | } | |
5194 | ||
5195 | static void set_skip_buddy(struct sched_entity *se) | |
5196 | { | |
5197 | for_each_sched_entity(se) | |
5198 | cfs_rq_of(se)->skip = se; | |
5199 | } | |
5200 | ||
5201 | /* | |
5202 | * Preempt the current task with a newly woken task if needed: | |
5203 | */ | |
5204 | static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) | |
5205 | { | |
5206 | struct task_struct *curr = rq->curr; | |
5207 | struct sched_entity *se = &curr->se, *pse = &p->se; | |
5208 | struct cfs_rq *cfs_rq = task_cfs_rq(curr); | |
5209 | int scale = cfs_rq->nr_running >= sched_nr_latency; | |
5210 | int next_buddy_marked = 0; | |
5211 | ||
5212 | if (unlikely(se == pse)) | |
5213 | return; | |
5214 | ||
5215 | /* | |
5216 | * This is possible from callers such as attach_tasks(), in which we | |
5217 | * unconditionally check_prempt_curr() after an enqueue (which may have | |
5218 | * lead to a throttle). This both saves work and prevents false | |
5219 | * next-buddy nomination below. | |
5220 | */ | |
5221 | if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) | |
5222 | return; | |
5223 | ||
5224 | if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) { | |
5225 | set_next_buddy(pse); | |
5226 | next_buddy_marked = 1; | |
5227 | } | |
5228 | ||
5229 | /* | |
5230 | * We can come here with TIF_NEED_RESCHED already set from new task | |
5231 | * wake up path. | |
5232 | * | |
5233 | * Note: this also catches the edge-case of curr being in a throttled | |
5234 | * group (e.g. via set_curr_task), since update_curr() (in the | |
5235 | * enqueue of curr) will have resulted in resched being set. This | |
5236 | * prevents us from potentially nominating it as a false LAST_BUDDY | |
5237 | * below. | |
5238 | */ | |
5239 | if (test_tsk_need_resched(curr)) | |
5240 | return; | |
5241 | ||
5242 | /* Idle tasks are by definition preempted by non-idle tasks. */ | |
5243 | if (unlikely(curr->policy == SCHED_IDLE) && | |
5244 | likely(p->policy != SCHED_IDLE)) | |
5245 | goto preempt; | |
5246 | ||
5247 | /* | |
5248 | * Batch and idle tasks do not preempt non-idle tasks (their preemption | |
5249 | * is driven by the tick): | |
5250 | */ | |
5251 | if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION)) | |
5252 | return; | |
5253 | ||
5254 | find_matching_se(&se, &pse); | |
5255 | update_curr(cfs_rq_of(se)); | |
5256 | BUG_ON(!pse); | |
5257 | if (wakeup_preempt_entity(se, pse) == 1) { | |
5258 | /* | |
5259 | * Bias pick_next to pick the sched entity that is | |
5260 | * triggering this preemption. | |
5261 | */ | |
5262 | if (!next_buddy_marked) | |
5263 | set_next_buddy(pse); | |
5264 | goto preempt; | |
5265 | } | |
5266 | ||
5267 | return; | |
5268 | ||
5269 | preempt: | |
5270 | resched_curr(rq); | |
5271 | /* | |
5272 | * Only set the backward buddy when the current task is still | |
5273 | * on the rq. This can happen when a wakeup gets interleaved | |
5274 | * with schedule on the ->pre_schedule() or idle_balance() | |
5275 | * point, either of which can * drop the rq lock. | |
5276 | * | |
5277 | * Also, during early boot the idle thread is in the fair class, | |
5278 | * for obvious reasons its a bad idea to schedule back to it. | |
5279 | */ | |
5280 | if (unlikely(!se->on_rq || curr == rq->idle)) | |
5281 | return; | |
5282 | ||
5283 | if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) | |
5284 | set_last_buddy(se); | |
5285 | } | |
5286 | ||
5287 | static struct task_struct * | |
5288 | pick_next_task_fair(struct rq *rq, struct task_struct *prev) | |
5289 | { | |
5290 | struct cfs_rq *cfs_rq = &rq->cfs; | |
5291 | struct sched_entity *se; | |
5292 | struct task_struct *p; | |
5293 | int new_tasks; | |
5294 | ||
5295 | again: | |
5296 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
5297 | if (!cfs_rq->nr_running) | |
5298 | goto idle; | |
5299 | ||
5300 | if (prev->sched_class != &fair_sched_class) | |
5301 | goto simple; | |
5302 | ||
5303 | /* | |
5304 | * Because of the set_next_buddy() in dequeue_task_fair() it is rather | |
5305 | * likely that a next task is from the same cgroup as the current. | |
5306 | * | |
5307 | * Therefore attempt to avoid putting and setting the entire cgroup | |
5308 | * hierarchy, only change the part that actually changes. | |
5309 | */ | |
5310 | ||
5311 | do { | |
5312 | struct sched_entity *curr = cfs_rq->curr; | |
5313 | ||
5314 | /* | |
5315 | * Since we got here without doing put_prev_entity() we also | |
5316 | * have to consider cfs_rq->curr. If it is still a runnable | |
5317 | * entity, update_curr() will update its vruntime, otherwise | |
5318 | * forget we've ever seen it. | |
5319 | */ | |
5320 | if (curr) { | |
5321 | if (curr->on_rq) | |
5322 | update_curr(cfs_rq); | |
5323 | else | |
5324 | curr = NULL; | |
5325 | ||
5326 | /* | |
5327 | * This call to check_cfs_rq_runtime() will do the | |
5328 | * throttle and dequeue its entity in the parent(s). | |
5329 | * Therefore the 'simple' nr_running test will indeed | |
5330 | * be correct. | |
5331 | */ | |
5332 | if (unlikely(check_cfs_rq_runtime(cfs_rq))) | |
5333 | goto simple; | |
5334 | } | |
5335 | ||
5336 | se = pick_next_entity(cfs_rq, curr); | |
5337 | cfs_rq = group_cfs_rq(se); | |
5338 | } while (cfs_rq); | |
5339 | ||
5340 | p = task_of(se); | |
5341 | ||
5342 | /* | |
5343 | * Since we haven't yet done put_prev_entity and if the selected task | |
5344 | * is a different task than we started out with, try and touch the | |
5345 | * least amount of cfs_rqs. | |
5346 | */ | |
5347 | if (prev != p) { | |
5348 | struct sched_entity *pse = &prev->se; | |
5349 | ||
5350 | while (!(cfs_rq = is_same_group(se, pse))) { | |
5351 | int se_depth = se->depth; | |
5352 | int pse_depth = pse->depth; | |
5353 | ||
5354 | if (se_depth <= pse_depth) { | |
5355 | put_prev_entity(cfs_rq_of(pse), pse); | |
5356 | pse = parent_entity(pse); | |
5357 | } | |
5358 | if (se_depth >= pse_depth) { | |
5359 | set_next_entity(cfs_rq_of(se), se); | |
5360 | se = parent_entity(se); | |
5361 | } | |
5362 | } | |
5363 | ||
5364 | put_prev_entity(cfs_rq, pse); | |
5365 | set_next_entity(cfs_rq, se); | |
5366 | } | |
5367 | ||
5368 | if (hrtick_enabled(rq)) | |
5369 | hrtick_start_fair(rq, p); | |
5370 | ||
5371 | return p; | |
5372 | simple: | |
5373 | cfs_rq = &rq->cfs; | |
5374 | #endif | |
5375 | ||
5376 | if (!cfs_rq->nr_running) | |
5377 | goto idle; | |
5378 | ||
5379 | put_prev_task(rq, prev); | |
5380 | ||
5381 | do { | |
5382 | se = pick_next_entity(cfs_rq, NULL); | |
5383 | set_next_entity(cfs_rq, se); | |
5384 | cfs_rq = group_cfs_rq(se); | |
5385 | } while (cfs_rq); | |
5386 | ||
5387 | p = task_of(se); | |
5388 | ||
5389 | if (hrtick_enabled(rq)) | |
5390 | hrtick_start_fair(rq, p); | |
5391 | ||
5392 | return p; | |
5393 | ||
5394 | idle: | |
5395 | new_tasks = idle_balance(rq); | |
5396 | /* | |
5397 | * Because idle_balance() releases (and re-acquires) rq->lock, it is | |
5398 | * possible for any higher priority task to appear. In that case we | |
5399 | * must re-start the pick_next_entity() loop. | |
5400 | */ | |
5401 | if (new_tasks < 0) | |
5402 | return RETRY_TASK; | |
5403 | ||
5404 | if (new_tasks > 0) | |
5405 | goto again; | |
5406 | ||
5407 | return NULL; | |
5408 | } | |
5409 | ||
5410 | /* | |
5411 | * Account for a descheduled task: | |
5412 | */ | |
5413 | static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) | |
5414 | { | |
5415 | struct sched_entity *se = &prev->se; | |
5416 | struct cfs_rq *cfs_rq; | |
5417 | ||
5418 | for_each_sched_entity(se) { | |
5419 | cfs_rq = cfs_rq_of(se); | |
5420 | put_prev_entity(cfs_rq, se); | |
5421 | } | |
5422 | } | |
5423 | ||
5424 | /* | |
5425 | * sched_yield() is very simple | |
5426 | * | |
5427 | * The magic of dealing with the ->skip buddy is in pick_next_entity. | |
5428 | */ | |
5429 | static void yield_task_fair(struct rq *rq) | |
5430 | { | |
5431 | struct task_struct *curr = rq->curr; | |
5432 | struct cfs_rq *cfs_rq = task_cfs_rq(curr); | |
5433 | struct sched_entity *se = &curr->se; | |
5434 | ||
5435 | /* | |
5436 | * Are we the only task in the tree? | |
5437 | */ | |
5438 | if (unlikely(rq->nr_running == 1)) | |
5439 | return; | |
5440 | ||
5441 | clear_buddies(cfs_rq, se); | |
5442 | ||
5443 | if (curr->policy != SCHED_BATCH) { | |
5444 | update_rq_clock(rq); | |
5445 | /* | |
5446 | * Update run-time statistics of the 'current'. | |
5447 | */ | |
5448 | update_curr(cfs_rq); | |
5449 | /* | |
5450 | * Tell update_rq_clock() that we've just updated, | |
5451 | * so we don't do microscopic update in schedule() | |
5452 | * and double the fastpath cost. | |
5453 | */ | |
5454 | rq_clock_skip_update(rq, true); | |
5455 | } | |
5456 | ||
5457 | set_skip_buddy(se); | |
5458 | } | |
5459 | ||
5460 | static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) | |
5461 | { | |
5462 | struct sched_entity *se = &p->se; | |
5463 | ||
5464 | /* throttled hierarchies are not runnable */ | |
5465 | if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) | |
5466 | return false; | |
5467 | ||
5468 | /* Tell the scheduler that we'd really like pse to run next. */ | |
5469 | set_next_buddy(se); | |
5470 | ||
5471 | yield_task_fair(rq); | |
5472 | ||
5473 | return true; | |
5474 | } | |
5475 | ||
5476 | #ifdef CONFIG_SMP | |
5477 | /************************************************** | |
5478 | * Fair scheduling class load-balancing methods. | |
5479 | * | |
5480 | * BASICS | |
5481 | * | |
5482 | * The purpose of load-balancing is to achieve the same basic fairness the | |
5483 | * per-cpu scheduler provides, namely provide a proportional amount of compute | |
5484 | * time to each task. This is expressed in the following equation: | |
5485 | * | |
5486 | * W_i,n/P_i == W_j,n/P_j for all i,j (1) | |
5487 | * | |
5488 | * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight | |
5489 | * W_i,0 is defined as: | |
5490 | * | |
5491 | * W_i,0 = \Sum_j w_i,j (2) | |
5492 | * | |
5493 | * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight | |
5494 | * is derived from the nice value as per prio_to_weight[]. | |
5495 | * | |
5496 | * The weight average is an exponential decay average of the instantaneous | |
5497 | * weight: | |
5498 | * | |
5499 | * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3) | |
5500 | * | |
5501 | * C_i is the compute capacity of cpu i, typically it is the | |
5502 | * fraction of 'recent' time available for SCHED_OTHER task execution. But it | |
5503 | * can also include other factors [XXX]. | |
5504 | * | |
5505 | * To achieve this balance we define a measure of imbalance which follows | |
5506 | * directly from (1): | |
5507 | * | |
5508 | * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4) | |
5509 | * | |
5510 | * We them move tasks around to minimize the imbalance. In the continuous | |
5511 | * function space it is obvious this converges, in the discrete case we get | |
5512 | * a few fun cases generally called infeasible weight scenarios. | |
5513 | * | |
5514 | * [XXX expand on: | |
5515 | * - infeasible weights; | |
5516 | * - local vs global optima in the discrete case. ] | |
5517 | * | |
5518 | * | |
5519 | * SCHED DOMAINS | |
5520 | * | |
5521 | * In order to solve the imbalance equation (4), and avoid the obvious O(n^2) | |
5522 | * for all i,j solution, we create a tree of cpus that follows the hardware | |
5523 | * topology where each level pairs two lower groups (or better). This results | |
5524 | * in O(log n) layers. Furthermore we reduce the number of cpus going up the | |
5525 | * tree to only the first of the previous level and we decrease the frequency | |
5526 | * of load-balance at each level inv. proportional to the number of cpus in | |
5527 | * the groups. | |
5528 | * | |
5529 | * This yields: | |
5530 | * | |
5531 | * log_2 n 1 n | |
5532 | * \Sum { --- * --- * 2^i } = O(n) (5) | |
5533 | * i = 0 2^i 2^i | |
5534 | * `- size of each group | |
5535 | * | | `- number of cpus doing load-balance | |
5536 | * | `- freq | |
5537 | * `- sum over all levels | |
5538 | * | |
5539 | * Coupled with a limit on how many tasks we can migrate every balance pass, | |
5540 | * this makes (5) the runtime complexity of the balancer. | |
5541 | * | |
5542 | * An important property here is that each CPU is still (indirectly) connected | |
5543 | * to every other cpu in at most O(log n) steps: | |
5544 | * | |
5545 | * The adjacency matrix of the resulting graph is given by: | |
5546 | * | |
5547 | * log_2 n | |
5548 | * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6) | |
5549 | * k = 0 | |
5550 | * | |
5551 | * And you'll find that: | |
5552 | * | |
5553 | * A^(log_2 n)_i,j != 0 for all i,j (7) | |
5554 | * | |
5555 | * Showing there's indeed a path between every cpu in at most O(log n) steps. | |
5556 | * The task movement gives a factor of O(m), giving a convergence complexity | |
5557 | * of: | |
5558 | * | |
5559 | * O(nm log n), n := nr_cpus, m := nr_tasks (8) | |
5560 | * | |
5561 | * | |
5562 | * WORK CONSERVING | |
5563 | * | |
5564 | * In order to avoid CPUs going idle while there's still work to do, new idle | |
5565 | * balancing is more aggressive and has the newly idle cpu iterate up the domain | |
5566 | * tree itself instead of relying on other CPUs to bring it work. | |
5567 | * | |
5568 | * This adds some complexity to both (5) and (8) but it reduces the total idle | |
5569 | * time. | |
5570 | * | |
5571 | * [XXX more?] | |
5572 | * | |
5573 | * | |
5574 | * CGROUPS | |
5575 | * | |
5576 | * Cgroups make a horror show out of (2), instead of a simple sum we get: | |
5577 | * | |
5578 | * s_k,i | |
5579 | * W_i,0 = \Sum_j \Prod_k w_k * ----- (9) | |
5580 | * S_k | |
5581 | * | |
5582 | * Where | |
5583 | * | |
5584 | * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10) | |
5585 | * | |
5586 | * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i. | |
5587 | * | |
5588 | * The big problem is S_k, its a global sum needed to compute a local (W_i) | |
5589 | * property. | |
5590 | * | |
5591 | * [XXX write more on how we solve this.. _after_ merging pjt's patches that | |
5592 | * rewrite all of this once again.] | |
5593 | */ | |
5594 | ||
5595 | static unsigned long __read_mostly max_load_balance_interval = HZ/10; | |
5596 | ||
5597 | enum fbq_type { regular, remote, all }; | |
5598 | ||
5599 | #define LBF_ALL_PINNED 0x01 | |
5600 | #define LBF_NEED_BREAK 0x02 | |
5601 | #define LBF_DST_PINNED 0x04 | |
5602 | #define LBF_SOME_PINNED 0x08 | |
5603 | ||
5604 | struct lb_env { | |
