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1 | /* | |
2 | * Interface for controlling IO bandwidth on a request queue | |
3 | * | |
4 | * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com> | |
5 | */ | |
6 | ||
7 | #include <linux/module.h> | |
8 | #include <linux/slab.h> | |
9 | #include <linux/blkdev.h> | |
10 | #include <linux/bio.h> | |
11 | #include <linux/blktrace_api.h> | |
12 | #include "blk-cgroup.h" | |
13 | #include "blk.h" | |
14 | ||
15 | /* Max dispatch from a group in 1 round */ | |
16 | static int throtl_grp_quantum = 8; | |
17 | ||
18 | /* Total max dispatch from all groups in one round */ | |
19 | static int throtl_quantum = 32; | |
20 | ||
21 | /* Throttling is performed over 100ms slice and after that slice is renewed */ | |
22 | static unsigned long throtl_slice = HZ/10; /* 100 ms */ | |
23 | ||
24 | /* A workqueue to queue throttle related work */ | |
25 | static struct workqueue_struct *kthrotld_workqueue; | |
26 | static void throtl_schedule_delayed_work(struct throtl_data *td, | |
27 | unsigned long delay); | |
28 | ||
29 | struct throtl_rb_root { | |
30 | struct rb_root rb; | |
31 | struct rb_node *left; | |
32 | unsigned int count; | |
33 | unsigned long min_disptime; | |
34 | }; | |
35 | ||
36 | #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \ | |
37 | .count = 0, .min_disptime = 0} | |
38 | ||
39 | #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node) | |
40 | ||
41 | struct throtl_grp { | |
42 | /* List of throtl groups on the request queue*/ | |
43 | struct hlist_node tg_node; | |
44 | ||
45 | /* active throtl group service_tree member */ | |
46 | struct rb_node rb_node; | |
47 | ||
48 | /* | |
49 | * Dispatch time in jiffies. This is the estimated time when group | |
50 | * will unthrottle and is ready to dispatch more bio. It is used as | |
51 | * key to sort active groups in service tree. | |
52 | */ | |
53 | unsigned long disptime; | |
54 | ||
55 | struct blkio_group blkg; | |
56 | atomic_t ref; | |
57 | unsigned int flags; | |
58 | ||
59 | /* Two lists for READ and WRITE */ | |
60 | struct bio_list bio_lists[2]; | |
61 | ||
62 | /* Number of queued bios on READ and WRITE lists */ | |
63 | unsigned int nr_queued[2]; | |
64 | ||
65 | /* bytes per second rate limits */ | |
66 | uint64_t bps[2]; | |
67 | ||
68 | /* IOPS limits */ | |
69 | unsigned int iops[2]; | |
70 | ||
71 | /* Number of bytes disptached in current slice */ | |
72 | uint64_t bytes_disp[2]; | |
73 | /* Number of bio's dispatched in current slice */ | |
74 | unsigned int io_disp[2]; | |
75 | ||
76 | /* When did we start a new slice */ | |
77 | unsigned long slice_start[2]; | |
78 | unsigned long slice_end[2]; | |
79 | ||
80 | /* Some throttle limits got updated for the group */ | |
81 | int limits_changed; | |
82 | ||
83 | struct rcu_head rcu_head; | |
84 | }; | |
85 | ||
86 | struct throtl_data | |
87 | { | |
88 | /* List of throtl groups */ | |
89 | struct hlist_head tg_list; | |
90 | ||
91 | /* service tree for active throtl groups */ | |
92 | struct throtl_rb_root tg_service_tree; | |
93 | ||
94 | struct throtl_grp *root_tg; | |
95 | struct request_queue *queue; | |
96 | ||
97 | /* Total Number of queued bios on READ and WRITE lists */ | |
98 | unsigned int nr_queued[2]; | |
99 | ||
100 | /* | |
101 | * number of total undestroyed groups | |
102 | */ | |
103 | unsigned int nr_undestroyed_grps; | |
104 | ||
105 | /* Work for dispatching throttled bios */ | |
106 | struct delayed_work throtl_work; | |
107 | ||
108 | int limits_changed; | |
109 | }; | |
110 | ||
111 | enum tg_state_flags { | |
112 | THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */ | |
113 | }; | |
114 | ||
115 | #define THROTL_TG_FNS(name) \ | |
116 | static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \ | |
117 | { \ | |
118 | (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \ | |
119 | } \ | |
120 | static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \ | |
121 | { \ | |
122 | (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \ | |
123 | } \ | |
124 | static inline int throtl_tg_##name(const struct throtl_grp *tg) \ | |
125 | { \ | |
126 | return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \ | |
127 | } | |
128 | ||
129 | THROTL_TG_FNS(on_rr); | |
130 | ||
131 | #define throtl_log_tg(td, tg, fmt, args...) \ | |
132 | blk_add_trace_msg((td)->queue, "throtl %s " fmt, \ | |
133 | blkg_path(&(tg)->blkg), ##args); \ | |
134 | ||
135 | #define throtl_log(td, fmt, args...) \ | |
136 | blk_add_trace_msg((td)->queue, "throtl " fmt, ##args) | |
137 | ||
138 | static inline struct throtl_grp *tg_of_blkg(struct blkio_group *blkg) | |
139 | { | |
140 | if (blkg) | |
141 | return container_of(blkg, struct throtl_grp, blkg); | |
142 | ||
143 | return NULL; | |
144 | } | |
145 | ||
146 | static inline unsigned int total_nr_queued(struct throtl_data *td) | |
147 | { | |
148 | return td->nr_queued[0] + td->nr_queued[1]; | |
149 | } | |
150 | ||
151 | static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg) | |
152 | { | |
153 | atomic_inc(&tg->ref); | |
154 | return tg; | |
155 | } | |
156 | ||
157 | static void throtl_free_tg(struct rcu_head *head) | |
158 | { | |
159 | struct throtl_grp *tg; | |
160 | ||
161 | tg = container_of(head, struct throtl_grp, rcu_head); | |
162 | free_percpu(tg->blkg.stats_cpu); | |
163 | kfree(tg); | |
164 | } | |
165 | ||
166 | static void throtl_put_tg(struct throtl_grp *tg) | |
167 | { | |
