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