5605 | struct sched_domain *sd; | |
5606 | ||
5607 | struct rq *src_rq; | |
5608 | int src_cpu; | |
5609 | ||
5610 | int dst_cpu; | |
5611 | struct rq *dst_rq; | |
5612 | ||
5613 | struct cpumask *dst_grpmask; | |
5614 | int new_dst_cpu; | |
5615 | enum cpu_idle_type idle; | |
5616 | long imbalance; | |
5617 | /* The set of CPUs under consideration for load-balancing */ | |
5618 | struct cpumask *cpus; | |
5619 | ||
5620 | unsigned int flags; | |
5621 | ||
5622 | unsigned int loop; | |
5623 | unsigned int loop_break; | |
5624 | unsigned int loop_max; | |
5625 | ||
5626 | enum fbq_type fbq_type; | |
5627 | struct list_head tasks; | |
5628 | }; | |
5629 | ||
5630 | /* | |
5631 | * Is this task likely cache-hot: | |
5632 | */ | |
5633 | static int task_hot(struct task_struct *p, struct lb_env *env) | |
5634 | { | |
5635 | s64 delta; | |
5636 | ||
5637 | lockdep_assert_held(&env->src_rq->lock); | |
5638 | ||
5639 | if (p->sched_class != &fair_sched_class) | |
5640 | return 0; | |
5641 | ||
5642 | if (unlikely(p->policy == SCHED_IDLE)) | |
5643 | return 0; | |
5644 | ||
5645 | /* | |
5646 | * Buddy candidates are cache hot: | |
5647 | */ | |
5648 | if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running && | |
5649 | (&p->se == cfs_rq_of(&p->se)->next || | |
5650 | &p->se == cfs_rq_of(&p->se)->last)) | |
5651 | return 1; | |
5652 | ||
5653 | if (sysctl_sched_migration_cost == -1) | |
5654 | return 1; | |
5655 | if (sysctl_sched_migration_cost == 0) | |
5656 | return 0; | |
5657 | ||
5658 | delta = rq_clock_task(env->src_rq) - p->se.exec_start; | |
5659 | ||
5660 | return delta < (s64)sysctl_sched_migration_cost; | |
5661 | } | |
5662 | ||
5663 | #ifdef CONFIG_NUMA_BALANCING | |
5664 | /* | |
5665 | * Returns true if the destination node is the preferred node. | |
5666 | * Needs to match fbq_classify_rq(): if there is a runnable task | |
5667 | * that is not on its preferred node, we should identify it. | |
5668 | */ | |
5669 | static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env) | |
5670 | { | |
5671 | struct numa_group *numa_group = rcu_dereference(p->numa_group); | |
5672 | unsigned long src_faults, dst_faults; | |
5673 | int src_nid, dst_nid; | |
5674 | ||
5675 | if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults || | |
5676 | !(env->sd->flags & SD_NUMA)) { | |
5677 | return false; | |
5678 | } | |
5679 | ||
5680 | src_nid = cpu_to_node(env->src_cpu); | |
5681 | dst_nid = cpu_to_node(env->dst_cpu); | |
5682 | ||
5683 | if (src_nid == dst_nid) | |
5684 | return false; | |
5685 | ||
5686 | /* Encourage migration to the preferred node. */ | |
5687 | if (dst_nid == p->numa_preferred_nid) | |
5688 | return true; | |
5689 | ||
5690 | /* Migrating away from the preferred node is bad. */ | |
5691 | if (src_nid == p->numa_preferred_nid) | |
5692 | return false; | |
5693 | ||
5694 | if (numa_group) { | |
5695 | src_faults = group_faults(p, src_nid); | |
5696 | dst_faults = group_faults(p, dst_nid); | |
5697 | } else { | |
5698 | src_faults = task_faults(p, src_nid); | |
5699 | dst_faults = task_faults(p, dst_nid); | |
5700 | } | |
5701 | ||
5702 | return dst_faults > src_faults; | |
5703 | } | |
5704 | ||
5705 | ||
5706 | static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env) | |
5707 | { | |
5708 | struct numa_group *numa_group = rcu_dereference(p->numa_group); | |
5709 | unsigned long src_faults, dst_faults; | |
5710 | int src_nid, dst_nid; | |
5711 | ||
5712 | if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER)) | |
5713 | return false; | |
5714 | ||
5715 | if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) | |
5716 | return false; | |
5717 | ||
5718 | src_nid = cpu_to_node(env->src_cpu); | |
5719 | dst_nid = cpu_to_node(env->dst_cpu); | |
5720 | ||
5721 | if (src_nid == dst_nid) | |
5722 | return false; | |
5723 | ||
5724 | /* Migrating away from the preferred node is bad. */ | |
5725 | if (src_nid == p->numa_preferred_nid) | |
5726 | return true; | |
5727 | ||
5728 | /* Encourage migration to the preferred node. */ | |
5729 | if (dst_nid == p->numa_preferred_nid) | |
5730 | return false; | |
5731 | ||
5732 | if (numa_group) { | |
5733 | src_faults = group_faults(p, src_nid); | |
5734 | dst_faults = group_faults(p, dst_nid); | |
5735 | } else { | |
5736 | src_faults = task_faults(p, src_nid); | |
5737 | dst_faults = task_faults(p, dst_nid); | |
5738 | } | |
5739 | ||
5740 | return dst_faults < src_faults; | |
5741 | } | |
5742 | ||
5743 | #else | |
5744 | static inline bool migrate_improves_locality(struct task_struct *p, | |
5745 | struct lb_env *env) | |
5746 | { | |
5747 | return false; | |
5748 | } | |
5749 | ||
5750 | static inline bool migrate_degrades_locality(struct task_struct *p, | |
5751 | struct lb_env *env) | |
5752 | { | |
5753 | return false; | |
5754 | } | |
5755 | #endif | |
5756 | ||
5757 | /* | |
5758 | * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? | |
5759 | */ | |
5760 | static | |
5761 | int can_migrate_task(struct task_struct *p, struct lb_env *env) | |
5762 | { | |
5763 | int tsk_cache_hot = 0; | |
5764 | ||
5765 | lockdep_assert_held(&env->src_rq->lock); | |
5766 | ||
5767 | /* | |
5768 | * We do not migrate tasks that are: | |
5769 | * 1) throttled_lb_pair, or | |
5770 | * 2) cannot be migrated to this CPU due to cpus_allowed, or | |
5771 | * 3) running (obviously), or | |
5772 | * 4) are cache-hot on their current CPU. | |
5773 | */ | |
5774 | if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) | |
5775 | return 0; | |
5776 | ||
5777 | if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) { | |
5778 | int cpu; | |
5779 | ||
5780 | schedstat_inc(p, se.statistics.nr_failed_migrations_affine); | |
5781 | ||
5782 | env->flags |= LBF_SOME_PINNED; | |
5783 | ||
5784 | /* | |
5785 | * Remember if this task can be migrated to any other cpu in | |
5786 | * our sched_group. We may want to revisit it if we couldn't | |
5787 | * meet load balance goals by pulling other tasks on src_cpu. | |
5788 | * | |
5789 | * Also avoid computing new_dst_cpu if we have already computed | |
5790 | * one in current iteration. | |
5791 | */ | |
5792 | if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED)) | |
5793 | return 0; | |
5794 | ||
5795 | /* Prevent to re-select dst_cpu via env's cpus */ | |
5796 | for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) { | |
5797 | if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) { | |
5798 | env->flags |= LBF_DST_PINNED; | |
5799 | env->new_dst_cpu = cpu; | |
5800 | break; | |
5801 | } | |
5802 | } | |
5803 | ||
5804 | return 0; | |
5805 | } | |
5806 | ||
5807 | /* Record that we found atleast one task that could run on dst_cpu */ | |
5808 | env->flags &= ~LBF_ALL_PINNED; | |
5809 | ||
5810 | if (task_running(env->src_rq, p)) { | |
5811 | schedstat_inc(p, se.statistics.nr_failed_migrations_running); | |
5812 | return 0; | |
5813 | } | |
5814 | ||
5815 | /* | |
5816 | * Aggressive migration if: | |
5817 | * 1) destination numa is preferred | |
5818 | * 2) task is cache cold, or | |
5819 | * 3) too many balance attempts have failed. | |
5820 | */ | |
5821 | tsk_cache_hot = task_hot(p, env); | |
5822 | if (!tsk_cache_hot) | |
5823 | tsk_cache_hot = migrate_degrades_locality(p, env); | |
5824 | ||
5825 | if (migrate_improves_locality(p, env) || !tsk_cache_hot || | |
5826 | env->sd->nr_balance_failed > env->sd->cache_nice_tries) { | |
5827 | if (tsk_cache_hot) { | |
5828 | schedstat_inc(env->sd, lb_hot_gained[env->idle]); | |
5829 | schedstat_inc(p, se.statistics.nr_forced_migrations); | |
5830 | } | |
5831 | return 1; | |
5832 | } | |
5833 | ||
5834 | schedstat_inc(p, se.statistics.nr_failed_migrations_hot); | |
5835 | return 0; | |
5836 | } | |
5837 | ||
5838 | /* | |
5839 | * detach_task() -- detach the task for the migration specified in env | |
5840 | */ | |
5841 | static void detach_task(struct task_struct *p, struct lb_env *env) | |
5842 | { | |
5843 | lockdep_assert_held(&env->src_rq->lock); | |
5844 | ||
5845 | deactivate_task(env->src_rq, p, 0); | |
5846 | p->on_rq = TASK_ON_RQ_MIGRATING; | |
5847 | set_task_cpu(p, env->dst_cpu); | |
5848 | } | |
5849 | ||
5850 | /* | |
5851 | * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as | |
5852 | * part of active balancing operations within "domain". | |
5853 | * | |
5854 | * Returns a task if successful and NULL otherwise. | |
5855 | */ | |
5856 | static struct task_struct *detach_one_task(struct lb_env *env) | |
5857 | { | |
5858 | struct task_struct *p, *n; | |
5859 | ||
5860 | lockdep_assert_held(&env->src_rq->lock); | |
5861 | ||
5862 | list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) { | |
5863 | if (!can_migrate_task(p, env)) | |
5864 | continue; | |
5865 | ||
5866 | detach_task(p, env); | |
5867 | ||
5868 | /* | |
5869 | * Right now, this is only the second place where | |
5870 | * lb_gained[env->idle] is updated (other is detach_tasks) | |
5871 | * so we can safely collect stats here rather than | |
5872 | * inside detach_tasks(). | |
5873 | */ | |
5874 | schedstat_inc(env->sd, lb_gained[env->idle]); | |
5875 | return p; | |
5876 | } | |
5877 | return NULL; | |
5878 | } | |
5879 | ||
5880 | static const unsigned int sched_nr_migrate_break = 32; | |
5881 | ||
5882 | /* | |
5883 | * detach_tasks() -- tries to detach up to imbalance weighted load from | |
5884 | * busiest_rq, as part of a balancing operation within domain "sd". | |
5885 | * | |
5886 | * Returns number of detached tasks if successful and 0 otherwise. | |
5887 | */ | |
5888 | static int detach_tasks(struct lb_env *env) | |
5889 | { | |
5890 | struct list_head *tasks = &env->src_rq->cfs_tasks; | |
5891 | struct task_struct *p; | |
5892 | unsigned long load; | |
5893 | int detached = 0; | |
5894 | ||
5895 | lockdep_assert_held(&env->src_rq->lock); | |
5896 | ||
5897 | if (env->imbalance <= 0) | |
5898 | return 0; | |
5899 | ||
5900 | while (!list_empty(tasks)) { | |
5901 | p = list_first_entry(tasks, struct task_struct, se.group_node); | |
5902 | ||
5903 | env->loop++; | |
5904 | /* We've more or less seen every task there is, call it quits */ | |
5905 | if (env->loop > env->loop_max) | |
5906 | break; | |
5907 | ||
5908 | /* take a breather every nr_migrate tasks */ | |
5909 | if (env->loop > env->loop_break) { | |
5910 | env->loop_break += sched_nr_migrate_break; | |
5911 | env->flags |= LBF_NEED_BREAK; | |
5912 | break; | |
5913 | } | |
5914 | ||
5915 | if (!can_migrate_task(p, env)) | |
5916 | goto next; | |
5917 | ||
5918 | load = task_h_load(p); | |
5919 | ||
5920 | if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) | |
5921 | goto next; | |
5922 | ||
5923 | if ((load / 2) > env->imbalance) | |
5924 | goto next; | |
5925 | ||
5926 | detach_task(p, env); | |
5927 | list_add(&p->se.group_node, &env->tasks); | |
5928 | ||
5929 | detached++; | |
5930 | env->imbalance -= load; | |
5931 | ||
5932 | #ifdef CONFIG_PREEMPT | |
5933 | /* | |
5934 | * NEWIDLE balancing is a source of latency, so preemptible | |
5935 | * kernels will stop after the first task is detached to minimize | |
5936 | * the critical section. | |
5937 | */ | |
5938 | if (env->idle == CPU_NEWLY_IDLE) | |
5939 | break; | |
5940 | #endif | |
5941 | ||
5942 | /* | |
5943 | * We only want to steal up to the prescribed amount of | |
5944 | * weighted load. | |
5945 | */ | |
5946 | if (env->imbalance <= 0) | |
5947 | break; | |
5948 | ||
5949 | continue; | |
5950 | next: | |
5951 | list_move_tail(&p->se.group_node, tasks); | |
5952 | } | |
5953 | ||
5954 | /* | |
5955 | * Right now, this is one of only two places we collect this stat | |
5956 | * so we can safely collect detach_one_task() stats here rather | |
5957 | * than inside detach_one_task(). | |
5958 | */ | |
5959 | schedstat_add(env->sd, lb_gained[env->idle], detached); | |
5960 | ||
5961 | return detached; | |
5962 | } | |
5963 | ||
5964 | /* | |
5965 | * attach_task() -- attach the task detached by detach_task() to its new rq. | |
5966 | */ | |
5967 | static void attach_task(struct rq *rq, struct task_struct *p) | |
5968 | { | |
5969 | lockdep_assert_held(&rq->lock); | |
5970 | ||
5971 | BUG_ON(task_rq(p) != rq); | |
5972 | p->on_rq = TASK_ON_RQ_QUEUED; | |
5973 | activate_task(rq, p, 0); | |
5974 | check_preempt_curr(rq, p, 0); | |
5975 | } | |
5976 | ||
5977 | /* | |
5978 | * attach_one_task() -- attaches the task returned from detach_one_task() to | |
5979 | * its new rq. | |
5980 | */ | |
5981 | static void attach_one_task(struct rq *rq, struct task_struct *p) | |
5982 | { | |
5983 | raw_spin_lock(&rq->lock); | |
5984 | attach_task(rq, p); | |
5985 | raw_spin_unlock(&rq->lock); | |
5986 | } | |
5987 | ||
5988 | /* | |
5989 | * attach_tasks() -- attaches all tasks detached by detach_tasks() to their | |
5990 | * new rq. | |
5991 | */ | |
5992 | static void attach_tasks(struct lb_env *env) | |
5993 | { | |
5994 | struct list_head *tasks = &env->tasks; | |
5995 | struct task_struct *p; | |
5996 | ||
5997 | raw_spin_lock(&env->dst_rq->lock); | |
5998 | ||
5999 | while (!list_empty(tasks)) { | |
6000 | p = list_first_entry(tasks, struct task_struct, se.group_node); | |
6001 | list_del_init(&p->se.group_node); | |
6002 | ||
6003 | attach_task(env->dst_rq, p); | |
6004 | } | |
6005 | ||
6006 | raw_spin_unlock(&env->dst_rq->lock); | |
6007 | } | |
6008 | ||
6009 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
6010 | /* | |
6011 | * update tg->load_weight by folding this cpu's load_avg | |
6012 | */ | |
6013 | static void __update_blocked_averages_cpu(struct task_group *tg, int cpu) | |
6014 | { | |
6015 | struct sched_entity *se = tg->se[cpu]; | |
6016 | struct cfs_rq *cfs_rq = tg->cfs_rq[cpu]; | |
6017 | ||
6018 | /* throttled entities do not contribute to load */ | |
6019 | if (throttled_hierarchy(cfs_rq)) | |
6020 | return; | |
6021 | ||
6022 | update_cfs_rq_blocked_load(cfs_rq, 1); | |
6023 | ||
6024 | if (se) { | |
6025 | update_entity_load_avg(se, 1); | |
6026 | /* | |
6027 | * We pivot on our runnable average having decayed to zero for | |
6028 | * list removal. This generally implies that all our children | |
6029 | * have also been removed (modulo rounding error or bandwidth | |
6030 | * control); however, such cases are rare and we can fix these | |
6031 | * at enqueue. | |
6032 | * | |
6033 | * TODO: fix up out-of-order children on enqueue. | |
6034 | */ | |
6035 | if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running) | |
6036 | list_del_leaf_cfs_rq(cfs_rq); | |
6037 | } else { | |
6038 | struct rq *rq = rq_of(cfs_rq); | |