168 | BUG_ON(atomic_read(&tg->ref) <= 0); | |
169 | if (!atomic_dec_and_test(&tg->ref)) | |
170 | return; | |
171 | ||
172 | /* | |
173 | * A group is freed in rcu manner. But having an rcu lock does not | |
174 | * mean that one can access all the fields of blkg and assume these | |
175 | * are valid. For example, don't try to follow throtl_data and | |
176 | * request queue links. | |
177 | * | |
178 | * Having a reference to blkg under an rcu allows acess to only | |
179 | * values local to groups like group stats and group rate limits | |
180 | */ | |
181 | call_rcu(&tg->rcu_head, throtl_free_tg); | |
182 | } | |
183 | ||
184 | static void throtl_init_group(struct throtl_grp *tg) | |
185 | { | |
186 | INIT_HLIST_NODE(&tg->tg_node); | |
187 | RB_CLEAR_NODE(&tg->rb_node); | |
188 | bio_list_init(&tg->bio_lists[0]); | |
189 | bio_list_init(&tg->bio_lists[1]); | |
190 | tg->limits_changed = false; | |
191 | ||
192 | /* Practically unlimited BW */ | |
193 | tg->bps[0] = tg->bps[1] = -1; | |
194 | tg->iops[0] = tg->iops[1] = -1; | |
195 | ||
196 | /* | |
197 | * Take the initial reference that will be released on destroy | |
198 | * This can be thought of a joint reference by cgroup and | |
199 | * request queue which will be dropped by either request queue | |
200 | * exit or cgroup deletion path depending on who is exiting first. | |
201 | */ | |
202 | atomic_set(&tg->ref, 1); | |
203 | } | |
204 | ||
205 | /* Should be called with rcu read lock held (needed for blkcg) */ | |
206 | static void | |
207 | throtl_add_group_to_td_list(struct throtl_data *td, struct throtl_grp *tg) | |
208 | { | |
209 | hlist_add_head(&tg->tg_node, &td->tg_list); | |
210 | td->nr_undestroyed_grps++; | |
211 | } | |
212 | ||
213 | static void | |
214 | __throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg) | |
215 | { | |
216 | struct backing_dev_info *bdi = &td->queue->backing_dev_info; | |
217 | unsigned int major, minor; | |
218 | ||
219 | if (!tg || tg->blkg.dev) | |
220 | return; | |
221 | ||
222 | /* | |
223 | * Fill in device details for a group which might not have been | |
224 | * filled at group creation time as queue was being instantiated | |
225 | * and driver had not attached a device yet | |
226 | */ | |
227 | if (bdi->dev && dev_name(bdi->dev)) { | |
228 | sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); | |
229 | tg->blkg.dev = MKDEV(major, minor); | |
230 | } | |
231 | } | |
232 | ||
233 | /* | |
234 | * Should be called with without queue lock held. Here queue lock will be | |
235 | * taken rarely. It will be taken only once during life time of a group | |
236 | * if need be | |
237 | */ | |
238 | static void | |
239 | throtl_tg_fill_dev_details(struct throtl_data *td, struct throtl_grp *tg) | |
240 | { | |
241 | if (!tg || tg->blkg.dev) | |
242 | return; | |
243 | ||
244 | spin_lock_irq(td->queue->queue_lock); | |
245 | __throtl_tg_fill_dev_details(td, tg); | |
246 | spin_unlock_irq(td->queue->queue_lock); | |
247 | } | |
248 | ||
249 | static void throtl_init_add_tg_lists(struct throtl_data *td, | |
250 | struct throtl_grp *tg, struct blkio_cgroup *blkcg) | |
251 | { | |
252 | __throtl_tg_fill_dev_details(td, tg); | |
253 | ||
254 | /* Add group onto cgroup list */ | |
255 | blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td, | |
256 | tg->blkg.dev, BLKIO_POLICY_THROTL); | |
257 | ||
258 | tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev); | |
259 | tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev); | |
260 | tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev); | |
261 | tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev); | |
262 | ||
263 | throtl_add_group_to_td_list(td, tg); | |
264 | } | |
265 | ||
266 | /* Should be called without queue lock and outside of rcu period */ | |
267 | static struct throtl_grp *throtl_alloc_tg(struct throtl_data *td) | |
268 | { | |
269 | struct throtl_grp *tg = NULL; | |
270 | int ret; | |
271 | ||
272 | tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node); | |
273 | if (!tg) | |
274 | return NULL; | |
275 | ||
276 | ret = blkio_alloc_blkg_stats(&tg->blkg); | |
277 | ||
278 | if (ret) { | |
279 | kfree(tg); | |
280 | return NULL; | |
281 | } | |
282 | ||
283 | throtl_init_group(tg); | |
284 | return tg; | |
285 | } | |
286 | ||
287 | static struct | |
288 | throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg) | |
289 | { | |
290 | struct throtl_grp *tg = NULL; | |
291 | void *key = td; | |
292 | ||
293 | /* | |
294 | * This is the common case when there are no blkio cgroups. | |
295 | * Avoid lookup in this case | |
296 | */ | |
297 | if (blkcg == &blkio_root_cgroup) | |
298 | tg = td->root_tg; | |
299 | else | |
300 | tg = tg_of_blkg(blkiocg_lookup_group(blkcg, key)); | |
301 | ||
302 | __throtl_tg_fill_dev_details(td, tg); | |
303 | return tg; | |
304 | } | |
305 | ||
306 | /* | |
307 | * This function returns with queue lock unlocked in case of error, like | |
308 | * request queue is no more | |
309 | */ | |
310 | static struct throtl_grp * throtl_get_tg(struct throtl_data *td) | |
311 | { | |
312 | struct throtl_grp *tg = NULL, *__tg = NULL; | |
313 | struct blkio_cgroup *blkcg; | |
314 | struct request_queue *q = td->queue; | |
315 | ||
316 | rcu_read_lock(); | |
317 | blkcg = task_blkio_cgroup(current); | |
318 | tg = throtl_find_tg(td, blkcg); | |
319 | if (tg) { | |
320 | rcu_read_unlock(); | |
321 | return tg; | |
322 | } | |
323 | ||
324 | /* | |