6039 | update_rq_runnable_avg(rq, rq->nr_running); | |
6040 | } | |
6041 | } | |
6042 | ||
6043 | static void update_blocked_averages(int cpu) | |
6044 | { | |
6045 | struct rq *rq = cpu_rq(cpu); | |
6046 | struct cfs_rq *cfs_rq; | |
6047 | unsigned long flags; | |
6048 | ||
6049 | raw_spin_lock_irqsave(&rq->lock, flags); | |
6050 | update_rq_clock(rq); | |
6051 | /* | |
6052 | * Iterates the task_group tree in a bottom up fashion, see | |
6053 | * list_add_leaf_cfs_rq() for details. | |
6054 | */ | |
6055 | for_each_leaf_cfs_rq(rq, cfs_rq) { | |
6056 | /* | |
6057 | * Note: We may want to consider periodically releasing | |
6058 | * rq->lock about these updates so that creating many task | |
6059 | * groups does not result in continually extending hold time. | |
6060 | */ | |
6061 | __update_blocked_averages_cpu(cfs_rq->tg, rq->cpu); | |
6062 | } | |
6063 | ||
6064 | raw_spin_unlock_irqrestore(&rq->lock, flags); | |
6065 | } | |
6066 | ||
6067 | /* | |
6068 | * Compute the hierarchical load factor for cfs_rq and all its ascendants. | |
6069 | * This needs to be done in a top-down fashion because the load of a child | |
6070 | * group is a fraction of its parents load. | |
6071 | */ | |
6072 | static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) | |
6073 | { | |
6074 | struct rq *rq = rq_of(cfs_rq); | |
6075 | struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)]; | |
6076 | unsigned long now = jiffies; | |
6077 | unsigned long load; | |
6078 | ||
6079 | if (cfs_rq->last_h_load_update == now) | |
6080 | return; | |
6081 | ||
6082 | cfs_rq->h_load_next = NULL; | |
6083 | for_each_sched_entity(se) { | |
6084 | cfs_rq = cfs_rq_of(se); | |
6085 | cfs_rq->h_load_next = se; | |
6086 | if (cfs_rq->last_h_load_update == now) | |
6087 | break; | |
6088 | } | |
6089 | ||
6090 | if (!se) { | |
6091 | cfs_rq->h_load = cfs_rq->runnable_load_avg; | |
6092 | cfs_rq->last_h_load_update = now; | |
6093 | } | |
6094 | ||
6095 | while ((se = cfs_rq->h_load_next) != NULL) { | |
6096 | load = cfs_rq->h_load; | |
6097 | load = div64_ul(load * se->avg.load_avg_contrib, | |
6098 | cfs_rq->runnable_load_avg + 1); | |
6099 | cfs_rq = group_cfs_rq(se); | |
6100 | cfs_rq->h_load = load; | |
6101 | cfs_rq->last_h_load_update = now; | |
6102 | } | |
6103 | } | |
6104 | ||
6105 | static unsigned long task_h_load(struct task_struct *p) | |
6106 | { | |
6107 | struct cfs_rq *cfs_rq = task_cfs_rq(p); | |
6108 | ||
6109 | update_cfs_rq_h_load(cfs_rq); | |
6110 | return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load, | |
6111 | cfs_rq->runnable_load_avg + 1); | |
6112 | } | |
6113 | #else | |
6114 | static inline void update_blocked_averages(int cpu) | |
6115 | { | |
6116 | } | |
6117 | ||
6118 | static unsigned long task_h_load(struct task_struct *p) | |
6119 | { | |
6120 | return p->se.avg.load_avg_contrib; | |
6121 | } | |
6122 | #endif | |
6123 | ||
6124 | /********** Helpers for find_busiest_group ************************/ | |
6125 | ||
6126 | enum group_type { | |
6127 | group_other = 0, | |
6128 | group_imbalanced, | |
6129 | group_overloaded, | |
6130 | }; | |
6131 | ||
6132 | /* | |
6133 | * sg_lb_stats - stats of a sched_group required for load_balancing | |
6134 | */ | |
6135 | struct sg_lb_stats { | |
6136 | unsigned long avg_load; /*Avg load across the CPUs of the group */ | |
6137 | unsigned long group_load; /* Total load over the CPUs of the group */ | |
6138 | unsigned long sum_weighted_load; /* Weighted load of group's tasks */ | |
6139 | unsigned long load_per_task; | |
6140 | unsigned long group_capacity; | |
6141 | unsigned long group_usage; /* Total usage of the group */ | |
6142 | unsigned int sum_nr_running; /* Nr tasks running in the group */ | |
6143 | unsigned int idle_cpus; | |
6144 | unsigned int group_weight; | |
6145 | enum group_type group_type; | |
6146 | int group_no_capacity; | |
6147 | #ifdef CONFIG_NUMA_BALANCING | |
6148 | unsigned int nr_numa_running; | |
6149 | unsigned int nr_preferred_running; | |
6150 | #endif | |
6151 | }; | |
6152 | ||
6153 | /* | |
6154 | * sd_lb_stats - Structure to store the statistics of a sched_domain | |
6155 | * during load balancing. | |
6156 | */ | |
6157 | struct sd_lb_stats { | |
6158 | struct sched_group *busiest; /* Busiest group in this sd */ | |
6159 | struct sched_group *local; /* Local group in this sd */ | |
6160 | unsigned long total_load; /* Total load of all groups in sd */ | |
6161 | unsigned long total_capacity; /* Total capacity of all groups in sd */ | |
6162 | unsigned long avg_load; /* Average load across all groups in sd */ | |
6163 | ||
6164 | struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ | |
6165 | struct sg_lb_stats local_stat; /* Statistics of the local group */ | |
6166 | }; | |
6167 | ||
6168 | static inline void init_sd_lb_stats(struct sd_lb_stats *sds) | |
6169 | { | |
6170 | /* | |
6171 | * Skimp on the clearing to avoid duplicate work. We can avoid clearing | |
6172 | * local_stat because update_sg_lb_stats() does a full clear/assignment. | |
6173 | * We must however clear busiest_stat::avg_load because | |
6174 | * update_sd_pick_busiest() reads this before assignment. | |
6175 | */ | |
6176 | *sds = (struct sd_lb_stats){ | |
6177 | .busiest = NULL, | |
6178 | .local = NULL, | |
6179 | .total_load = 0UL, | |
6180 | .total_capacity = 0UL, | |
6181 | .busiest_stat = { | |
6182 | .avg_load = 0UL, | |
6183 | .sum_nr_running = 0, | |
6184 | .group_type = group_other, | |
6185 | }, | |
6186 | }; | |
6187 | } | |
6188 | ||
6189 | /** | |
6190 | * get_sd_load_idx - Obtain the load index for a given sched domain. | |
6191 | * @sd: The sched_domain whose load_idx is to be obtained. | |
6192 | * @idle: The idle status of the CPU for whose sd load_idx is obtained. | |
6193 | * | |
6194 | * Return: The load index. | |
6195 | */ | |
6196 | static inline int get_sd_load_idx(struct sched_domain *sd, | |
6197 | enum cpu_idle_type idle) | |
6198 | { | |
6199 | int load_idx; | |
6200 | ||
6201 | switch (idle) { | |
6202 | case CPU_NOT_IDLE: | |
6203 | load_idx = sd->busy_idx; | |
6204 | break; | |
6205 | ||
6206 | case CPU_NEWLY_IDLE: | |
6207 | load_idx = sd->newidle_idx; | |
6208 | break; | |
6209 | default: | |
6210 | load_idx = sd->idle_idx; | |
6211 | break; | |
6212 | } | |
6213 | ||
6214 | return load_idx; | |
6215 | } | |
6216 | ||
6217 | static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu) | |
6218 | { | |
6219 | if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1)) | |
6220 | return sd->smt_gain / sd->span_weight; | |
6221 | ||
6222 | return SCHED_CAPACITY_SCALE; | |
6223 | } | |
6224 | ||
6225 | unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu) | |
6226 | { | |
6227 | return default_scale_cpu_capacity(sd, cpu); | |
6228 | } | |
6229 | ||
6230 | static unsigned long scale_rt_capacity(int cpu) | |
6231 | { | |
6232 | struct rq *rq = cpu_rq(cpu); | |
6233 | u64 total, used, age_stamp, avg; | |
6234 | s64 delta; | |
6235 | ||
6236 | /* | |
6237 | * Since we're reading these variables without serialization make sure | |
6238 | * we read them once before doing sanity checks on them. | |
6239 | */ | |
6240 | age_stamp = READ_ONCE(rq->age_stamp); | |
6241 | avg = READ_ONCE(rq->rt_avg); | |
6242 | delta = __rq_clock_broken(rq) - age_stamp; | |
6243 | ||
6244 | if (unlikely(delta < 0)) | |
6245 | delta = 0; | |
6246 | ||
6247 | total = sched_avg_period() + delta; | |
6248 | ||
6249 | used = div_u64(avg, total); | |
6250 | ||
6251 | if (likely(used < SCHED_CAPACITY_SCALE)) | |
6252 | return SCHED_CAPACITY_SCALE - used; | |
6253 | ||
6254 | return 1; | |
6255 | } | |
6256 | ||
6257 | static void update_cpu_capacity(struct sched_domain *sd, int cpu) | |
6258 | { | |
6259 | unsigned long capacity = SCHED_CAPACITY_SCALE; | |
6260 | struct sched_group *sdg = sd->groups; | |
6261 | ||
6262 | if (sched_feat(ARCH_CAPACITY)) | |
6263 | capacity *= arch_scale_cpu_capacity(sd, cpu); | |
6264 | else | |
6265 | capacity *= default_scale_cpu_capacity(sd, cpu); | |
6266 | ||
6267 | capacity >>= SCHED_CAPACITY_SHIFT; | |
6268 | ||
6269 | cpu_rq(cpu)->cpu_capacity_orig = capacity; | |
6270 | ||
6271 | capacity *= scale_rt_capacity(cpu); | |
6272 | capacity >>= SCHED_CAPACITY_SHIFT; | |
6273 | ||
6274 | if (!capacity) | |
6275 | capacity = 1; | |
6276 | ||
6277 | cpu_rq(cpu)->cpu_capacity = capacity; | |
6278 | sdg->sgc->capacity = capacity; | |
6279 | } | |
6280 | ||
6281 | void update_group_capacity(struct sched_domain *sd, int cpu) | |
6282 | { | |
6283 | struct sched_domain *child = sd->child; | |
6284 | struct sched_group *group, *sdg = sd->groups; | |
6285 | unsigned long capacity; | |
6286 | unsigned long interval; | |
6287 | ||
6288 | interval = msecs_to_jiffies(sd->balance_interval); | |
6289 | interval = clamp(interval, 1UL, max_load_balance_interval); | |
6290 | sdg->sgc->next_update = jiffies + interval; | |
6291 | ||
6292 | if (!child) { | |
6293 | update_cpu_capacity(sd, cpu); | |
6294 | return; | |
6295 | } | |
6296 | ||
6297 | capacity = 0; | |
6298 | ||
6299 | if (child->flags & SD_OVERLAP) { | |
6300 | /* | |
6301 | * SD_OVERLAP domains cannot assume that child groups | |
6302 | * span the current group. | |
6303 | */ | |
6304 | ||
6305 | for_each_cpu(cpu, sched_group_cpus(sdg)) { | |
6306 | struct sched_group_capacity *sgc; | |
6307 | struct rq *rq = cpu_rq(cpu); | |
6308 | ||
6309 | /* | |
6310 | * build_sched_domains() -> init_sched_groups_capacity() | |
6311 | * gets here before we've attached the domains to the | |
6312 | * runqueues. | |
6313 | * | |
6314 | * Use capacity_of(), which is set irrespective of domains | |
6315 | * in update_cpu_capacity(). | |
6316 | * | |
6317 | * This avoids capacity from being 0 and | |
6318 | * causing divide-by-zero issues on boot. | |
6319 | */ | |
6320 | if (unlikely(!rq->sd)) { | |
6321 | capacity += capacity_of(cpu); | |
6322 | continue; | |
6323 | } | |
6324 | ||
6325 | sgc = rq->sd->groups->sgc; | |
6326 | capacity += sgc->capacity; | |
6327 | } | |
6328 | } else { | |
6329 | /* | |
6330 | * !SD_OVERLAP domains can assume that child groups | |
6331 | * span the current group. | |
6332 | */ | |
6333 | ||
6334 | group = child->groups; | |
6335 | do { | |
6336 | capacity += group->sgc->capacity; | |
6337 | group = group->next; | |
6338 | } while (group != child->groups); | |
6339 | } | |
6340 | ||
6341 | sdg->sgc->capacity = capacity; | |
6342 | } | |
6343 | ||
6344 | /* | |
6345 | * Check whether the capacity of the rq has been noticeably reduced by side | |
6346 | * activity. The imbalance_pct is used for the threshold. | |
6347 | * Return true is the capacity is reduced | |
6348 | */ | |
6349 | static inline int | |
6350 | check_cpu_capacity(struct rq *rq, struct sched_domain *sd) | |
6351 | { | |
6352 | return ((rq->cpu_capacity * sd->imbalance_pct) < | |
6353 | (rq->cpu_capacity_orig * 100)); | |
6354 | } | |
6355 | ||
6356 | /* | |
6357 | * Group imbalance indicates (and tries to solve) the problem where balancing | |
6358 | * groups is inadequate due to tsk_cpus_allowed() constraints. | |
6359 | * | |
6360 | * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a | |
6361 | * cpumask covering 1 cpu of the first group and 3 cpus of the second group. | |
6362 | * Something like: | |
6363 | * | |
6364 | * { 0 1 2 3 } { 4 5 6 7 } | |
6365 | * * * * * | |
6366 | * | |
6367 | * If we were to balance group-wise we'd place two tasks in the first group and | |
6368 | * two tasks in the second group. Clearly this is undesired as it will overload | |
6369 | * cpu 3 and leave one of the cpus in the second group unused. | |
6370 | * | |
6371 | * The current solution to this issue is detecting the skew in the first group | |
6372 | * by noticing the lower domain failed to reach balance and had difficulty | |
6373 | * moving tasks due to affinity constraints. | |
6374 | * | |
6375 | * When this is so detected; this group becomes a candidate for busiest; see | |
6376 | * update_sd_pick_busiest(). And calculate_imbalance() and | |
6377 | * find_busiest_group() avoid some of the usual balance conditions to allow it | |
6378 | * to create an effective group imbalance. | |
6379 | * | |
6380 | * This is a somewhat tricky proposition since the next run might not find the | |
6381 | * group imbalance and decide the groups need to be balanced again. A most | |
6382 | * subtle and fragile situation. | |
6383 | */ | |
6384 | ||
6385 | static inline int sg_imbalanced(struct sched_group *group) | |
6386 | { | |
6387 | return group->sgc->imbalance; | |
6388 | } | |
6389 | ||
6390 | /* | |
6391 | * group_has_capacity returns true if the group has spare capacity that could | |
6392 | * be used by some tasks. | |
6393 | * We consider that a group has spare capacity if the * number of task is | |
6394 | * smaller than the number of CPUs or if the usage is lower than the available | |
6395 | * capacity for CFS tasks. | |
6396 | * For the latter, we use a threshold to stabilize the state, to take into | |
6397 | * account the variance of the tasks' load and to return true if the available | |
6398 | * capacity in meaningful for the load balancer. | |
6399 | * As an example, an available capacity of 1% can appear but it doesn't make | |
6400 | * any benefit for the load balance. | |
6401 | */ | |
6402 | static inline bool | |
6403 | group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs) | |
6404 | { | |
6405 | if (sgs->sum_nr_running < sgs->group_weight) | |
6406 | return true; | |
6407 | ||
6408 | if ((sgs->group_capacity * 100) > | |
6409 | (sgs->group_usage * env->sd->imbalance_pct)) | |
6410 | return true; | |
6411 | ||
6412 | return false; | |
6413 | } | |
6414 | ||
6415 | /* | |
6416 | * group_is_overloaded returns true if the group has more tasks than it can | |
6417 | * handle. | |
6418 | * group_is_overloaded is not equals to !group_has_capacity because a group | |
6419 | * with the exact right number of tasks, has no more spare capacity but is not | |
6420 | * overloaded so both group_has_capacity and group_is_overloaded return | |
6421 | * false. | |
6422 | */ | |
6423 | static inline bool | |
6424 | group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs) | |
6425 | { | |
6426 | if (sgs->sum_nr_running <= sgs->group_weight) | |
6427 | return false; | |
6428 | ||
6429 | if ((sgs->group_capacity * 100) < | |
6430 | (sgs->group_usage * env->sd->imbalance_pct)) | |
6431 | return true; | |
6432 | ||
6433 | return false; | |
6434 | } | |
6435 | ||
6436 | static enum group_type group_classify(struct lb_env *env, | |