325 | * Need to allocate a group. Allocation of group also needs allocation | |
326 | * of per cpu stats which in-turn takes a mutex() and can block. Hence | |
327 | * we need to drop rcu lock and queue_lock before we call alloc. | |
328 | */ | |
329 | rcu_read_unlock(); | |
330 | spin_unlock_irq(q->queue_lock); | |
331 | ||
332 | tg = throtl_alloc_tg(td); | |
333 | /* | |
334 | * We might have slept in group allocation. Make sure queue is not | |
335 | * dead | |
336 | */ | |
337 | if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) { | |
338 | if (tg) | |
339 | kfree(tg); | |
340 | ||
341 | return ERR_PTR(-ENODEV); | |
342 | } | |
343 | ||
344 | /* Group allocated and queue is still alive. take the lock */ | |
345 | spin_lock_irq(q->queue_lock); | |
346 | ||
347 | /* | |
348 | * Initialize the new group. After sleeping, read the blkcg again. | |
349 | */ | |
350 | rcu_read_lock(); | |
351 | blkcg = task_blkio_cgroup(current); | |
352 | ||
353 | /* | |
354 | * If some other thread already allocated the group while we were | |
355 | * not holding queue lock, free up the group | |
356 | */ | |
357 | __tg = throtl_find_tg(td, blkcg); | |
358 | ||
359 | if (__tg) { | |
360 | kfree(tg); | |
361 | rcu_read_unlock(); | |
362 | return __tg; | |
363 | } | |
364 | ||
365 | /* Group allocation failed. Account the IO to root group */ | |
366 | if (!tg) { | |
367 | tg = td->root_tg; | |
368 | return tg; | |
369 | } | |
370 | ||
371 | throtl_init_add_tg_lists(td, tg, blkcg); | |
372 | rcu_read_unlock(); | |
373 | return tg; | |
374 | } | |
375 | ||
376 | static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root) | |
377 | { | |
378 | /* Service tree is empty */ | |
379 | if (!root->count) | |
380 | return NULL; | |
381 | ||
382 | if (!root->left) | |
383 | root->left = rb_first(&root->rb); | |
384 | ||
385 | if (root->left) | |
386 | return rb_entry_tg(root->left); | |
387 | ||
388 | return NULL; | |
389 | } | |
390 | ||
391 | static void rb_erase_init(struct rb_node *n, struct rb_root *root) | |
392 | { | |
393 | rb_erase(n, root); | |
394 | RB_CLEAR_NODE(n); | |
395 | } | |
396 | ||
397 | static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root) | |
398 | { | |
399 | if (root->left == n) | |
400 | root->left = NULL; | |
401 | rb_erase_init(n, &root->rb); | |
402 | --root->count; | |
403 | } | |
404 | ||
405 | static void update_min_dispatch_time(struct throtl_rb_root *st) | |
406 | { | |
407 | struct throtl_grp *tg; | |
408 | ||
409 | tg = throtl_rb_first(st); | |
410 | if (!tg) | |
411 | return; | |
412 | ||
413 | st->min_disptime = tg->disptime; | |
414 | } | |
415 | ||
416 | static void | |
417 | tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg) | |
418 | { | |
419 | struct rb_node **node = &st->rb.rb_node; | |
420 | struct rb_node *parent = NULL; | |
421 | struct throtl_grp *__tg; | |
422 | unsigned long key = tg->disptime; | |
423 | int left = 1; | |
424 | ||
425 | while (*node != NULL) { | |
426 | parent = *node; | |
427 | __tg = rb_entry_tg(parent); | |
428 | ||
429 | if (time_before(key, __tg->disptime)) | |
430 | node = &parent->rb_left; | |
431 | else { | |
432 | node = &parent->rb_right; | |
433 | left = 0; | |
434 | } | |
435 | } | |
436 | ||
437 | if (left) | |
438 | st->left = &tg->rb_node; | |
439 | ||
440 | rb_link_node(&tg->rb_node, parent, node); | |
441 | rb_insert_color(&tg->rb_node, &st->rb); | |
442 | } | |
443 | ||
444 | static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
445 | { | |
446 | struct throtl_rb_root *st = &td->tg_service_tree; | |
447 | ||
448 | tg_service_tree_add(st, tg); | |
449 | throtl_mark_tg_on_rr(tg); | |
450 | st->count++; | |
451 | } | |
452 | ||
453 | static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
454 | { | |
455 | if (!throtl_tg_on_rr(tg)) | |
456 | __throtl_enqueue_tg(td, tg); | |
457 | } | |
458 | ||
459 | static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
460 | { | |
461 | throtl_rb_erase(&tg->rb_node, &td->tg_service_tree); | |
462 | throtl_clear_tg_on_rr(tg); | |
463 | } | |
464 | ||
465 | static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) | |
466 | { | |
467 | if (throtl_tg_on_rr(tg)) | |
468 | __throtl_dequeue_tg(td, tg); | |
469 | } | |
470 | ||
471 | static void throtl_schedule_next_dispatch(struct throtl_data *td) | |
472 | { | |
473 | struct throtl_rb_root *st = &td->tg_service_tree; | |
474 | ||
475 | /* | |
476 | * If there are more bios pending, schedule more work. | |
477 | */ | |
478 | if (!total_nr_queued(td)) | |
479 | return; | |
480 | ||
481 | BUG_ON(!st->count); | |
482 | ||
483 | update_min_dispatch_time(st); | |
484 | ||
485 | if (time_before_eq(st->min_disptime, jiffies)) | |
486 | throtl_schedule_delayed_work(td, 0); | |
487 | else | |
488 | throtl_schedule_delayed_work(td, (st->min_disptime - jiffies)); | |
489 | } | |
490 | ||
491 | static inline void | |
492 | throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) | |
493 | { | |
494 | tg->bytes_disp[rw] = 0; | |
495 | tg->io_disp[rw] = 0; | |
496 | tg->slice_start[rw] = jiffies; | |
497 | tg->slice_end[rw] = jiffies + throtl_slice; | |
498 | throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu", | |
499 | rw == READ ? 'R' : 'W', tg->slice_start[rw], | |
500 | tg->slice_end[rw], jiffies); | |
501 | } | |
502 | ||
503 | static inline void throtl_set_slice_end(struct throtl_data *td, | |
504 | struct throtl_grp *tg, bool rw, unsigned long jiffy_end) | |
505 | { | |
506 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); | |
507 | } | |
508 | ||
509 | static inline void throtl_extend_slice(struct throtl_data *td, | |
510 | struct throtl_grp *tg, bool rw, unsigned long jiffy_end) | |
511 | { | |
512 | tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); | |
513 | throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu", | |
514 | rw == READ ? 'R' : 'W', tg->slice_start[rw], | |
515 | tg->slice_end[rw], jiffies); | |
516 | } | |
517 | ||
518 | /* Determine if previously allocated or extended slice is complete or not */ | |
519 | static bool | |
520 | throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw) | |
521 | { | |
522 | if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) | |
523 | return 0; | |
524 | ||
525 | return 1; | |
526 | } | |
527 | ||
528 | /* Trim the used slices and adjust slice start accordingly */ | |
529 | static inline void | |
530 | throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) | |
531 | { | |
532 | unsigned long nr_slices, time_elapsed, io_trim; | |
533 | u64 bytes_trim, tmp; | |
534 | ||
535 | BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])); | |
536 | ||
537 | /* | |
538 | * If bps are unlimited (-1), then time slice don't get | |
539 | * renewed. Don't try to trim the slice if slice is used. A new | |
540 | * slice will start when appropriate. | |
541 | */ | |
542 | if (throtl_slice_used(td, tg, rw)) | |
543 | return; | |
544 | ||
545 | /* | |
546 | * A bio has been dispatched. Also adjust slice_end. It might happen | |
547 | * that initially cgroup limit was very low resulting in high | |
548 | * slice_end, but later limit was bumped up and bio was dispached | |
549 | * sooner, then we need to reduce slice_end. A high bogus slice_end | |
550 | * is bad because it does not allow new slice to start. | |
551 | */ | |
552 | ||
553 | throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice); | |
554 | ||
555 | time_elapsed = jiffies - tg->slice_start[rw]; | |
556 | ||
557 | nr_slices = time_elapsed / throtl_slice; | |
558 | ||
559 | if (!nr_slices) | |
560 | return; | |
561 | tmp = tg->bps[rw] * throtl_slice * nr_slices; | |
562 | do_div(tmp, HZ); | |
563 | bytes_trim = tmp; | |
564 | ||
565 | io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ; | |
566 | ||
567 | if (!bytes_trim && !io_trim) | |
568 | return; | |
569 | ||
570 | if (tg->bytes_disp[rw] >= bytes_trim) | |
571 | tg->bytes_disp[rw] -= bytes_trim; | |
572 | else | |
573 | tg->bytes_disp[rw] = 0; | |
574 | ||
575 | if (tg->io_disp[rw] >= io_trim) | |
576 | tg->io_disp[rw] -= io_trim; | |
577 | else | |
578 | tg->io_disp[rw] = 0; | |
579 | ||
580 | tg->slice_start[rw] += nr_slices * throtl_slice; | |
581 | ||
582 | throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu" | |
583 | " start=%lu end=%lu jiffies=%lu", | |
584 | rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, | |
585 | tg->slice_start[rw], tg->slice_end[rw], jiffies); | |
586 | } | |
587 | ||
588 | static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, | |
589 | struct bio *bio, unsigned long *wait) | |
590 | { | |
591 | bool rw = bio_data_dir(bio); | |
592 | unsigned int io_allowed; | |
593 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; | |
594 | u64 tmp; | |
595 | ||
596 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; | |
597 | ||
598 | /* Slice has just started. Consider one slice interval */ | |
599 | if (!jiffy_elapsed) | |
600 | jiffy_elapsed_rnd = throtl_slice; | |
601 | ||
602 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); | |
603 | ||
604 | /* | |
605 | * jiffy_elapsed_rnd should not be a big value as minimum iops can be | |
606 | * 1 then at max jiffy elapsed should be equivalent of 1 second as we | |
607 | * will allow dispatch after 1 second and after that slice should | |
608 | * have been trimmed. | |
609 | */ | |
610 | ||
611 | tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; | |
612 | do_div(tmp, HZ); | |
613 | ||
614 | if (tmp > UINT_MAX) | |
615 | io_allowed = UINT_MAX; | |
616 | else | |
617 | io_allowed = tmp; | |
618 | ||
619 | if (tg->io_disp[rw] + 1 <= io_allowed) { | |
620 | if (wait) | |
621 | *wait = 0; | |
622 | return 1; | |
623 | } | |
624 | ||
625 | /* Calc approx time to dispatch */ | |
626 | jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1; | |
627 | ||
628 | if (jiffy_wait > jiffy_elapsed) | |
629 | jiffy_wait = jiffy_wait - jiffy_elapsed; | |
630 | else | |
631 | jiffy_wait = 1; | |
632 | ||
633 | if (wait) | |
634 | *wait = jiffy_wait; | |
635 | return 0; | |
636 | } | |
637 | ||
638 | static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg, | |
639 | struct bio *bio, unsigned long *wait) | |
640 | { | |
641 | bool rw = bio_data_dir(bio); | |
642 | u64 bytes_allowed, extra_bytes, tmp; | |
643 | unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; | |
644 | ||
645 | jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; | |
646 | ||
647 | /* Slice has just started. Consider one slice interval */ | |
648 | if (!jiffy_elapsed) | |
649 | jiffy_elapsed_rnd = throtl_slice; | |
650 | ||
651 | jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); | |
652 | ||
653 | tmp = tg->bps[rw] * jiffy_elapsed_rnd; | |
654 | do_div(tmp, HZ); | |
655 | bytes_allowed = tmp; | |
656 | ||
657 | if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) { | |
658 | if (wait) | |
659 | *wait = 0; | |
660 | return 1; | |
661 | } | |
662 | ||