6437 | struct sched_group *group, | |
6438 | struct sg_lb_stats *sgs) | |
6439 | { | |
6440 | if (sgs->group_no_capacity) | |
6441 | return group_overloaded; | |
6442 | ||
6443 | if (sg_imbalanced(group)) | |
6444 | return group_imbalanced; | |
6445 | ||
6446 | return group_other; | |
6447 | } | |
6448 | ||
6449 | /** | |
6450 | * update_sg_lb_stats - Update sched_group's statistics for load balancing. | |
6451 | * @env: The load balancing environment. | |
6452 | * @group: sched_group whose statistics are to be updated. | |
6453 | * @load_idx: Load index of sched_domain of this_cpu for load calc. | |
6454 | * @local_group: Does group contain this_cpu. | |
6455 | * @sgs: variable to hold the statistics for this group. | |
6456 | * @overload: Indicate more than one runnable task for any CPU. | |
6457 | */ | |
6458 | static inline void update_sg_lb_stats(struct lb_env *env, | |
6459 | struct sched_group *group, int load_idx, | |
6460 | int local_group, struct sg_lb_stats *sgs, | |
6461 | bool *overload) | |
6462 | { | |
6463 | unsigned long load; | |
6464 | int i; | |
6465 | ||
6466 | memset(sgs, 0, sizeof(*sgs)); | |
6467 | ||
6468 | for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { | |
6469 | struct rq *rq = cpu_rq(i); | |
6470 | ||
6471 | /* Bias balancing toward cpus of our domain */ | |
6472 | if (local_group) | |
6473 | load = target_load(i, load_idx); | |
6474 | else | |
6475 | load = source_load(i, load_idx); | |
6476 | ||
6477 | sgs->group_load += load; | |
6478 | sgs->group_usage += get_cpu_usage(i); | |
6479 | sgs->sum_nr_running += rq->cfs.h_nr_running; | |
6480 | ||
6481 | if (rq->nr_running > 1) | |
6482 | *overload = true; | |
6483 | ||
6484 | #ifdef CONFIG_NUMA_BALANCING | |
6485 | sgs->nr_numa_running += rq->nr_numa_running; | |
6486 | sgs->nr_preferred_running += rq->nr_preferred_running; | |
6487 | #endif | |
6488 | sgs->sum_weighted_load += weighted_cpuload(i); | |
6489 | if (idle_cpu(i)) | |
6490 | sgs->idle_cpus++; | |
6491 | } | |
6492 | ||
6493 | /* Adjust by relative CPU capacity of the group */ | |
6494 | sgs->group_capacity = group->sgc->capacity; | |
6495 | sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity; | |
6496 | ||
6497 | if (sgs->sum_nr_running) | |
6498 | sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; | |
6499 | ||
6500 | sgs->group_weight = group->group_weight; | |
6501 | ||
6502 | sgs->group_no_capacity = group_is_overloaded(env, sgs); | |
6503 | sgs->group_type = group_classify(env, group, sgs); | |
6504 | } | |
6505 | ||
6506 | /** | |
6507 | * update_sd_pick_busiest - return 1 on busiest group | |
6508 | * @env: The load balancing environment. | |
6509 | * @sds: sched_domain statistics | |
6510 | * @sg: sched_group candidate to be checked for being the busiest | |
6511 | * @sgs: sched_group statistics | |
6512 | * | |
6513 | * Determine if @sg is a busier group than the previously selected | |
6514 | * busiest group. | |
6515 | * | |
6516 | * Return: %true if @sg is a busier group than the previously selected | |
6517 | * busiest group. %false otherwise. | |
6518 | */ | |
6519 | static bool update_sd_pick_busiest(struct lb_env *env, | |
6520 | struct sd_lb_stats *sds, | |
6521 | struct sched_group *sg, | |
6522 | struct sg_lb_stats *sgs) | |
6523 | { | |
6524 | struct sg_lb_stats *busiest = &sds->busiest_stat; | |
6525 | ||
6526 | if (sgs->group_type > busiest->group_type) | |
6527 | return true; | |
6528 | ||
6529 | if (sgs->group_type < busiest->group_type) | |
6530 | return false; | |
6531 | ||
6532 | if (sgs->avg_load <= busiest->avg_load) | |
6533 | return false; | |
6534 | ||
6535 | /* This is the busiest node in its class. */ | |
6536 | if (!(env->sd->flags & SD_ASYM_PACKING)) | |
6537 | return true; | |
6538 | ||
6539 | /* | |
6540 | * ASYM_PACKING needs to move all the work to the lowest | |
6541 | * numbered CPUs in the group, therefore mark all groups | |
6542 | * higher than ourself as busy. | |
6543 | */ | |
6544 | if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) { | |
6545 | if (!sds->busiest) | |
6546 | return true; | |
6547 | ||
6548 | if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) | |
6549 | return true; | |
6550 | } | |
6551 | ||
6552 | return false; | |
6553 | } | |
6554 | ||
6555 | #ifdef CONFIG_NUMA_BALANCING | |
6556 | static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) | |
6557 | { | |
6558 | if (sgs->sum_nr_running > sgs->nr_numa_running) | |
6559 | return regular; | |
6560 | if (sgs->sum_nr_running > sgs->nr_preferred_running) | |
6561 | return remote; | |
6562 | return all; | |
6563 | } | |
6564 | ||
6565 | static inline enum fbq_type fbq_classify_rq(struct rq *rq) | |
6566 | { | |
6567 | if (rq->nr_running > rq->nr_numa_running) | |
6568 | return regular; | |
6569 | if (rq->nr_running > rq->nr_preferred_running) | |
6570 | return remote; | |
6571 | return all; | |
6572 | } | |
6573 | #else | |
6574 | static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) | |
6575 | { | |
6576 | return all; | |
6577 | } | |
6578 | ||
6579 | static inline enum fbq_type fbq_classify_rq(struct rq *rq) | |
6580 | { | |
6581 | return regular; | |
6582 | } | |
6583 | #endif /* CONFIG_NUMA_BALANCING */ | |
6584 | ||
6585 | /** | |
6586 | * update_sd_lb_stats - Update sched_domain's statistics for load balancing. | |
6587 | * @env: The load balancing environment. | |
6588 | * @sds: variable to hold the statistics for this sched_domain. | |
6589 | */ | |
6590 | static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) | |
6591 | { | |
6592 | struct sched_domain *child = env->sd->child; | |
6593 | struct sched_group *sg = env->sd->groups; | |
6594 | struct sg_lb_stats tmp_sgs; | |
6595 | int load_idx, prefer_sibling = 0; | |
6596 | bool overload = false; | |
6597 | ||
6598 | if (child && child->flags & SD_PREFER_SIBLING) | |
6599 | prefer_sibling = 1; | |
6600 | ||
6601 | load_idx = get_sd_load_idx(env->sd, env->idle); | |
6602 | ||
6603 | do { | |
6604 | struct sg_lb_stats *sgs = &tmp_sgs; | |
6605 | int local_group; | |
6606 | ||
6607 | local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg)); | |
6608 | if (local_group) { | |
6609 | sds->local = sg; | |
6610 | sgs = &sds->local_stat; | |
6611 | ||
6612 | if (env->idle != CPU_NEWLY_IDLE || | |
6613 | time_after_eq(jiffies, sg->sgc->next_update)) | |
6614 | update_group_capacity(env->sd, env->dst_cpu); | |
6615 | } | |
6616 | ||
6617 | update_sg_lb_stats(env, sg, load_idx, local_group, sgs, | |
6618 | &overload); | |
6619 | ||
6620 | if (local_group) | |
6621 | goto next_group; | |
6622 | ||
6623 | /* | |
6624 | * In case the child domain prefers tasks go to siblings | |
6625 | * first, lower the sg capacity so that we'll try | |
6626 | * and move all the excess tasks away. We lower the capacity | |
6627 | * of a group only if the local group has the capacity to fit | |
6628 | * these excess tasks. The extra check prevents the case where | |
6629 | * you always pull from the heaviest group when it is already | |
6630 | * under-utilized (possible with a large weight task outweighs | |
6631 | * the tasks on the system). | |
6632 | */ | |
6633 | if (prefer_sibling && sds->local && | |
6634 | group_has_capacity(env, &sds->local_stat) && | |
6635 | (sgs->sum_nr_running > 1)) { | |
6636 | sgs->group_no_capacity = 1; | |
6637 | sgs->group_type = group_overloaded; | |
6638 | } | |
6639 | ||
6640 | if (update_sd_pick_busiest(env, sds, sg, sgs)) { | |
6641 | sds->busiest = sg; | |
6642 | sds->busiest_stat = *sgs; | |
6643 | } | |
6644 | ||
6645 | next_group: | |
6646 | /* Now, start updating sd_lb_stats */ | |
6647 | sds->total_load += sgs->group_load; | |
6648 | sds->total_capacity += sgs->group_capacity; | |
6649 | ||
6650 | sg = sg->next; | |
6651 | } while (sg != env->sd->groups); | |
6652 | ||
6653 | if (env->sd->flags & SD_NUMA) | |
6654 | env->fbq_type = fbq_classify_group(&sds->busiest_stat); | |
6655 | ||
6656 | if (!env->sd->parent) { | |
6657 | /* update overload indicator if we are at root domain */ | |
6658 | if (env->dst_rq->rd->overload != overload) | |
6659 | env->dst_rq->rd->overload = overload; | |
6660 | } | |
6661 | ||
6662 | } | |
6663 | ||
6664 | /** | |
6665 | * check_asym_packing - Check to see if the group is packed into the | |
6666 | * sched doman. | |
6667 | * | |
6668 | * This is primarily intended to used at the sibling level. Some | |
6669 | * cores like POWER7 prefer to use lower numbered SMT threads. In the | |
6670 | * case of POWER7, it can move to lower SMT modes only when higher | |
6671 | * threads are idle. When in lower SMT modes, the threads will | |
6672 | * perform better since they share less core resources. Hence when we | |
6673 | * have idle threads, we want them to be the higher ones. | |
6674 | * | |
6675 | * This packing function is run on idle threads. It checks to see if | |
6676 | * the busiest CPU in this domain (core in the P7 case) has a higher | |
6677 | * CPU number than the packing function is being run on. Here we are | |
6678 | * assuming lower CPU number will be equivalent to lower a SMT thread | |
6679 | * number. | |
6680 | * | |
6681 | * Return: 1 when packing is required and a task should be moved to | |
6682 | * this CPU. The amount of the imbalance is returned in *imbalance. | |
6683 | * | |
6684 | * @env: The load balancing environment. | |
6685 | * @sds: Statistics of the sched_domain which is to be packed | |
6686 | */ | |
6687 | static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) | |
6688 | { | |
6689 | int busiest_cpu; | |
6690 | ||
6691 | if (!(env->sd->flags & SD_ASYM_PACKING)) | |
6692 | return 0; | |
6693 | ||
6694 | if (!sds->busiest) | |
6695 | return 0; | |
6696 | ||
6697 | busiest_cpu = group_first_cpu(sds->busiest); | |
6698 | if (env->dst_cpu > busiest_cpu) | |
6699 | return 0; | |
6700 | ||
6701 | env->imbalance = DIV_ROUND_CLOSEST( | |
6702 | sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity, | |
6703 | SCHED_CAPACITY_SCALE); | |
6704 | ||
6705 | return 1; | |
6706 | } | |
6707 | ||
6708 | /** | |
6709 | * fix_small_imbalance - Calculate the minor imbalance that exists | |
6710 | * amongst the groups of a sched_domain, during | |
6711 | * load balancing. | |
6712 | * @env: The load balancing environment. | |
6713 | * @sds: Statistics of the sched_domain whose imbalance is to be calculated. | |
6714 | */ | |
6715 | static inline | |
6716 | void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds) | |
6717 | { | |
6718 | unsigned long tmp, capa_now = 0, capa_move = 0; | |
6719 | unsigned int imbn = 2; | |
6720 | unsigned long scaled_busy_load_per_task; | |
6721 | struct sg_lb_stats *local, *busiest; | |
6722 | ||
6723 | local = &sds->local_stat; | |
6724 | busiest = &sds->busiest_stat; | |
6725 | ||
6726 | if (!local->sum_nr_running) | |
6727 | local->load_per_task = cpu_avg_load_per_task(env->dst_cpu); | |
6728 | else if (busiest->load_per_task > local->load_per_task) | |
6729 | imbn = 1; | |
6730 | ||
6731 | scaled_busy_load_per_task = | |
6732 | (busiest->load_per_task * SCHED_CAPACITY_SCALE) / | |
6733 | busiest->group_capacity; | |
6734 | ||
6735 | if (busiest->avg_load + scaled_busy_load_per_task >= | |
6736 | local->avg_load + (scaled_busy_load_per_task * imbn)) { | |
6737 | env->imbalance = busiest->load_per_task; | |
6738 | return; | |
6739 | } | |
6740 | ||
6741 | /* | |
6742 | * OK, we don't have enough imbalance to justify moving tasks, | |
6743 | * however we may be able to increase total CPU capacity used by | |
6744 | * moving them. | |
6745 | */ | |
6746 | ||
6747 | capa_now += busiest->group_capacity * | |
6748 | min(busiest->load_per_task, busiest->avg_load); | |
6749 | capa_now += local->group_capacity * | |
6750 | min(local->load_per_task, local->avg_load); | |
6751 | capa_now /= SCHED_CAPACITY_SCALE; | |
6752 | ||
6753 | /* Amount of load we'd subtract */ | |
6754 | if (busiest->avg_load > scaled_busy_load_per_task) { | |
6755 | capa_move += busiest->group_capacity * | |
6756 | min(busiest->load_per_task, | |
6757 | busiest->avg_load - scaled_busy_load_per_task); | |
6758 | } | |
6759 | ||
6760 | /* Amount of load we'd add */ | |
6761 | if (busiest->avg_load * busiest->group_capacity < | |
6762 | busiest->load_per_task * SCHED_CAPACITY_SCALE) { | |
6763 | tmp = (busiest->avg_load * busiest->group_capacity) / | |
6764 | local->group_capacity; | |
6765 | } else { | |
6766 | tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) / | |
6767 | local->group_capacity; | |
6768 | } | |
6769 | capa_move += local->group_capacity * | |
6770 | min(local->load_per_task, local->avg_load + tmp); | |
6771 | capa_move /= SCHED_CAPACITY_SCALE; | |
6772 | ||
6773 | /* Move if we gain throughput */ | |
6774 | if (capa_move > capa_now) | |
6775 | env->imbalance = busiest->load_per_task; | |
6776 | } | |
6777 | ||
6778 | /** | |
6779 | * calculate_imbalance - Calculate the amount of imbalance present within the | |
6780 | * groups of a given sched_domain during load balance. | |
6781 | * @env: load balance environment | |
6782 | * @sds: statistics of the sched_domain whose imbalance is to be calculated. | |
6783 | */ | |
6784 | static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds) | |
6785 | { | |
6786 | unsigned long max_pull, load_above_capacity = ~0UL; | |
6787 | struct sg_lb_stats *local, *busiest; | |
6788 | ||
6789 | local = &sds->local_stat; | |
6790 | busiest = &sds->busiest_stat; | |
6791 | ||
6792 | if (busiest->group_type == group_imbalanced) { | |
6793 | /* | |
6794 | * In the group_imb case we cannot rely on group-wide averages | |
6795 | * to ensure cpu-load equilibrium, look at wider averages. XXX | |
6796 | */ | |
6797 | busiest->load_per_task = | |
6798 | min(busiest->load_per_task, sds->avg_load); | |
6799 | } | |
6800 | ||
6801 | /* | |
6802 | * In the presence of smp nice balancing, certain scenarios can have | |
6803 | * max load less than avg load(as we skip the groups at or below | |
6804 | * its cpu_capacity, while calculating max_load..) | |
6805 | */ | |
6806 | if (busiest->avg_load <= sds->avg_load || | |
6807 | local->avg_load >= sds->avg_load) { | |
6808 | env->imbalance = 0; | |
6809 | return fix_small_imbalance(env, sds); | |
6810 | } | |
6811 | ||
6812 | /* | |
6813 | * If there aren't any idle cpus, avoid creating some. | |
6814 | */ | |
6815 | if (busiest->group_type == group_overloaded && | |
6816 | local->group_type == group_overloaded) { | |
6817 | load_above_capacity = busiest->sum_nr_running * | |
6818 | SCHED_LOAD_SCALE; | |