663 | /* Calc approx time to dispatch */ | |
664 | extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed; | |
665 | jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]); | |
666 | ||
667 | if (!jiffy_wait) | |
668 | jiffy_wait = 1; | |
669 | ||
670 | /* | |
671 | * This wait time is without taking into consideration the rounding | |
672 | * up we did. Add that time also. | |
673 | */ | |
674 | jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); | |
675 | if (wait) | |
676 | *wait = jiffy_wait; | |
677 | return 0; | |
678 | } | |
679 | ||
680 | static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) { | |
681 | if (tg->bps[rw] == -1 && tg->iops[rw] == -1) | |
682 | return 1; | |
683 | return 0; | |
684 | } | |
685 | ||
686 | /* | |
687 | * Returns whether one can dispatch a bio or not. Also returns approx number | |
688 | * of jiffies to wait before this bio is with-in IO rate and can be dispatched | |
689 | */ | |
690 | static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, | |
691 | struct bio *bio, unsigned long *wait) | |
692 | { | |
693 | bool rw = bio_data_dir(bio); | |
694 | unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; | |
695 | ||
696 | /* | |
697 | * Currently whole state machine of group depends on first bio | |
698 | * queued in the group bio list. So one should not be calling | |
699 | * this function with a different bio if there are other bios | |
700 | * queued. | |
701 | */ | |
702 | BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw])); | |
703 | ||
704 | /* If tg->bps = -1, then BW is unlimited */ | |
705 | if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { | |
706 | if (wait) | |
707 | *wait = 0; | |
708 | return 1; | |
709 | } | |
710 | ||
711 | /* | |
712 | * If previous slice expired, start a new one otherwise renew/extend | |
713 | * existing slice to make sure it is at least throtl_slice interval | |
714 | * long since now. | |
715 | */ | |
716 | if (throtl_slice_used(td, tg, rw)) | |
717 | throtl_start_new_slice(td, tg, rw); | |
718 | else { | |
719 | if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) | |
720 | throtl_extend_slice(td, tg, rw, jiffies + throtl_slice); | |
721 | } | |
722 | ||
723 | if (tg_with_in_bps_limit(td, tg, bio, &bps_wait) | |
724 | && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) { | |
725 | if (wait) | |
726 | *wait = 0; | |
727 | return 1; | |
728 | } | |
729 | ||
730 | max_wait = max(bps_wait, iops_wait); | |
731 | ||
732 | if (wait) | |
733 | *wait = max_wait; | |
734 | ||
735 | if (time_before(tg->slice_end[rw], jiffies + max_wait)) | |
736 | throtl_extend_slice(td, tg, rw, jiffies + max_wait); | |
737 | ||
738 | return 0; | |
739 | } | |
740 | ||
741 | static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) | |
742 | { | |
743 | bool rw = bio_data_dir(bio); | |
744 | bool sync = rw_is_sync(bio->bi_rw); | |
745 | ||
746 | /* Charge the bio to the group */ | |
747 | tg->bytes_disp[rw] += bio->bi_size; | |
748 | tg->io_disp[rw]++; | |
749 | ||
750 | blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, rw, sync); | |
751 | } | |
752 | ||
753 | static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg, | |
754 | struct bio *bio) | |
755 | { | |
756 | bool rw = bio_data_dir(bio); | |
757 | ||
758 | bio_list_add(&tg->bio_lists[rw], bio); | |
759 | /* Take a bio reference on tg */ | |
760 | throtl_ref_get_tg(tg); | |
761 | tg->nr_queued[rw]++; | |
762 | td->nr_queued[rw]++; | |
763 | throtl_enqueue_tg(td, tg); | |
764 | } | |
765 | ||
766 | static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg) | |
767 | { | |
768 | unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; | |
769 | struct bio *bio; | |
770 | ||
771 | if ((bio = bio_list_peek(&tg->bio_lists[READ]))) | |
772 | tg_may_dispatch(td, tg, bio, &read_wait); | |
773 | ||
774 | if ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) | |
775 | tg_may_dispatch(td, tg, bio, &write_wait); | |
776 | ||
777 | min_wait = min(read_wait, write_wait); | |
778 | disptime = jiffies + min_wait; | |
779 | ||
780 | /* Update dispatch time */ | |
781 | throtl_dequeue_tg(td, tg); | |
782 | tg->disptime = disptime; | |
783 | throtl_enqueue_tg(td, tg); | |
784 | } | |
785 | ||
786 | static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg, | |
787 | bool rw, struct bio_list *bl) | |
788 | { | |
789 | struct bio *bio; | |
790 | ||
791 | bio = bio_list_pop(&tg->bio_lists[rw]); | |
792 | tg->nr_queued[rw]--; | |
793 | /* Drop bio reference on tg */ | |
794 | throtl_put_tg(tg); | |
795 | ||
796 | BUG_ON(td->nr_queued[rw] <= 0); | |
797 | td->nr_queued[rw]--; | |
798 | ||
799 | throtl_charge_bio(tg, bio); | |
800 | bio_list_add(bl, bio); | |
801 | bio->bi_rw |= REQ_THROTTLED; | |
802 | ||
803 | throtl_trim_slice(td, tg, rw); | |
804 | } | |
805 | ||
806 | static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, | |
807 | struct bio_list *bl) | |
808 | { | |
809 | unsigned int nr_reads = 0, nr_writes = 0; | |
810 | unsigned int max_nr_reads = throtl_grp_quantum*3/4; | |
811 | unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; | |
812 | struct bio *bio; | |
813 | ||
814 | /* Try to dispatch 75% READS and 25% WRITES */ | |
815 | ||
816 | while ((bio = bio_list_peek(&tg->bio_lists[READ])) | |
817 | && tg_may_dispatch(td, tg, bio, NULL)) { | |
818 | ||
819 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); | |
820 | nr_reads++; | |
821 | ||
822 | if (nr_reads >= max_nr_reads) | |