6819 | if (load_above_capacity > busiest->group_capacity) | |
6820 | load_above_capacity -= busiest->group_capacity; | |
6821 | else | |
6822 | load_above_capacity = ~0UL; | |
6823 | } | |
6824 | ||
6825 | /* | |
6826 | * We're trying to get all the cpus to the average_load, so we don't | |
6827 | * want to push ourselves above the average load, nor do we wish to | |
6828 | * reduce the max loaded cpu below the average load. At the same time, | |
6829 | * we also don't want to reduce the group load below the group capacity | |
6830 | * (so that we can implement power-savings policies etc). Thus we look | |
6831 | * for the minimum possible imbalance. | |
6832 | */ | |
6833 | max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity); | |
6834 | ||
6835 | /* How much load to actually move to equalise the imbalance */ | |
6836 | env->imbalance = min( | |
6837 | max_pull * busiest->group_capacity, | |
6838 | (sds->avg_load - local->avg_load) * local->group_capacity | |
6839 | ) / SCHED_CAPACITY_SCALE; | |
6840 | ||
6841 | /* | |
6842 | * if *imbalance is less than the average load per runnable task | |
6843 | * there is no guarantee that any tasks will be moved so we'll have | |
6844 | * a think about bumping its value to force at least one task to be | |
6845 | * moved | |
6846 | */ | |
6847 | if (env->imbalance < busiest->load_per_task) | |
6848 | return fix_small_imbalance(env, sds); | |
6849 | } | |
6850 | ||
6851 | /******* find_busiest_group() helpers end here *********************/ | |
6852 | ||
6853 | /** | |
6854 | * find_busiest_group - Returns the busiest group within the sched_domain | |
6855 | * if there is an imbalance. If there isn't an imbalance, and | |
6856 | * the user has opted for power-savings, it returns a group whose | |
6857 | * CPUs can be put to idle by rebalancing those tasks elsewhere, if | |
6858 | * such a group exists. | |
6859 | * | |
6860 | * Also calculates the amount of weighted load which should be moved | |
6861 | * to restore balance. | |
6862 | * | |
6863 | * @env: The load balancing environment. | |
6864 | * | |
6865 | * Return: - The busiest group if imbalance exists. | |
6866 | * - If no imbalance and user has opted for power-savings balance, | |
6867 | * return the least loaded group whose CPUs can be | |
6868 | * put to idle by rebalancing its tasks onto our group. | |
6869 | */ | |
6870 | static struct sched_group *find_busiest_group(struct lb_env *env) | |
6871 | { | |
6872 | struct sg_lb_stats *local, *busiest; | |
6873 | struct sd_lb_stats sds; | |
6874 | ||
6875 | init_sd_lb_stats(&sds); | |
6876 | ||
6877 | /* | |
6878 | * Compute the various statistics relavent for load balancing at | |
6879 | * this level. | |
6880 | */ | |
6881 | update_sd_lb_stats(env, &sds); | |
6882 | local = &sds.local_stat; | |
6883 | busiest = &sds.busiest_stat; | |
6884 | ||
6885 | /* ASYM feature bypasses nice load balance check */ | |
6886 | if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) && | |
6887 | check_asym_packing(env, &sds)) | |
6888 | return sds.busiest; | |
6889 | ||
6890 | /* There is no busy sibling group to pull tasks from */ | |
6891 | if (!sds.busiest || busiest->sum_nr_running == 0) | |
6892 | goto out_balanced; | |
6893 | ||
6894 | sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load) | |
6895 | / sds.total_capacity; | |
6896 | ||
6897 | /* | |
6898 | * If the busiest group is imbalanced the below checks don't | |
6899 | * work because they assume all things are equal, which typically | |
6900 | * isn't true due to cpus_allowed constraints and the like. | |
6901 | */ | |
6902 | if (busiest->group_type == group_imbalanced) | |
6903 | goto force_balance; | |
6904 | ||
6905 | /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */ | |
6906 | if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) && | |
6907 | busiest->group_no_capacity) | |
6908 | goto force_balance; | |
6909 | ||
6910 | /* | |
6911 | * If the local group is busier than the selected busiest group | |
6912 | * don't try and pull any tasks. | |
6913 | */ | |
6914 | if (local->avg_load >= busiest->avg_load) | |
6915 | goto out_balanced; | |
6916 | ||
6917 | /* | |
6918 | * Don't pull any tasks if this group is already above the domain | |
6919 | * average load. | |
6920 | */ | |
6921 | if (local->avg_load >= sds.avg_load) | |
6922 | goto out_balanced; | |
6923 | ||
6924 | if (env->idle == CPU_IDLE) { | |
6925 | /* | |
6926 | * This cpu is idle. If the busiest group is not overloaded | |
6927 | * and there is no imbalance between this and busiest group | |
6928 | * wrt idle cpus, it is balanced. The imbalance becomes | |
6929 | * significant if the diff is greater than 1 otherwise we | |
6930 | * might end up to just move the imbalance on another group | |
6931 | */ | |
6932 | if ((busiest->group_type != group_overloaded) && | |
6933 | (local->idle_cpus <= (busiest->idle_cpus + 1))) | |
6934 | goto out_balanced; | |
6935 | } else { | |
6936 | /* | |
6937 | * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use | |
6938 | * imbalance_pct to be conservative. | |
6939 | */ | |
6940 | if (100 * busiest->avg_load <= | |
6941 | env->sd->imbalance_pct * local->avg_load) | |
6942 | goto out_balanced; | |
6943 | } | |
6944 | ||
6945 | force_balance: | |
6946 | /* Looks like there is an imbalance. Compute it */ | |
6947 | calculate_imbalance(env, &sds); | |
6948 | return sds.busiest; | |
6949 | ||
6950 | out_balanced: | |
6951 | env->imbalance = 0; | |
6952 | return NULL; | |
6953 | } | |
6954 | ||
6955 | /* | |
6956 | * find_busiest_queue - find the busiest runqueue among the cpus in group. | |
6957 | */ | |
6958 | static struct rq *find_busiest_queue(struct lb_env *env, | |
6959 | struct sched_group *group) | |
6960 | { | |
6961 | struct rq *busiest = NULL, *rq; | |
6962 | unsigned long busiest_load = 0, busiest_capacity = 1; | |
6963 | int i; | |
6964 | ||
6965 | for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { | |
6966 | unsigned long capacity, wl; | |
6967 | enum fbq_type rt; | |
6968 | ||
6969 | rq = cpu_rq(i); | |
6970 | rt = fbq_classify_rq(rq); | |
6971 | ||
6972 | /* | |
6973 | * We classify groups/runqueues into three groups: | |
6974 | * - regular: there are !numa tasks | |
6975 | * - remote: there are numa tasks that run on the 'wrong' node | |
6976 | * - all: there is no distinction | |
6977 | * | |
6978 | * In order to avoid migrating ideally placed numa tasks, | |
6979 | * ignore those when there's better options. | |
6980 | * | |
6981 | * If we ignore the actual busiest queue to migrate another | |
6982 | * task, the next balance pass can still reduce the busiest | |
6983 | * queue by moving tasks around inside the node. | |
6984 | * | |
6985 | * If we cannot move enough load due to this classification | |
6986 | * the next pass will adjust the group classification and | |
6987 | * allow migration of more tasks. | |
6988 | * | |
6989 | * Both cases only affect the total convergence complexity. | |
6990 | */ | |
6991 | if (rt > env->fbq_type) | |
6992 | continue; | |
6993 | ||
6994 | capacity = capacity_of(i); | |
6995 | ||
6996 | wl = weighted_cpuload(i); | |
6997 | ||
6998 | /* | |
6999 | * When comparing with imbalance, use weighted_cpuload() | |
7000 | * which is not scaled with the cpu capacity. | |
7001 | */ | |
7002 | ||
7003 | if (rq->nr_running == 1 && wl > env->imbalance && | |
7004 | !check_cpu_capacity(rq, env->sd)) | |
7005 | continue; | |
7006 | ||
7007 | /* | |
7008 | * For the load comparisons with the other cpu's, consider | |
7009 | * the weighted_cpuload() scaled with the cpu capacity, so | |
7010 | * that the load can be moved away from the cpu that is | |
7011 | * potentially running at a lower capacity. | |
7012 | * | |
7013 | * Thus we're looking for max(wl_i / capacity_i), crosswise | |
7014 | * multiplication to rid ourselves of the division works out | |
7015 | * to: wl_i * capacity_j > wl_j * capacity_i; where j is | |
7016 | * our previous maximum. | |
7017 | */ | |
7018 | if (wl * busiest_capacity > busiest_load * capacity) { | |
7019 | busiest_load = wl; | |
7020 | busiest_capacity = capacity; | |
7021 | busiest = rq; | |
7022 | } | |
7023 | } | |
7024 | ||
7025 | return busiest; | |
7026 | } | |
7027 | ||
7028 | /* | |
7029 | * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but | |
7030 | * so long as it is large enough. | |
7031 | */ | |
7032 | #define MAX_PINNED_INTERVAL 512 | |
7033 | ||
7034 | /* Working cpumask for load_balance and load_balance_newidle. */ | |
7035 | DEFINE_PER_CPU(cpumask_var_t, load_balance_mask); | |
7036 | ||
7037 | static int need_active_balance(struct lb_env *env) | |
7038 | { | |
7039 | struct sched_domain *sd = env->sd; | |
7040 | ||
7041 | if (env->idle == CPU_NEWLY_IDLE) { | |
7042 | ||
7043 | /* | |
7044 | * ASYM_PACKING needs to force migrate tasks from busy but | |
7045 | * higher numbered CPUs in order to pack all tasks in the | |
7046 | * lowest numbered CPUs. | |
7047 | */ | |
7048 | if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu) | |
7049 | return 1; | |
7050 | } | |
7051 | ||
7052 | /* | |
7053 | * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task. | |
7054 | * It's worth migrating the task if the src_cpu's capacity is reduced | |
7055 | * because of other sched_class or IRQs if more capacity stays | |
7056 | * available on dst_cpu. | |
7057 | */ | |
7058 | if ((env->idle != CPU_NOT_IDLE) && | |
7059 | (env->src_rq->cfs.h_nr_running == 1)) { | |
7060 | if ((check_cpu_capacity(env->src_rq, sd)) && | |
7061 | (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100)) | |
7062 | return 1; | |
7063 | } | |
7064 | ||
7065 | return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); | |
7066 | } | |
7067 | ||
7068 | static int active_load_balance_cpu_stop(void *data); | |
7069 | ||
7070 | static int should_we_balance(struct lb_env *env) | |
7071 | { | |
7072 | struct sched_group *sg = env->sd->groups; | |
7073 | struct cpumask *sg_cpus, *sg_mask; | |
7074 | int cpu, balance_cpu = -1; | |
7075 | ||
7076 | /* | |
7077 | * In the newly idle case, we will allow all the cpu's | |
7078 | * to do the newly idle load balance. | |
7079 | */ | |
7080 | if (env->idle == CPU_NEWLY_IDLE) | |
7081 | return 1; | |
7082 | ||
7083 | sg_cpus = sched_group_cpus(sg); | |
7084 | sg_mask = sched_group_mask(sg); | |
7085 | /* Try to find first idle cpu */ | |
7086 | for_each_cpu_and(cpu, sg_cpus, env->cpus) { | |
7087 | if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu)) | |
7088 | continue; | |
7089 | ||
7090 | balance_cpu = cpu; | |
7091 | break; | |
7092 | } | |
7093 | ||
7094 | if (balance_cpu == -1) | |
7095 | balance_cpu = group_balance_cpu(sg); | |
7096 | ||
7097 | /* | |
7098 | * First idle cpu or the first cpu(busiest) in this sched group | |
7099 | * is eligible for doing load balancing at this and above domains. | |
7100 | */ | |
7101 | return balance_cpu == env->dst_cpu; | |
7102 | } | |
7103 | ||
7104 | /* | |
7105 | * Check this_cpu to ensure it is balanced within domain. Attempt to move | |
7106 | * tasks if there is an imbalance. | |
7107 | */ | |
7108 | static int load_balance(int this_cpu, struct rq *this_rq, | |
7109 | struct sched_domain *sd, enum cpu_idle_type idle, | |
7110 | int *continue_balancing) | |
7111 | { | |
7112 | int ld_moved, cur_ld_moved, active_balance = 0; | |
7113 | struct sched_domain *sd_parent = sd->parent; | |
7114 | struct sched_group *group; | |
7115 | struct rq *busiest; | |
7116 | unsigned long flags; | |
7117 | struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask); | |
7118 | ||
7119 | struct lb_env env = { | |
7120 | .sd = sd, | |
7121 | .dst_cpu = this_cpu, | |
7122 | .dst_rq = this_rq, | |
7123 | .dst_grpmask = sched_group_cpus(sd->groups), | |
7124 | .idle = idle, | |
7125 | .loop_break = sched_nr_migrate_break, | |
7126 | .cpus = cpus, | |
7127 | .fbq_type = all, | |
7128 | .tasks = LIST_HEAD_INIT(env.tasks), | |
7129 | }; | |
7130 | ||
7131 | /* | |
7132 | * For NEWLY_IDLE load_balancing, we don't need to consider | |
7133 | * other cpus in our group | |
7134 | */ | |
7135 | if (idle == CPU_NEWLY_IDLE) | |
7136 | env.dst_grpmask = NULL; | |
7137 | ||
7138 | cpumask_copy(cpus, cpu_active_mask); | |
7139 | ||
7140 | schedstat_inc(sd, lb_count[idle]); | |
7141 | ||
7142 | redo: | |
7143 | if (!should_we_balance(&env)) { | |
7144 | *continue_balancing = 0; | |
7145 | goto out_balanced; | |
7146 | } | |
7147 | ||
7148 | group = find_busiest_group(&env); | |
7149 | if (!group) { | |
7150 | schedstat_inc(sd, lb_nobusyg[idle]); | |
7151 | goto out_balanced; | |
7152 | } | |
7153 | ||
7154 | busiest = find_busiest_queue(&env, group); | |
7155 | if (!busiest) { | |
7156 | schedstat_inc(sd, lb_nobusyq[idle]); | |
7157 | goto out_balanced; | |
7158 | } | |
7159 | ||
7160 | BUG_ON(busiest == env.dst_rq); | |
7161 | ||
7162 | schedstat_add(sd, lb_imbalance[idle], env.imbalance); | |
7163 | ||
7164 | env.src_cpu = busiest->cpu; | |
7165 | env.src_rq = busiest; | |
7166 | ||
7167 | ld_moved = 0; | |
7168 | if (busiest->nr_running > 1) { | |
7169 | /* | |
7170 | * Attempt to move tasks. If find_busiest_group has found | |
7171 | * an imbalance but busiest->nr_running <= 1, the group is | |
7172 | * still unbalanced. ld_moved simply stays zero, so it is | |
7173 | * correctly treated as an imbalance. | |
7174 | */ | |
7175 | env.flags |= LBF_ALL_PINNED; | |
7176 | env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); | |
7177 | ||
7178 | more_balance: | |
7179 | raw_spin_lock_irqsave(&busiest->lock, flags); | |
7180 | ||
7181 | /* | |
7182 | * cur_ld_moved - load moved in current iteration | |
7183 | * ld_moved - cumulative load moved across iterations | |
7184 | */ | |
7185 | cur_ld_moved = detach_tasks(&env); | |
7186 | ||
7187 | /* | |
7188 | * We've detached some tasks from busiest_rq. Every | |
7189 | * task is masked "TASK_ON_RQ_MIGRATING", so we can safely | |
7190 | * unlock busiest->lock, and we are able to be sure | |
7191 | * that nobody can manipulate the tasks in parallel. | |
7192 | * See task_rq_lock() family for the details. | |
7193 | */ | |
7194 | ||
7195 | raw_spin_unlock(&busiest->lock); | |
7196 | ||
7197 | if (cur_ld_moved) { | |
7198 | attach_tasks(&env); | |
7199 | ld_moved += cur_ld_moved; | |
7200 | } | |
7201 | ||
7202 | local_irq_restore(flags); | |
7203 | ||
7204 | if (env.flags & LBF_NEED_BREAK) { | |
7205 | env.flags &= ~LBF_NEED_BREAK; | |
7206 | goto more_balance; | |
7207 | } | |
7208 | ||
7209 | /* | |
7210 | * Revisit (affine) tasks on src_cpu that couldn't be moved to | |