823 | break; | |
824 | } | |
825 | ||
826 | while ((bio = bio_list_peek(&tg->bio_lists[WRITE])) | |
827 | && tg_may_dispatch(td, tg, bio, NULL)) { | |
828 | ||
829 | tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); | |
830 | nr_writes++; | |
831 | ||
832 | if (nr_writes >= max_nr_writes) | |
833 | break; | |
834 | } | |
835 | ||
836 | return nr_reads + nr_writes; | |
837 | } | |
838 | ||
839 | static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) | |
840 | { | |
841 | unsigned int nr_disp = 0; | |
842 | struct throtl_grp *tg; | |
843 | struct throtl_rb_root *st = &td->tg_service_tree; | |
844 | ||
845 | while (1) { | |
846 | tg = throtl_rb_first(st); | |
847 | ||
848 | if (!tg) | |
849 | break; | |
850 | ||
851 | if (time_before(jiffies, tg->disptime)) | |
852 | break; | |
853 | ||
854 | throtl_dequeue_tg(td, tg); | |
855 | ||
856 | nr_disp += throtl_dispatch_tg(td, tg, bl); | |
857 | ||
858 | if (tg->nr_queued[0] || tg->nr_queued[1]) { | |
859 | tg_update_disptime(td, tg); | |
860 | throtl_enqueue_tg(td, tg); | |
861 | } | |
862 | ||
863 | if (nr_disp >= throtl_quantum) | |
864 | break; | |
865 | } | |
866 | ||
867 | return nr_disp; | |
868 | } | |
869 | ||
870 | static void throtl_process_limit_change(struct throtl_data *td) | |
871 | { | |
872 | struct throtl_grp *tg; | |
873 | struct hlist_node *pos, *n; | |
874 | ||
875 | if (!td->limits_changed) | |
876 | return; | |
877 | ||
878 | xchg(&td->limits_changed, false); | |
879 | ||
880 | throtl_log(td, "limits changed"); | |
881 | ||
882 | hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) { | |
883 | if (!tg->limits_changed) | |
884 | continue; | |
885 | ||
886 | if (!xchg(&tg->limits_changed, false)) | |
887 | continue; | |
888 | ||
889 | throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu" | |
890 | " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE], | |
891 | tg->iops[READ], tg->iops[WRITE]); | |
892 | ||
893 | /* | |
894 | * Restart the slices for both READ and WRITES. It | |
895 | * might happen that a group's limit are dropped | |
896 | * suddenly and we don't want to account recently | |
897 | * dispatched IO with new low rate | |
898 | */ | |
899 | throtl_start_new_slice(td, tg, 0); | |
900 | throtl_start_new_slice(td, tg, 1); | |
901 | ||
902 | if (throtl_tg_on_rr(tg)) | |
903 | tg_update_disptime(td, tg); | |
904 | } | |
905 | } | |
906 | ||
907 | /* Dispatch throttled bios. Should be called without queue lock held. */ | |
908 | static int throtl_dispatch(struct request_queue *q) | |
909 | { | |
910 | struct throtl_data *td = q->td; | |
911 | unsigned int nr_disp = 0; | |
912 | struct bio_list bio_list_on_stack; | |
913 | struct bio *bio; | |
914 | struct blk_plug plug; | |
915 | ||
916 | spin_lock_irq(q->queue_lock); | |
917 | ||
918 | throtl_process_limit_change(td); | |
919 | ||
920 | if (!total_nr_queued(td)) | |
921 | goto out; | |
922 | ||
923 | bio_list_init(&bio_list_on_stack); | |
924 | ||
925 | throtl_log(td, "dispatch nr_queued=%u read=%u write=%u", | |
926 | total_nr_queued(td), td->nr_queued[READ], | |
927 | td->nr_queued[WRITE]); | |
928 | ||
929 | nr_disp = throtl_select_dispatch(td, &bio_list_on_stack); | |
930 | ||
931 | if (nr_disp) | |
932 | throtl_log(td, "bios disp=%u", nr_disp); | |
933 | ||
934 | throtl_schedule_next_dispatch(td); | |
935 | out: | |
936 | spin_unlock_irq(q->queue_lock); | |
937 | ||
938 | /* | |
939 | * If we dispatched some requests, unplug the queue to make sure | |
940 | * immediate dispatch | |
941 | */ | |
942 | if (nr_disp) { | |
943 | blk_start_plug(&plug); | |
944 | while((bio = bio_list_pop(&bio_list_on_stack))) | |
945 | generic_make_request(bio); | |
946 | blk_finish_plug(&plug); | |
947 | } | |
948 | return nr_disp; | |
949 | } | |
950 | ||
951 | void blk_throtl_work(struct work_struct *work) | |
952 | { | |
953 | struct throtl_data *td = container_of(work, struct throtl_data, | |
954 | throtl_work.work); | |
955 | struct request_queue *q = td->queue; | |
956 | ||
957 | throtl_dispatch(q); | |
958 | } | |
959 | ||
960 | /* Call with queue lock held */ | |
961 | static void | |
962 | throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay) | |
963 | { | |
964 | ||
965 | struct delayed_work *dwork = &td->throtl_work; | |
966 | ||
967 | /* schedule work if limits changed even if no bio is queued */ | |
968 | if (total_nr_queued(td) || td->limits_changed) { | |
969 | /* | |
970 | * We might have a work scheduled to be executed in future. | |
971 | * Cancel that and schedule a new one. | |
972 | */ | |
973 | __cancel_delayed_work(dwork); | |
974 | queue_delayed_work(kthrotld_workqueue, dwork, delay); | |
975 | throtl_log(td, "schedule work. delay=%lu jiffies=%lu", | |
976 | delay, jiffies); | |
977 | } | |
978 | } | |
979 | ||
980 | static void | |
981 | throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg) | |
982 | { | |
983 | /* Something wrong if we are trying to remove same group twice */ | |
984 | BUG_ON(hlist_unhashed(&tg->tg_node)); | |
985 | ||
986 | hlist_del_init(&tg->tg_node); | |
987 | ||
988 | /* | |
989 | * Put the reference taken at the time of creation so that when all | |
990 | * queues are gone, group can be destroyed. | |
991 | */ | |
992 | throtl_put_tg(tg); | |
993 | td->nr_undestroyed_grps--; | |
994 | } | |
995 | ||
996 | static void throtl_release_tgs(struct throtl_data *td) | |
997 | { | |
998 | struct hlist_node *pos, *n; | |
999 | struct throtl_grp *tg; | |
1000 | ||