7211 | * us and move them to an alternate dst_cpu in our sched_group | |
7212 | * where they can run. The upper limit on how many times we | |
7213 | * iterate on same src_cpu is dependent on number of cpus in our | |
7214 | * sched_group. | |
7215 | * | |
7216 | * This changes load balance semantics a bit on who can move | |
7217 | * load to a given_cpu. In addition to the given_cpu itself | |
7218 | * (or a ilb_cpu acting on its behalf where given_cpu is | |
7219 | * nohz-idle), we now have balance_cpu in a position to move | |
7220 | * load to given_cpu. In rare situations, this may cause | |
7221 | * conflicts (balance_cpu and given_cpu/ilb_cpu deciding | |
7222 | * _independently_ and at _same_ time to move some load to | |
7223 | * given_cpu) causing exceess load to be moved to given_cpu. | |
7224 | * This however should not happen so much in practice and | |
7225 | * moreover subsequent load balance cycles should correct the | |
7226 | * excess load moved. | |
7227 | */ | |
7228 | if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) { | |
7229 | ||
7230 | /* Prevent to re-select dst_cpu via env's cpus */ | |
7231 | cpumask_clear_cpu(env.dst_cpu, env.cpus); | |
7232 | ||
7233 | env.dst_rq = cpu_rq(env.new_dst_cpu); | |
7234 | env.dst_cpu = env.new_dst_cpu; | |
7235 | env.flags &= ~LBF_DST_PINNED; | |
7236 | env.loop = 0; | |
7237 | env.loop_break = sched_nr_migrate_break; | |
7238 | ||
7239 | /* | |
7240 | * Go back to "more_balance" rather than "redo" since we | |
7241 | * need to continue with same src_cpu. | |
7242 | */ | |
7243 | goto more_balance; | |
7244 | } | |
7245 | ||
7246 | /* | |
7247 | * We failed to reach balance because of affinity. | |
7248 | */ | |
7249 | if (sd_parent) { | |
7250 | int *group_imbalance = &sd_parent->groups->sgc->imbalance; | |
7251 | ||
7252 | if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) | |
7253 | *group_imbalance = 1; | |
7254 | } | |
7255 | ||
7256 | /* All tasks on this runqueue were pinned by CPU affinity */ | |
7257 | if (unlikely(env.flags & LBF_ALL_PINNED)) { | |
7258 | cpumask_clear_cpu(cpu_of(busiest), cpus); | |
7259 | if (!cpumask_empty(cpus)) { | |
7260 | env.loop = 0; | |
7261 | env.loop_break = sched_nr_migrate_break; | |
7262 | goto redo; | |
7263 | } | |
7264 | goto out_all_pinned; | |
7265 | } | |
7266 | } | |
7267 | ||
7268 | if (!ld_moved) { | |
7269 | schedstat_inc(sd, lb_failed[idle]); | |
7270 | /* | |
7271 | * Increment the failure counter only on periodic balance. | |
7272 | * We do not want newidle balance, which can be very | |
7273 | * frequent, pollute the failure counter causing | |
7274 | * excessive cache_hot migrations and active balances. | |
7275 | */ | |
7276 | if (idle != CPU_NEWLY_IDLE) | |
7277 | sd->nr_balance_failed++; | |
7278 | ||
7279 | if (need_active_balance(&env)) { | |
7280 | raw_spin_lock_irqsave(&busiest->lock, flags); | |
7281 | ||
7282 | /* don't kick the active_load_balance_cpu_stop, | |
7283 | * if the curr task on busiest cpu can't be | |
7284 | * moved to this_cpu | |
7285 | */ | |
7286 | if (!cpumask_test_cpu(this_cpu, | |
7287 | tsk_cpus_allowed(busiest->curr))) { | |
7288 | raw_spin_unlock_irqrestore(&busiest->lock, | |
7289 | flags); | |
7290 | env.flags |= LBF_ALL_PINNED; | |
7291 | goto out_one_pinned; | |
7292 | } | |
7293 | ||
7294 | /* | |
7295 | * ->active_balance synchronizes accesses to | |
7296 | * ->active_balance_work. Once set, it's cleared | |
7297 | * only after active load balance is finished. | |
7298 | */ | |
7299 | if (!busiest->active_balance) { | |
7300 | busiest->active_balance = 1; | |
7301 | busiest->push_cpu = this_cpu; | |
7302 | active_balance = 1; | |
7303 | } | |
7304 | raw_spin_unlock_irqrestore(&busiest->lock, flags); | |
7305 | ||
7306 | if (active_balance) { | |
7307 | stop_one_cpu_nowait(cpu_of(busiest), | |
7308 | active_load_balance_cpu_stop, busiest, | |
7309 | &busiest->active_balance_work); | |
7310 | } | |
7311 | ||
7312 | /* | |
7313 | * We've kicked active balancing, reset the failure | |
7314 | * counter. | |
7315 | */ | |
7316 | sd->nr_balance_failed = sd->cache_nice_tries+1; | |
7317 | } | |
7318 | } else | |
7319 | sd->nr_balance_failed = 0; | |
7320 | ||
7321 | if (likely(!active_balance)) { | |
7322 | /* We were unbalanced, so reset the balancing interval */ | |
7323 | sd->balance_interval = sd->min_interval; | |
7324 | } else { | |
7325 | /* | |
7326 | * If we've begun active balancing, start to back off. This | |
7327 | * case may not be covered by the all_pinned logic if there | |
7328 | * is only 1 task on the busy runqueue (because we don't call | |
7329 | * detach_tasks). | |
7330 | */ | |
7331 | if (sd->balance_interval < sd->max_interval) | |
7332 | sd->balance_interval *= 2; | |
7333 | } | |
7334 | ||
7335 | goto out; | |
7336 | ||
7337 | out_balanced: | |
7338 | /* | |
7339 | * We reach balance although we may have faced some affinity | |
7340 | * constraints. Clear the imbalance flag if it was set. | |
7341 | */ | |
7342 | if (sd_parent) { | |
7343 | int *group_imbalance = &sd_parent->groups->sgc->imbalance; | |
7344 | ||
7345 | if (*group_imbalance) | |
7346 | *group_imbalance = 0; | |
7347 | } | |
7348 | ||
7349 | out_all_pinned: | |
7350 | /* | |
7351 | * We reach balance because all tasks are pinned at this level so | |
7352 | * we can't migrate them. Let the imbalance flag set so parent level | |
7353 | * can try to migrate them. | |
7354 | */ | |
7355 | schedstat_inc(sd, lb_balanced[idle]); | |
7356 | ||
7357 | sd->nr_balance_failed = 0; | |
7358 | ||
7359 | out_one_pinned: | |
7360 | /* tune up the balancing interval */ | |
7361 | if (((env.flags & LBF_ALL_PINNED) && | |
7362 | sd->balance_interval < MAX_PINNED_INTERVAL) || | |
7363 | (sd->balance_interval < sd->max_interval)) | |
7364 | sd->balance_interval *= 2; | |
7365 | ||
7366 | ld_moved = 0; | |
7367 | out: | |
7368 | return ld_moved; | |
7369 | } | |
7370 | ||
7371 | static inline unsigned long | |
7372 | get_sd_balance_interval(struct sched_domain *sd, int cpu_busy) | |
7373 | { | |
7374 | unsigned long interval = sd->balance_interval; | |
7375 | ||
7376 | if (cpu_busy) | |
7377 | interval *= sd->busy_factor; | |
7378 | ||
7379 | /* scale ms to jiffies */ | |
7380 | interval = msecs_to_jiffies(interval); | |
7381 | interval = clamp(interval, 1UL, max_load_balance_interval); | |
7382 | ||
7383 | return interval; | |
7384 | } | |
7385 | ||
7386 | static inline void | |
7387 | update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance) | |
7388 | { | |
7389 | unsigned long interval, next; | |
7390 | ||
7391 | interval = get_sd_balance_interval(sd, cpu_busy); | |
7392 | next = sd->last_balance + interval; | |
7393 | ||
7394 | if (time_after(*next_balance, next)) | |
7395 | *next_balance = next; | |
7396 | } | |
7397 | ||
7398 | /* | |
7399 | * idle_balance is called by schedule() if this_cpu is about to become | |
7400 | * idle. Attempts to pull tasks from other CPUs. | |
7401 | */ | |
7402 | static int idle_balance(struct rq *this_rq) | |
7403 | { | |
7404 | unsigned long next_balance = jiffies + HZ; | |
7405 | int this_cpu = this_rq->cpu; | |
7406 | struct sched_domain *sd; | |
7407 | int pulled_task = 0; | |
7408 | u64 curr_cost = 0; | |
7409 | ||
7410 | idle_enter_fair(this_rq); | |
7411 | ||
7412 | /* | |
7413 | * We must set idle_stamp _before_ calling idle_balance(), such that we | |
7414 | * measure the duration of idle_balance() as idle time. | |
7415 | */ | |
7416 | this_rq->idle_stamp = rq_clock(this_rq); | |
7417 | ||
7418 | if (this_rq->avg_idle < sysctl_sched_migration_cost || | |
7419 | !this_rq->rd->overload) { | |
7420 | rcu_read_lock(); | |
7421 | sd = rcu_dereference_check_sched_domain(this_rq->sd); | |
7422 | if (sd) | |
7423 | update_next_balance(sd, 0, &next_balance); | |
7424 | rcu_read_unlock(); | |
7425 | ||
7426 | goto out; | |
7427 | } | |
7428 | ||
7429 | /* | |
7430 | * Drop the rq->lock, but keep IRQ/preempt disabled. | |
7431 | */ | |
7432 | raw_spin_unlock(&this_rq->lock); | |
7433 | ||
7434 | update_blocked_averages(this_cpu); | |
7435 | rcu_read_lock(); | |
7436 | for_each_domain(this_cpu, sd) { | |
7437 | int continue_balancing = 1; | |
7438 | u64 t0, domain_cost; | |
7439 | ||
7440 | if (!(sd->flags & SD_LOAD_BALANCE)) | |
7441 | continue; | |
7442 | ||
7443 | if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) { | |
7444 | update_next_balance(sd, 0, &next_balance); | |
7445 | break; | |
7446 | } | |
7447 | ||
7448 | if (sd->flags & SD_BALANCE_NEWIDLE) { | |
7449 | t0 = sched_clock_cpu(this_cpu); | |
7450 | ||
7451 | pulled_task = load_balance(this_cpu, this_rq, | |
7452 | sd, CPU_NEWLY_IDLE, | |
7453 | &continue_balancing); | |
7454 | ||
7455 | domain_cost = sched_clock_cpu(this_cpu) - t0; | |
7456 | if (domain_cost > sd->max_newidle_lb_cost) | |
7457 | sd->max_newidle_lb_cost = domain_cost; | |
7458 | ||
7459 | curr_cost += domain_cost; | |
7460 | } | |
7461 | ||
7462 | update_next_balance(sd, 0, &next_balance); | |
7463 | ||
7464 | /* | |
7465 | * Stop searching for tasks to pull if there are | |
7466 | * now runnable tasks on this rq. | |
7467 | */ | |
7468 | if (pulled_task || this_rq->nr_running > 0) | |
7469 | break; | |
7470 | } | |
7471 | rcu_read_unlock(); | |
7472 | ||
7473 | raw_spin_lock(&this_rq->lock); | |
7474 | ||
7475 | if (curr_cost > this_rq->max_idle_balance_cost) | |
7476 | this_rq->max_idle_balance_cost = curr_cost; | |
7477 | ||
7478 | /* | |
7479 | * While browsing the domains, we released the rq lock, a task could | |
7480 | * have been enqueued in the meantime. Since we're not going idle, | |
7481 | * pretend we pulled a task. | |
7482 | */ | |
7483 | if (this_rq->cfs.h_nr_running && !pulled_task) | |
7484 | pulled_task = 1; | |
7485 | ||
7486 | out: | |
7487 | /* Move the next balance forward */ | |
7488 | if (time_after(this_rq->next_balance, next_balance)) | |
7489 | this_rq->next_balance = next_balance; | |
7490 | ||
7491 | /* Is there a task of a high priority class? */ | |
7492 | if (this_rq->nr_running != this_rq->cfs.h_nr_running) | |
7493 | pulled_task = -1; | |
7494 | ||
7495 | if (pulled_task) { | |
7496 | idle_exit_fair(this_rq); | |
7497 | this_rq->idle_stamp = 0; | |
7498 | } | |
7499 | ||
7500 | return pulled_task; | |
7501 | } | |
7502 | ||
7503 | /* | |
7504 | * active_load_balance_cpu_stop is run by cpu stopper. It pushes | |
7505 | * running tasks off the busiest CPU onto idle CPUs. It requires at | |
7506 | * least 1 task to be running on each physical CPU where possible, and | |
7507 | * avoids physical / logical imbalances. | |
7508 | */ | |
7509 | static int active_load_balance_cpu_stop(void *data) | |
7510 | { | |
7511 | struct rq *busiest_rq = data; | |
7512 | int busiest_cpu = cpu_of(busiest_rq); | |
7513 | int target_cpu = busiest_rq->push_cpu; | |
7514 | struct rq *target_rq = cpu_rq(target_cpu); | |
7515 | struct sched_domain *sd; | |
7516 | struct task_struct *p = NULL; | |
7517 | ||
7518 | raw_spin_lock_irq(&busiest_rq->lock); | |
7519 | ||
7520 | /* make sure the requested cpu hasn't gone down in the meantime */ | |
7521 | if (unlikely(busiest_cpu != smp_processor_id() || | |
7522 | !busiest_rq->active_balance)) | |
7523 | goto out_unlock; | |
7524 | ||
7525 | /* Is there any task to move? */ | |
7526 | if (busiest_rq->nr_running <= 1) | |
7527 | goto out_unlock; | |
7528 | ||
7529 | /* | |
7530 | * This condition is "impossible", if it occurs | |
7531 | * we need to fix it. Originally reported by | |
7532 | * Bjorn Helgaas on a 128-cpu setup. | |
7533 | */ | |
7534 | BUG_ON(busiest_rq == target_rq); | |
7535 | ||
7536 | /* Search for an sd spanning us and the target CPU. */ | |
7537 | rcu_read_lock(); | |
7538 | for_each_domain(target_cpu, sd) { | |
7539 | if ((sd->flags & SD_LOAD_BALANCE) && | |
7540 | cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) | |
7541 | break; | |
7542 | } | |
7543 | ||
7544 | if (likely(sd)) { | |
7545 | struct lb_env env = { | |
7546 | .sd = sd, | |
7547 | .dst_cpu = target_cpu, | |
7548 | .dst_rq = target_rq, | |
7549 | .src_cpu = busiest_rq->cpu, | |
7550 | .src_rq = busiest_rq, | |
7551 | .idle = CPU_IDLE, | |
7552 | }; | |
7553 | ||
7554 | schedstat_inc(sd, alb_count); | |
7555 | ||
7556 | p = detach_one_task(&env); | |
7557 | if (p) | |
7558 | schedstat_inc(sd, alb_pushed); | |
7559 | else | |
7560 | schedstat_inc(sd, alb_failed); | |
7561 | } | |
7562 | rcu_read_unlock(); | |
7563 | out_unlock: | |
7564 | busiest_rq->active_balance = 0; | |
7565 | raw_spin_unlock(&busiest_rq->lock); | |
7566 | ||
7567 | if (p) | |
7568 | attach_one_task(target_rq, p); | |
7569 | ||
7570 | local_irq_enable(); | |
7571 | ||
7572 | return 0; | |
7573 | } | |
7574 | ||
7575 | static inline int on_null_domain(struct rq *rq) | |
7576 | { | |
7577 | return unlikely(!rcu_dereference_sched(rq->sd)); | |
7578 | } | |
7579 | ||
7580 | #ifdef CONFIG_NO_HZ_COMMON | |
7581 | /* | |
7582 | * idle load balancing details | |
7583 | * - When one of the busy CPUs notice that there may be an idle rebalancing | |
7584 | * needed, they will kick the idle load balancer, which then does idle | |
7585 | * load balancing for all the idle CPUs. | |
7586 | */ | |
7587 | static struct { | |
7588 | cpumask_var_t idle_cpus_mask; | |
7589 | atomic_t nr_cpus; | |
7590 | unsigned long next_balance; /* in jiffy units */ | |
7591 | } nohz ____cacheline_aligned; | |
7592 | ||
7593 | static inline int find_new_ilb(void) | |
7594 | { | |
7595 | int ilb = cpumask_first(nohz.idle_cpus_mask); | |
7596 | ||
7597 | if (ilb < nr_cpu_ids && idle_cpu(ilb)) | |
7598 | return ilb; | |
7599 | ||
7600 | return nr_cpu_ids; | |
7601 | } | |
7602 | ||
7603 | /* | |
7604 | * Kick a CPU to do the nohz balancing, if it is time for it. We pick the | |
7605 | * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle | |
7606 | * CPU (if there is one). | |
7607 | */ | |
7608 | static void nohz_balancer_kick(void) | |
7609 | { | |
7610 | int ilb_cpu; | |
7611 | ||
7612 | nohz.next_balance++; | |
7613 | ||
7614 | ilb_cpu = find_new_ilb(); | |
7615 | ||
7616 | if (ilb_cpu >= nr_cpu_ids) | |
7617 | return; | |
7618 | ||
7619 | if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu))) | |
7620 | return; | |
7621 | /* | |
7622 | * Use smp_send_reschedule() instead of resched_cpu(). | |
7623 | * This way we generate a sched IPI on the target cpu which | |
7624 | * is idle. And the softirq performing nohz idle load balance | |
7625 | * will be run before returning from the IPI. | |
7626 | */ | |
7627 | smp_send_reschedule(ilb_cpu); | |
7628 | return; | |
7629 | } | |
7630 | ||
7631 | static inline void nohz_balance_exit_idle(int cpu) | |
7632 | { | |
7633 | if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) { | |
7634 | /* | |
7635 | * Completely isolated CPUs don't ever set, so we must test. | |
7636 | */ | |
7637 | if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) { | |
7638 | cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); | |
7639 | atomic_dec(&nohz.nr_cpus); | |
7640 | } | |
7641 | clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); | |
7642 | } | |
7643 | } | |
7644 | ||
7645 | static inline void set_cpu_sd_state_busy(void) | |
7646 | { | |
7647 | struct sched_domain *sd; | |
7648 | int cpu = smp_processor_id(); | |
7649 | ||
7650 | rcu_read_lock(); | |
7651 | sd = rcu_dereference(per_cpu(sd_busy, cpu)); | |
7652 | ||
7653 | if (!sd || !sd->nohz_idle) | |
7654 | goto unlock; | |
7655 | sd->nohz_idle = 0; | |
7656 | ||
7657 | atomic_inc(&sd->groups->sgc->nr_busy_cpus); | |
7658 | unlock: | |
7659 | rcu_read_unlock(); | |
7660 | } | |
7661 | ||
7662 | void set_cpu_sd_state_idle(void) | |
7663 | { | |
7664 | struct sched_domain *sd; | |
7665 | int cpu = smp_processor_id(); | |
7666 | ||
7667 | rcu_read_lock(); | |
7668 | sd = rcu_dereference(per_cpu(sd_busy, cpu)); | |
7669 | ||
7670 | if (!sd || sd->nohz_idle) | |
7671 | goto unlock; | |
7672 | sd->nohz_idle = 1; | |
7673 | ||
7674 | atomic_dec(&sd->groups->sgc->nr_busy_cpus); | |
7675 | unlock: | |
7676 | rcu_read_unlock(); | |
7677 | } | |
7678 | ||
7679 | /* | |
7680 | * This routine will record that the cpu is going idle with tick stopped. | |
7681 | * This info will be used in performing idle load balancing in the future. | |
7682 | */ | |
7683 | void nohz_balance_enter_idle(int cpu) | |
7684 | { | |
7685 | /* | |
7686 | * If this cpu is going down, then nothing needs to be done. | |
7687 | */ | |
7688 | if (!cpu_active(cpu)) | |
7689 | return; | |
7690 | ||
7691 | if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu))) | |
7692 | return; | |
7693 | ||
7694 | /* | |
7695 | * If we're a completely isolated CPU, we don't play. | |
7696 | */ | |
7697 | if (on_null_domain(cpu_rq(cpu))) | |
7698 | return; | |
7699 | ||
7700 | cpumask_set_cpu(cpu, nohz.idle_cpus_mask); | |
7701 | atomic_inc(&nohz.nr_cpus); | |
7702 | set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); | |
7703 | } | |
7704 | ||
7705 | static int sched_ilb_notifier(struct notifier_block *nfb, | |
7706 | unsigned long action, void *hcpu) | |
7707 | { | |
7708 | switch (action & ~CPU_TASKS_FROZEN) { | |
7709 | case CPU_DYING: | |
7710 | nohz_balance_exit_idle(smp_processor_id()); | |
7711 | return NOTIFY_OK; | |
7712 | default: | |
7713 | return NOTIFY_DONE; | |
7714 | } | |
7715 | } | |
7716 | #endif | |
7717 | ||
7718 | static DEFINE_SPINLOCK(balancing); | |
7719 | ||
7720 | /* | |
7721 | * Scale the max load_balance interval with the number of CPUs in the system. | |
7722 | * This trades load-balance latency on larger machines for less cross talk. | |
7723 | */ | |
7724 | void update_max_interval(void) | |
7725 | { | |
7726 | max_load_balance_interval = HZ*num_online_cpus()/10; | |
7727 | } | |
7728 | ||
7729 | /* | |
7730 | * It checks each scheduling domain to see if it is due to be balanced, | |
7731 | * and initiates a balancing operation if so. | |
7732 | * | |
7733 | * Balancing parameters are set up in init_sched_domains. | |
7734 | */ | |
7735 | static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) | |
7736 | { | |
7737 | int continue_balancing = 1; | |
7738 | int cpu = rq->cpu; | |
7739 | unsigned long interval; | |
7740 | struct sched_domain *sd; | |
7741 | /* Earliest time when we have to do rebalance again */ | |
7742 | unsigned long next_balance = jiffies + 60*HZ; | |
7743 | int update_next_balance = 0; | |
7744 | int need_serialize, need_decay = 0; | |
7745 | u64 max_cost = 0; | |
7746 | ||
7747 | update_blocked_averages(cpu); | |
7748 | ||
7749 | rcu_read_lock(); | |
7750 | for_each_domain(cpu, sd) { | |
7751 | /* | |
7752 | * Decay the newidle max times here because this is a regular | |
7753 | * visit to all the domains. Decay ~1% per second. | |
7754 | */ | |
7755 | if (time_after(jiffies, sd->next_decay_max_lb_cost)) { | |
7756 | sd->max_newidle_lb_cost = | |
7757 | (sd->max_newidle_lb_cost * 253) / 256; | |
7758 | sd->next_decay_max_lb_cost = jiffies + HZ; | |
7759 | need_decay = 1; | |
7760 | } | |
7761 | max_cost += sd->max_newidle_lb_cost; | |
7762 | ||
7763 | if (!(sd->flags & SD_LOAD_BALANCE)) | |
7764 | continue; | |
7765 | ||
7766 | /* | |
7767 | * Stop the load balance at this level. There is another | |
7768 | * CPU in our sched group which is doing load balancing more | |
7769 | * actively. | |
7770 | */ | |
7771 | if (!continue_balancing) { | |
7772 | if (need_decay) | |
7773 | continue; | |
7774 | break; | |
7775 | } | |
7776 | ||
7777 | interval = get_sd_balance_interval(sd, idle != CPU_IDLE); | |
7778 | ||
7779 | need_serialize = sd->flags & SD_SERIALIZE; | |
7780 | if (need_serialize) { | |
7781 | if (!spin_trylock(&balancing)) | |
7782 | goto out; | |
7783 | } | |
7784 | ||
7785 | if (time_after_eq(jiffies, sd->last_balance + interval)) { | |
7786 | if (load_balance(cpu, rq, sd, idle, &continue_balancing)) { | |
7787 | /* | |
7788 | * The LBF_DST_PINNED logic could have changed | |
7789 | * env->dst_cpu, so we can't know our idle | |
7790 | * state even if we migrated tasks. Update it. | |
7791 | */ | |
7792 | idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; | |
7793 | } | |
7794 | sd->last_balance = jiffies; | |
7795 | interval = get_sd_balance_interval(sd, idle != CPU_IDLE); | |
7796 | } | |
7797 | if (need_serialize) | |
7798 | spin_unlock(&balancing); | |
7799 | out: | |
7800 | if (time_after(next_balance, sd->last_balance + interval)) { | |
7801 | next_balance = sd->last_balance + interval; | |
7802 | update_next_balance = 1; | |
7803 | } | |
7804 | } | |
7805 | if (need_decay) { | |
7806 | /* | |
7807 | * Ensure the rq-wide value also decays but keep it at a | |
7808 | * reasonable floor to avoid funnies with rq->avg_idle. | |
7809 | */ | |
7810 | rq->max_idle_balance_cost = | |
7811 | max((u64)sysctl_sched_migration_cost, max_cost); | |
7812 | } | |
7813 | rcu_read_unlock(); | |
7814 | ||
7815 | /* | |
7816 | * next_balance will be updated only when there is a need. | |
7817 | * When the cpu is attached to null domain for ex, it will not be | |
7818 | * updated. | |
7819 | */ | |
7820 | if (likely(update_next_balance)) | |
7821 | rq->next_balance = next_balance; | |
7822 | } | |
7823 | ||
7824 | #ifdef CONFIG_NO_HZ_COMMON | |
7825 | /* | |
7826 | * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the | |
7827 | * rebalancing for all the cpus for whom scheduler ticks are stopped. | |
7828 | */ | |
7829 | static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) | |
7830 | { | |
7831 | int this_cpu = this_rq->cpu; | |
7832 | struct rq *rq; | |
7833 | int balance_cpu; | |
7834 | ||
7835 | if (idle != CPU_IDLE || | |
7836 | !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu))) | |
7837 | goto end; | |
7838 | ||
7839 | for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { | |
7840 | if (balance_cpu == this_cpu || !idle_cpu(balance_cpu)) | |
7841 | continue; | |
7842 | ||
7843 | /* | |
7844 | * If this cpu gets work to do, stop the load balancing | |
7845 | * work being done for other cpus. Next load | |
7846 | * balancing owner will pick it up. | |
7847 | */ | |
7848 | if (need_resched()) | |
7849 | break; | |
7850 | ||
7851 | rq = cpu_rq(balance_cpu); | |
7852 | ||
7853 | /* | |
7854 | * If time for next balance is due, | |
7855 | * do the balance. | |
7856 | */ | |
7857 | if (time_after_eq(jiffies, rq->next_balance)) { | |
7858 | raw_spin_lock_irq(&rq->lock); | |
7859 | update_rq_clock(rq); | |
7860 | update_idle_cpu_load(rq); | |
7861 | raw_spin_unlock_irq(&rq->lock); | |
7862 | rebalance_domains(rq, CPU_IDLE); | |
7863 | } | |
7864 | ||
7865 | if (time_after(this_rq->next_balance, rq->next_balance)) | |
7866 | this_rq->next_balance = rq->next_balance; | |
7867 | } | |
7868 | nohz.next_balance = this_rq->next_balance; | |
7869 | end: | |
7870 | clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)); | |
7871 | } | |
7872 | ||
7873 | /* | |
7874 | * Current heuristic for kicking the idle load balancer in the presence | |
7875 | * of an idle cpu in the system. | |
7876 | * - This rq has more than one task. | |
7877 | * - This rq has at least one CFS task and the capacity of the CPU is | |
7878 | * significantly reduced because of RT tasks or IRQs. | |
7879 | * - At parent of LLC scheduler domain level, this cpu's scheduler group has | |
7880 | * multiple busy cpu. | |
7881 | * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler | |
7882 | * domain span are idle. | |
7883 | */ | |
7884 | static inline bool nohz_kick_needed(struct rq *rq) | |
7885 | { | |
7886 | unsigned long now = jiffies; | |
7887 | struct sched_domain *sd; | |
7888 | struct sched_group_capacity *sgc; | |
7889 | int nr_busy, cpu = rq->cpu; | |
7890 | bool kick = false; | |
7891 | ||
7892 | if (unlikely(rq->idle_balance)) | |
7893 | return false; | |
7894 | ||
7895 | /* | |
7896 | * We may be recently in ticked or tickless idle mode. At the first | |
7897 | * busy tick after returning from idle, we will update the busy stats. | |
7898 | */ | |
7899 | set_cpu_sd_state_busy(); | |
7900 | nohz_balance_exit_idle(cpu); | |
7901 | ||
7902 | /* | |
7903 | * None are in tickless mode and hence no need for NOHZ idle load | |
7904 | * balancing. | |
7905 | */ | |
7906 | if (likely(!atomic_read(&nohz.nr_cpus))) | |
7907 | return false; | |
7908 | ||
7909 | if (time_before(now, nohz.next_balance)) | |
7910 | return false; | |
7911 | ||
7912 | if (rq->nr_running >= 2) | |
7913 | return true; | |
7914 | ||
7915 | rcu_read_lock(); | |
7916 | sd = rcu_dereference(per_cpu(sd_busy, cpu)); | |
7917 | if (sd) { | |
7918 | sgc = sd->groups->sgc; | |
7919 | nr_busy = atomic_read(&sgc->nr_busy_cpus); | |
7920 | ||
7921 | if (nr_busy > 1) { | |
7922 | kick = true; | |
7923 | goto unlock; | |
7924 | } | |
7925 | ||
7926 | } | |
7927 | ||
7928 | sd = rcu_dereference(rq->sd); | |
7929 | if (sd) { | |
7930 | if ((rq->cfs.h_nr_running >= 1) && | |
7931 | check_cpu_capacity(rq, sd)) { | |
7932 | kick = true; | |
7933 | goto unlock; | |
7934 | } | |
7935 | } | |
7936 | ||
7937 | sd = rcu_dereference(per_cpu(sd_asym, cpu)); | |
7938 | if (sd && (cpumask_first_and(nohz.idle_cpus_mask, | |
7939 | sched_domain_span(sd)) < cpu)) { | |
7940 | kick = true; | |
7941 | goto unlock; | |
7942 | } | |
7943 | ||
7944 | unlock: | |
7945 | rcu_read_unlock(); | |
7946 | return kick; | |
7947 | } | |
7948 | #else | |
7949 | static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { } | |
7950 | #endif | |
7951 | ||
7952 | /* | |
7953 | * run_rebalance_domains is triggered when needed from the scheduler tick. | |
7954 | * Also triggered for nohz idle balancing (with nohz_balancing_kick set). | |
7955 | */ | |
7956 | static void run_rebalance_domains(struct softirq_action *h) | |
7957 | { | |
7958 | struct rq *this_rq = this_rq(); | |
7959 | enum cpu_idle_type idle = this_rq->idle_balance ? | |
7960 | CPU_IDLE : CPU_NOT_IDLE; | |
7961 | ||
7962 | /* | |
7963 | * If this cpu has a pending nohz_balance_kick, then do the | |
7964 | * balancing on behalf of the other idle cpus whose ticks are | |
7965 | * stopped. Do nohz_idle_balance *before* rebalance_domains to | |
7966 | * give the idle cpus a chance to load balance. Else we may | |
7967 | * load balance only within the local sched_domain hierarchy | |
7968 | * and abort nohz_idle_balance altogether if we pull some load. | |
7969 | */ | |
7970 | nohz_idle_balance(this_rq, idle); | |
7971 | rebalance_domains(this_rq, idle); | |
7972 | } | |
7973 | ||
7974 | /* | |
7975 | * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. | |
7976 | */ | |
7977 | void trigger_load_balance(struct rq *rq) | |
7978 | { | |
7979 | /* Don't need to rebalance while attached to NULL domain */ | |
7980 | if (unlikely(on_null_domain(rq))) | |
7981 | return; | |
7982 | ||
7983 | if (time_after_eq(jiffies, rq->next_balance)) | |
7984 | raise_softirq(SCHED_SOFTIRQ); | |
7985 | #ifdef CONFIG_NO_HZ_COMMON | |
7986 | if (nohz_kick_needed(rq)) | |
7987 | nohz_balancer_kick(); | |
7988 | #endif | |
7989 | } | |
7990 | ||
7991 | static void rq_online_fair(struct rq *rq) | |
7992 | { | |
7993 | update_sysctl(); | |
7994 | ||
7995 | update_runtime_enabled(rq); | |
7996 | } | |
7997 | ||
7998 | static void rq_offline_fair(struct rq *rq) | |
7999 | { | |
8000 | update_sysctl(); | |
8001 | ||
8002 | /* Ensure any throttled groups are reachable by pick_next_task */ | |
8003 | unthrottle_offline_cfs_rqs(rq); | |
8004 | } | |
8005 | ||
8006 | #endif /* CONFIG_SMP */ | |
8007 | ||
8008 | /* | |
8009 | * scheduler tick hitting a task of our scheduling class: | |
8010 | */ | |
8011 | static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) | |
8012 | { | |
8013 | struct cfs_rq *cfs_rq; | |
8014 | struct sched_entity *se = &curr->se; | |
8015 | ||
8016 | for_each_sched_entity(se) { | |
8017 | cfs_rq = cfs_rq_of(se); | |
8018 | entity_tick(cfs_rq, se, queued); | |
8019 | } | |
8020 | ||
8021 | if (numabalancing_enabled) | |
8022 | task_tick_numa(rq, curr); | |
8023 | ||
8024 | update_rq_runnable_avg(rq, 1); | |
8025 | } | |
8026 | ||
8027 | /* | |
8028 | * called on fork with the child task as argument from the parent's context | |
8029 | * - child not yet on the tasklist | |
8030 | * - preemption disabled | |
8031 | */ | |
8032 | static void task_fork_fair(struct task_struct *p) | |
8033 | { | |
8034 | struct cfs_rq *cfs_rq; | |
8035 | struct sched_entity *se = &p->se, *curr; | |
8036 | int this_cpu = smp_processor_id(); | |
8037 | struct rq *rq = this_rq(); | |
8038 | unsigned long flags; | |
8039 | ||
8040 | raw_spin_lock_irqsave(&rq->lock, flags); | |
8041 | ||
8042 | update_rq_clock(rq); | |
8043 | ||
8044 | cfs_rq = task_cfs_rq(current); | |
8045 | curr = cfs_rq->curr; | |
8046 | ||
8047 | /* | |
8048 | * Not only the cpu but also the task_group of the parent might have | |
8049 | * been changed after parent->se.parent,cfs_rq were copied to | |
8050 | * child->se.parent,cfs_rq. So call __set_task_cpu() to make those | |
8051 | * of child point to valid ones. | |
8052 | */ | |
8053 | rcu_read_lock(); | |
8054 | __set_task_cpu(p, this_cpu); | |
8055 | rcu_read_unlock(); | |
8056 | ||