1001 | hlist_for_each_entry_safe(tg, pos, n, &td->tg_list, tg_node) { | |
1002 | /* | |
1003 | * If cgroup removal path got to blk_group first and removed | |
1004 | * it from cgroup list, then it will take care of destroying | |
1005 | * cfqg also. | |
1006 | */ | |
1007 | if (!blkiocg_del_blkio_group(&tg->blkg)) | |
1008 | throtl_destroy_tg(td, tg); | |
1009 | } | |
1010 | } | |
1011 | ||
1012 | static void throtl_td_free(struct throtl_data *td) | |
1013 | { | |
1014 | kfree(td); | |
1015 | } | |
1016 | ||
1017 | /* | |
1018 | * Blk cgroup controller notification saying that blkio_group object is being | |
1019 | * delinked as associated cgroup object is going away. That also means that | |
1020 | * no new IO will come in this group. So get rid of this group as soon as | |
1021 | * any pending IO in the group is finished. | |
1022 | * | |
1023 | * This function is called under rcu_read_lock(). key is the rcu protected | |
1024 | * pointer. That means "key" is a valid throtl_data pointer as long as we are | |
1025 | * rcu read lock. | |
1026 | * | |
1027 | * "key" was fetched from blkio_group under blkio_cgroup->lock. That means | |
1028 | * it should not be NULL as even if queue was going away, cgroup deltion | |
1029 | * path got to it first. | |
1030 | */ | |
1031 | void throtl_unlink_blkio_group(void *key, struct blkio_group *blkg) | |
1032 | { | |
1033 | unsigned long flags; | |
1034 | struct throtl_data *td = key; | |
1035 | ||
1036 | spin_lock_irqsave(td->queue->queue_lock, flags); | |
1037 | throtl_destroy_tg(td, tg_of_blkg(blkg)); | |
1038 | spin_unlock_irqrestore(td->queue->queue_lock, flags); | |
1039 | } | |
1040 | ||
1041 | static void throtl_update_blkio_group_common(struct throtl_data *td, | |
1042 | struct throtl_grp *tg) | |
1043 | { | |
1044 | xchg(&tg->limits_changed, true); | |
1045 | xchg(&td->limits_changed, true); | |
1046 | /* Schedule a work now to process the limit change */ | |
1047 | throtl_schedule_delayed_work(td, 0); | |
1048 | } | |
1049 | ||
1050 | /* | |
1051 | * For all update functions, key should be a valid pointer because these | |
1052 | * update functions are called under blkcg_lock, that means, blkg is | |
1053 | * valid and in turn key is valid. queue exit path can not race because | |
1054 | * of blkcg_lock | |
1055 | * | |
1056 | * Can not take queue lock in update functions as queue lock under blkcg_lock | |
1057 | * is not allowed. Under other paths we take blkcg_lock under queue_lock. | |
1058 | */ | |
1059 | static void throtl_update_blkio_group_read_bps(void *key, | |
1060 | struct blkio_group *blkg, u64 read_bps) | |
1061 | { | |
1062 | struct throtl_data *td = key; | |
1063 | struct throtl_grp *tg = tg_of_blkg(blkg); | |
1064 | ||
1065 | tg->bps[READ] = read_bps; | |
1066 | throtl_update_blkio_group_common(td, tg); | |
1067 | } | |
1068 | ||
1069 | static void throtl_update_blkio_group_write_bps(void *key, | |
1070 | struct blkio_group *blkg, u64 write_bps) | |
1071 | { | |
1072 | struct throtl_data *td = key; | |
1073 | struct throtl_grp *tg = tg_of_blkg(blkg); | |
1074 | ||
1075 | tg->bps[WRITE] = write_bps; | |
1076 | throtl_update_blkio_group_common(td, tg); | |
1077 | } | |
1078 | ||
1079 | static void throtl_update_blkio_group_read_iops(void *key, | |
1080 | struct blkio_group *blkg, unsigned int read_iops) | |
1081 | { | |
1082 | struct throtl_data *td = key; | |
1083 | struct throtl_grp *tg = tg_of_blkg(blkg); | |
1084 | ||
1085 | tg->iops[READ] = read_iops; | |
1086 | throtl_update_blkio_group_common(td, tg); | |
1087 | } | |
1088 | ||
1089 | static void throtl_update_blkio_group_write_iops(void *key, | |
1090 | struct blkio_group *blkg, unsigned int write_iops) | |
1091 | { | |
1092 | struct throtl_data *td = key; | |
1093 | struct throtl_grp *tg = tg_of_blkg(blkg); | |
1094 | ||
1095 | tg->iops[WRITE] = write_iops; | |
1096 | throtl_update_blkio_group_common(td, tg); | |
1097 | } | |
1098 | ||
1099 | static void throtl_shutdown_wq(struct request_queue *q) | |
1100 | { | |
1101 | struct throtl_data *td = q->td; | |
1102 | ||
1103 | cancel_delayed_work_sync(&td->throtl_work); | |
1104 | } | |
1105 | ||
1106 | static struct blkio_policy_type blkio_policy_throtl = { | |
1107 | .ops = { | |
1108 | .blkio_unlink_group_fn = throtl_unlink_blkio_group, | |
1109 | .blkio_update_group_read_bps_fn = | |
1110 | throtl_update_blkio_group_read_bps, | |
1111 | .blkio_update_group_write_bps_fn = | |
1112 | throtl_update_blkio_group_write_bps, | |
1113 | .blkio_update_group_read_iops_fn = | |
1114 | throtl_update_blkio_group_read_iops, | |
1115 | .blkio_update_group_write_iops_fn = | |
1116 | throtl_update_blkio_group_write_iops, | |
1117 | }, | |
1118 | .plid = BLKIO_POLICY_THROTL, | |
1119 | }; | |
1120 | ||
1121 | int blk_throtl_bio(struct request_queue *q, struct bio **biop) | |
1122 | { | |
1123 | struct throtl_data *td = q->td; | |
1124 | struct throtl_grp *tg; | |
1125 | struct bio *bio = *biop; | |
1126 | bool rw = bio_data_dir(bio), update_disptime = true; | |
1127 | struct blkio_cgroup *blkcg; | |
1128 | ||
1129 | if (bio->bi_rw & REQ_THROTTLED) { | |
1130 | bio->bi_rw &= ~REQ_THROTTLED; | |
1131 | return 0; | |
1132 | } | |
1133 | ||
1134 | /* | |
1135 | * A throtl_grp pointer retrieved under rcu can be used to access | |
1136 | * basic fields like stats and io rates. If a group has no rules, | |
1137 | * just update the dispatch stats in lockless manner and return. | |
1138 | */ | |
1139 | ||