8057 | update_curr(cfs_rq); | |
8058 | ||
8059 | if (curr) | |
8060 | se->vruntime = curr->vruntime; | |
8061 | place_entity(cfs_rq, se, 1); | |
8062 | ||
8063 | if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { | |
8064 | /* | |
8065 | * Upon rescheduling, sched_class::put_prev_task() will place | |
8066 | * 'current' within the tree based on its new key value. | |
8067 | */ | |
8068 | swap(curr->vruntime, se->vruntime); | |
8069 | resched_curr(rq); | |
8070 | } | |
8071 | ||
8072 | se->vruntime -= cfs_rq->min_vruntime; | |
8073 | ||
8074 | raw_spin_unlock_irqrestore(&rq->lock, flags); | |
8075 | } | |
8076 | ||
8077 | /* | |
8078 | * Priority of the task has changed. Check to see if we preempt | |
8079 | * the current task. | |
8080 | */ | |
8081 | static void | |
8082 | prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) | |
8083 | { | |
8084 | if (!task_on_rq_queued(p)) | |
8085 | return; | |
8086 | ||
8087 | /* | |
8088 | * Reschedule if we are currently running on this runqueue and | |
8089 | * our priority decreased, or if we are not currently running on | |
8090 | * this runqueue and our priority is higher than the current's | |
8091 | */ | |
8092 | if (rq->curr == p) { | |
8093 | if (p->prio > oldprio) | |
8094 | resched_curr(rq); | |
8095 | } else | |
8096 | check_preempt_curr(rq, p, 0); | |
8097 | } | |
8098 | ||
8099 | static void switched_from_fair(struct rq *rq, struct task_struct *p) | |
8100 | { | |
8101 | struct sched_entity *se = &p->se; | |
8102 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
8103 | ||
8104 | /* | |
8105 | * Ensure the task's vruntime is normalized, so that when it's | |
8106 | * switched back to the fair class the enqueue_entity(.flags=0) will | |
8107 | * do the right thing. | |
8108 | * | |
8109 | * If it's queued, then the dequeue_entity(.flags=0) will already | |
8110 | * have normalized the vruntime, if it's !queued, then only when | |
8111 | * the task is sleeping will it still have non-normalized vruntime. | |
8112 | */ | |
8113 | if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) { | |
8114 | /* | |
8115 | * Fix up our vruntime so that the current sleep doesn't | |
8116 | * cause 'unlimited' sleep bonus. | |
8117 | */ | |
8118 | place_entity(cfs_rq, se, 0); | |
8119 | se->vruntime -= cfs_rq->min_vruntime; | |
8120 | } | |
8121 | ||
8122 | #ifdef CONFIG_SMP | |
8123 | /* | |
8124 | * Remove our load from contribution when we leave sched_fair | |
8125 | * and ensure we don't carry in an old decay_count if we | |
8126 | * switch back. | |
8127 | */ | |
8128 | if (se->avg.decay_count) { | |
8129 | __synchronize_entity_decay(se); | |
8130 | subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib); | |
8131 | } | |
8132 | #endif | |
8133 | } | |
8134 | ||
8135 | /* | |
8136 | * We switched to the sched_fair class. | |
8137 | */ | |
8138 | static void switched_to_fair(struct rq *rq, struct task_struct *p) | |
8139 | { | |
8140 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
8141 | struct sched_entity *se = &p->se; | |
8142 | /* | |
8143 | * Since the real-depth could have been changed (only FAIR | |
8144 | * class maintain depth value), reset depth properly. | |
8145 | */ | |
8146 | se->depth = se->parent ? se->parent->depth + 1 : 0; | |
8147 | #endif | |
8148 | if (!task_on_rq_queued(p)) | |
8149 | return; | |
8150 | ||
8151 | /* | |
8152 | * We were most likely switched from sched_rt, so | |
8153 | * kick off the schedule if running, otherwise just see | |
8154 | * if we can still preempt the current task. | |
8155 | */ | |
8156 | if (rq->curr == p) | |
8157 | resched_curr(rq); | |
8158 | else | |
8159 | check_preempt_curr(rq, p, 0); | |
8160 | } | |
8161 | ||
8162 | /* Account for a task changing its policy or group. | |
8163 | * | |
8164 | * This routine is mostly called to set cfs_rq->curr field when a task | |
8165 | * migrates between groups/classes. | |
8166 | */ | |
8167 | static void set_curr_task_fair(struct rq *rq) | |
8168 | { | |
8169 | struct sched_entity *se = &rq->curr->se; | |
8170 | ||
8171 | for_each_sched_entity(se) { | |
8172 | struct cfs_rq *cfs_rq = cfs_rq_of(se); | |
8173 | ||
8174 | set_next_entity(cfs_rq, se); | |
8175 | /* ensure bandwidth has been allocated on our new cfs_rq */ | |
8176 | account_cfs_rq_runtime(cfs_rq, 0); | |
8177 | } | |
8178 | } | |
8179 | ||
8180 | void init_cfs_rq(struct cfs_rq *cfs_rq) | |
8181 | { | |
8182 | cfs_rq->tasks_timeline = RB_ROOT; | |
8183 | cfs_rq->min_vruntime = (u64)(-(1LL << 20)); | |
8184 | #ifndef CONFIG_64BIT | |
8185 | cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; | |
8186 | #endif | |
8187 | #ifdef CONFIG_SMP | |
8188 | atomic64_set(&cfs_rq->decay_counter, 1); | |
8189 | atomic_long_set(&cfs_rq->removed_load, 0); | |
8190 | #endif | |
8191 | } | |
8192 | ||
8193 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
8194 | static void task_move_group_fair(struct task_struct *p, int queued) | |
8195 | { | |
8196 | struct sched_entity *se = &p->se; | |
8197 | struct cfs_rq *cfs_rq; | |
8198 | ||
8199 | /* | |
8200 | * If the task was not on the rq at the time of this cgroup movement | |
8201 | * it must have been asleep, sleeping tasks keep their ->vruntime | |
8202 | * absolute on their old rq until wakeup (needed for the fair sleeper | |
8203 | * bonus in place_entity()). | |
8204 | * | |
8205 | * If it was on the rq, we've just 'preempted' it, which does convert | |
8206 | * ->vruntime to a relative base. | |
8207 | * | |
8208 | * Make sure both cases convert their relative position when migrating | |
8209 | * to another cgroup's rq. This does somewhat interfere with the | |
8210 | * fair sleeper stuff for the first placement, but who cares. | |
8211 | */ | |
8212 | /* | |
8213 | * When !queued, vruntime of the task has usually NOT been normalized. | |
8214 | * But there are some cases where it has already been normalized: | |
8215 | * | |
8216 | * - Moving a forked child which is waiting for being woken up by | |
8217 | * wake_up_new_task(). | |
8218 | * - Moving a task which has been woken up by try_to_wake_up() and | |
8219 | * waiting for actually being woken up by sched_ttwu_pending(). | |
8220 | * | |
8221 | * To prevent boost or penalty in the new cfs_rq caused by delta | |
8222 | * min_vruntime between the two cfs_rqs, we skip vruntime adjustment. | |
8223 | */ | |
8224 | if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING)) | |
8225 | queued = 1; | |
8226 | ||
8227 | if (!queued) | |
8228 | se->vruntime -= cfs_rq_of(se)->min_vruntime; | |
8229 | set_task_rq(p, task_cpu(p)); | |
8230 | se->depth = se->parent ? se->parent->depth + 1 : 0; | |
8231 | if (!queued) { | |
8232 | cfs_rq = cfs_rq_of(se); | |
8233 | se->vruntime += cfs_rq->min_vruntime; | |
8234 | #ifdef CONFIG_SMP | |
8235 | /* | |
8236 | * migrate_task_rq_fair() will have removed our previous | |
8237 | * contribution, but we must synchronize for ongoing future | |
8238 | * decay. | |
8239 | */ | |
8240 | se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter); | |
8241 | cfs_rq->blocked_load_avg += se->avg.load_avg_contrib; | |
8242 | #endif | |
8243 | } | |
8244 | } | |
8245 | ||
8246 | void free_fair_sched_group(struct task_group *tg) | |
8247 | { | |
8248 | int i; | |
8249 | ||
8250 | destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); | |
8251 | ||
8252 | for_each_possible_cpu(i) { | |
8253 | if (tg->cfs_rq) | |
8254 | kfree(tg->cfs_rq[i]); | |
8255 | if (tg->se) | |
8256 | kfree(tg->se[i]); | |
8257 | } | |
8258 | ||
8259 | kfree(tg->cfs_rq); | |
8260 | kfree(tg->se); | |
8261 | } | |
8262 | ||
8263 | int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) | |
8264 | { | |
8265 | struct cfs_rq *cfs_rq; | |
8266 | struct sched_entity *se; | |
8267 | int i; | |
8268 | ||
8269 | tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL); | |
8270 | if (!tg->cfs_rq) | |
8271 | goto err; | |
8272 | tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL); | |
8273 | if (!tg->se) | |
8274 | goto err; | |
8275 | ||
8276 | tg->shares = NICE_0_LOAD; | |
8277 | ||
8278 | init_cfs_bandwidth(tg_cfs_bandwidth(tg)); | |
8279 | ||
8280 | for_each_possible_cpu(i) { | |
8281 | cfs_rq = kzalloc_node(sizeof(struct cfs_rq), | |
8282 | GFP_KERNEL, cpu_to_node(i)); | |
8283 | if (!cfs_rq) | |
8284 | goto err; | |
8285 | ||
8286 | se = kzalloc_node(sizeof(struct sched_entity), | |
8287 | GFP_KERNEL, cpu_to_node(i)); | |
8288 | if (!se) | |
8289 | goto err_free_rq; | |
8290 | ||
8291 | init_cfs_rq(cfs_rq); | |
8292 | init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); | |
8293 | } | |
8294 | ||
8295 | return 1; | |
8296 | ||
8297 | err_free_rq: | |
8298 | kfree(cfs_rq); | |
8299 | err: | |
8300 | return 0; | |
8301 | } | |
8302 | ||
8303 | void unregister_fair_sched_group(struct task_group *tg, int cpu) | |
8304 | { | |
8305 | struct rq *rq = cpu_rq(cpu); | |
8306 | unsigned long flags; | |
8307 | ||
8308 | /* | |
8309 | * Only empty task groups can be destroyed; so we can speculatively | |
8310 | * check on_list without danger of it being re-added. | |
8311 | */ | |
8312 | if (!tg->cfs_rq[cpu]->on_list) | |
8313 | return; | |
8314 | ||
8315 | raw_spin_lock_irqsave(&rq->lock, flags); | |
8316 | list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); | |
8317 | raw_spin_unlock_irqrestore(&rq->lock, flags); | |
8318 | } | |
8319 | ||
8320 | void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, | |
8321 | struct sched_entity *se, int cpu, | |
8322 | struct sched_entity *parent) | |
8323 | { | |
8324 | struct rq *rq = cpu_rq(cpu); | |
8325 | ||
8326 | cfs_rq->tg = tg; | |
8327 | cfs_rq->rq = rq; | |
8328 | init_cfs_rq_runtime(cfs_rq); | |
8329 | ||
8330 | tg->cfs_rq[cpu] = cfs_rq; | |
8331 | tg->se[cpu] = se; | |
8332 | ||
8333 | /* se could be NULL for root_task_group */ | |
8334 | if (!se) | |
8335 | return; | |
8336 | ||
8337 | if (!parent) { | |
8338 | se->cfs_rq = &rq->cfs; | |
8339 | se->depth = 0; | |
8340 | } else { | |
8341 | se->cfs_rq = parent->my_q; | |
8342 | se->depth = parent->depth + 1; | |
8343 | } | |
8344 | ||
8345 | se->my_q = cfs_rq; | |
8346 | /* guarantee group entities always have weight */ | |
8347 | update_load_set(&se->load, NICE_0_LOAD); | |
8348 | se->parent = parent; | |
8349 | } | |
8350 | ||
8351 | static DEFINE_MUTEX(shares_mutex); | |
8352 | ||
8353 | int sched_group_set_shares(struct task_group *tg, unsigned long shares) | |
8354 | { | |
8355 | int i; | |
8356 | unsigned long flags; | |
8357 | ||
8358 | /* | |
8359 | * We can't change the weight of the root cgroup. | |
8360 | */ | |
8361 | if (!tg->se[0]) | |
8362 | return -EINVAL; | |
8363 | ||
8364 | shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); | |
8365 | ||
8366 | mutex_lock(&shares_mutex); | |
8367 | if (tg->shares == shares) | |
8368 | goto done; | |
8369 | ||
8370 | tg->shares = shares; | |
8371 | for_each_possible_cpu(i) { | |
8372 | struct rq *rq = cpu_rq(i); | |
8373 | struct sched_entity *se; | |
8374 | ||
8375 | se = tg->se[i]; | |
8376 | /* Propagate contribution to hierarchy */ | |
8377 | raw_spin_lock_irqsave(&rq->lock, flags); | |
8378 | ||
8379 | /* Possible calls to update_curr() need rq clock */ | |
8380 | update_rq_clock(rq); | |
8381 | for_each_sched_entity(se) | |
8382 | update_cfs_shares(group_cfs_rq(se)); | |
8383 | raw_spin_unlock_irqrestore(&rq->lock, flags); | |
8384 | } | |
8385 | ||
8386 | done: | |
8387 | mutex_unlock(&shares_mutex); | |
8388 | return 0; | |
8389 | } | |
8390 | #else /* CONFIG_FAIR_GROUP_SCHED */ | |
8391 | ||
8392 | void free_fair_sched_group(struct task_group *tg) { } | |
8393 | ||
8394 | int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) | |
8395 | { | |
8396 | return 1; | |
8397 | } | |
8398 | ||
8399 | void unregister_fair_sched_group(struct task_group *tg, int cpu) { } | |
8400 | ||
8401 | #endif /* CONFIG_FAIR_GROUP_SCHED */ | |
8402 | ||
8403 | ||
8404 | static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) | |
8405 | { | |
8406 | struct sched_entity *se = &task->se; | |
8407 | unsigned int rr_interval = 0; | |
8408 | ||
8409 | /* | |
8410 | * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise | |
8411 | * idle runqueue: | |
8412 | */ | |
8413 | if (rq->cfs.load.weight) | |
8414 | rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se)); | |
8415 | ||
8416 | return rr_interval; | |
8417 | } | |
8418 | ||
8419 | /* | |
8420 | * All the scheduling class methods: | |
8421 | */ | |
8422 | const struct sched_class fair_sched_class = { | |
8423 | .next = &idle_sched_class, | |
8424 | .enqueue_task = enqueue_task_fair, | |
8425 | .dequeue_task = dequeue_task_fair, | |
8426 | .yield_task = yield_task_fair, | |
8427 | .yield_to_task = yield_to_task_fair, | |
8428 | ||
8429 | .check_preempt_curr = check_preempt_wakeup, | |
8430 | ||
8431 | .pick_next_task = pick_next_task_fair, | |
8432 | .put_prev_task = put_prev_task_fair, | |
8433 | ||
8434 | #ifdef CONFIG_SMP | |
8435 | .select_task_rq = select_task_rq_fair, | |
8436 | .migrate_task_rq = migrate_task_rq_fair, | |
8437 | ||
8438 | .rq_online = rq_online_fair, | |
8439 | .rq_offline = rq_offline_fair, | |
8440 | ||
8441 | .task_waking = task_waking_fair, | |
8442 | #endif | |
8443 | ||
8444 | .set_curr_task = set_curr_task_fair, | |
8445 | .task_tick = task_tick_fair, | |
8446 | .task_fork = task_fork_fair, | |
8447 | ||
8448 | .prio_changed = prio_changed_fair, | |
8449 | .switched_from = switched_from_fair, | |
8450 | .switched_to = switched_to_fair, | |
8451 | ||
8452 | .get_rr_interval = get_rr_interval_fair, | |
8453 | ||
8454 | .update_curr = update_curr_fair, | |
8455 | ||
8456 | #ifdef CONFIG_FAIR_GROUP_SCHED | |
8457 | .task_move_group = task_move_group_fair, | |
8458 | #endif | |
8459 | }; | |
8460 | ||
8461 | #ifdef CONFIG_SCHED_DEBUG | |
8462 | void print_cfs_stats(struct seq_file *m, int cpu) | |
8463 | { | |
8464 | struct cfs_rq *cfs_rq; | |
8465 | ||
8466 | rcu_read_lock(); | |
8467 | for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) | |
8468 | print_cfs_rq(m, cpu, cfs_rq); | |
8469 | rcu_read_unlock(); | |
8470 | } | |
8471 | #endif | |
8472 | ||
8473 | __init void init_sched_fair_class(void) | |
8474 | { | |
8475 | #ifdef CONFIG_SMP | |
8476 | open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); | |
8477 | ||
8478 | #ifdef CONFIG_NO_HZ_COMMON | |
8479 | nohz.next_balance = jiffies; | |
8480 | zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); | |
8481 | cpu_notifier(sched_ilb_notifier, 0); | |
8482 | #endif | |
8483 | #endif /* SMP */ | |
8484 | ||
8485 | } |