1140 | rcu_read_lock(); | |
1141 | blkcg = task_blkio_cgroup(current); | |
1142 | tg = throtl_find_tg(td, blkcg); | |
1143 | if (tg) { | |
1144 | throtl_tg_fill_dev_details(td, tg); | |
1145 | ||
1146 | if (tg_no_rule_group(tg, rw)) { | |
1147 | blkiocg_update_dispatch_stats(&tg->blkg, bio->bi_size, | |
1148 | rw, rw_is_sync(bio->bi_rw)); | |
1149 | rcu_read_unlock(); | |
1150 | return 0; | |
1151 | } | |
1152 | } | |
1153 | rcu_read_unlock(); | |
1154 | ||
1155 | /* | |
1156 | * Either group has not been allocated yet or it is not an unlimited | |
1157 | * IO group | |
1158 | */ | |
1159 | ||
1160 | spin_lock_irq(q->queue_lock); | |
1161 | tg = throtl_get_tg(td); | |
1162 | ||
1163 | if (IS_ERR(tg)) { | |
1164 | if (PTR_ERR(tg) == -ENODEV) { | |
1165 | /* | |
1166 | * Queue is gone. No queue lock held here. | |
1167 | */ | |
1168 | return -ENODEV; | |
1169 | } | |
1170 | } | |
1171 | ||
1172 | if (tg->nr_queued[rw]) { | |
1173 | /* | |
1174 | * There is already another bio queued in same dir. No | |
1175 | * need to update dispatch time. | |
1176 | */ | |
1177 | update_disptime = false; | |
1178 | goto queue_bio; | |
1179 | ||
1180 | } | |
1181 | ||
1182 | /* Bio is with-in rate limit of group */ | |
1183 | if (tg_may_dispatch(td, tg, bio, NULL)) { | |
1184 | throtl_charge_bio(tg, bio); | |
1185 | ||
1186 | /* | |
1187 | * We need to trim slice even when bios are not being queued | |
1188 | * otherwise it might happen that a bio is not queued for | |
1189 | * a long time and slice keeps on extending and trim is not | |
1190 | * called for a long time. Now if limits are reduced suddenly | |
1191 | * we take into account all the IO dispatched so far at new | |
1192 | * low rate and * newly queued IO gets a really long dispatch | |
1193 | * time. | |
1194 | * | |
1195 | * So keep on trimming slice even if bio is not queued. | |
1196 | */ | |
1197 | throtl_trim_slice(td, tg, rw); | |
1198 | goto out; | |
1199 | } | |
1200 | ||
1201 | queue_bio: | |
1202 | throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu" | |
1203 | " iodisp=%u iops=%u queued=%d/%d", | |
1204 | rw == READ ? 'R' : 'W', | |
1205 | tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], | |
1206 | tg->io_disp[rw], tg->iops[rw], | |
1207 | tg->nr_queued[READ], tg->nr_queued[WRITE]); | |
1208 | ||
1209 | throtl_add_bio_tg(q->td, tg, bio); | |
1210 | *biop = NULL; | |
1211 | ||
1212 | if (update_disptime) { | |
1213 | tg_update_disptime(td, tg); | |
1214 | throtl_schedule_next_dispatch(td); | |
1215 | } | |
1216 | ||
1217 | out: | |
1218 | spin_unlock_irq(q->queue_lock); | |
1219 | return 0; | |
1220 | } | |
1221 | ||
1222 | int blk_throtl_init(struct request_queue *q) | |
1223 | { | |
1224 | struct throtl_data *td; | |
1225 | struct throtl_grp *tg; | |
1226 | ||
1227 | td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node); | |
1228 | if (!td) | |
1229 | return -ENOMEM; | |
1230 | ||
1231 | INIT_HLIST_HEAD(&td->tg_list); | |
1232 | td->tg_service_tree = THROTL_RB_ROOT; | |
1233 | td->limits_changed = false; | |
1234 | INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work); | |
1235 | ||
1236 | /* alloc and Init root group. */ | |
1237 | td->queue = q; | |
1238 | tg = throtl_alloc_tg(td); | |
1239 | ||
1240 | if (!tg) { | |
1241 | kfree(td); | |
1242 | return -ENOMEM; | |
1243 | } | |
1244 | ||
1245 | td->root_tg = tg; | |
1246 | ||
1247 | rcu_read_lock(); | |
1248 | throtl_init_add_tg_lists(td, tg, &blkio_root_cgroup); | |
1249 | rcu_read_unlock(); | |
1250 | ||
1251 | /* Attach throtl data to request queue */ | |
1252 | q->td = td; | |
1253 | return 0; | |
1254 | } | |
1255 | ||
1256 | void blk_throtl_exit(struct request_queue *q) | |
1257 | { | |
1258 | struct throtl_data *td = q->td; | |
1259 | bool wait = false; | |
1260 | ||
1261 | BUG_ON(!td); | |
1262 | ||
1263 | throtl_shutdown_wq(q); | |
1264 | ||
1265 | spin_lock_irq(q->queue_lock); | |
1266 | throtl_release_tgs(td); | |
1267 | ||
1268 | /* If there are other groups */ | |
1269 | if (td->nr_undestroyed_grps > 0) | |
1270 | wait = true; | |
1271 | ||
1272 | spin_unlock_irq(q->queue_lock); | |
1273 | ||
1274 | /* | |
1275 | * Wait for tg->blkg->key accessors to exit their grace periods. | |
1276 | * Do this wait only if there are other undestroyed groups out | |
1277 | * there (other than root group). This can happen if cgroup deletion | |
1278 | * path claimed the responsibility of cleaning up a group before | |
1279 | * queue cleanup code get to the group. | |
1280 | * | |
1281 | * Do not call synchronize_rcu() unconditionally as there are drivers | |
1282 | * which create/delete request queue hundreds of times during scan/boot | |
1283 | * and synchronize_rcu() can take significant time and slow down boot. | |
1284 | */ | |
1285 | if (wait) | |
1286 | synchronize_rcu(); | |
1287 | ||
1288 | /* | |
1289 | * Just being safe to make sure after previous flush if some body did | |
1290 | * update limits through cgroup and another work got queued, cancel | |
1291 | * it. | |
1292 | */ | |
1293 | throtl_shutdown_wq(q); | |
1294 | throtl_td_free(td); | |
1295 | } | |
1296 | ||
1297 | static int __init throtl_init(void) | |
1298 | { | |
1299 | kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0); | |
1300 | if (!kthrotld_workqueue) | |
1301 | panic("Failed to create kthrotld\n"); | |
1302 | ||
1303 | blkio_policy_register(&blkio_policy_throtl); | |
1304 | return 0; | |
1305 | } | |
1306 | ||
1307 | module_init(throtl_init); |