Commit | Line | Data |
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d7067512 JB |
1 | /* |
2 | * Block rq-qos base io controller | |
3 | * | |
4 | * This works similar to wbt with a few exceptions | |
5 | * | |
6 | * - It's bio based, so the latency covers the whole block layer in addition to | |
7 | * the actual io. | |
8 | * - We will throttle all IO that comes in here if we need to. | |
9 | * - We use the mean latency over the 100ms window. This is because writes can | |
10 | * be particularly fast, which could give us a false sense of the impact of | |
11 | * other workloads on our protected workload. | |
12 | * - By default there's no throttling, we set the queue_depth to INT_MAX so that | |
13 | * we can have as many outstanding bio's as we're allowed to. Only at | |
14 | * throttle time do we pay attention to the actual queue depth. | |
15 | * | |
16 | * The hierarchy works like the cpu controller does, we track the latency at | |
17 | * every configured node, and each configured node has it's own independent | |
18 | * queue depth. This means that we only care about our latency targets at the | |
19 | * peer level. Some group at the bottom of the hierarchy isn't going to affect | |
20 | * a group at the end of some other path if we're only configred at leaf level. | |
21 | * | |
22 | * Consider the following | |
23 | * | |
24 | * root blkg | |
25 | * / \ | |
26 | * fast (target=5ms) slow (target=10ms) | |
27 | * / \ / \ | |
28 | * a b normal(15ms) unloved | |
29 | * | |
30 | * "a" and "b" have no target, but their combined io under "fast" cannot exceed | |
31 | * an average latency of 5ms. If it does then we will throttle the "slow" | |
32 | * group. In the case of "normal", if it exceeds its 15ms target, we will | |
33 | * throttle "unloved", but nobody else. | |
34 | * | |
35 | * In this example "fast", "slow", and "normal" will be the only groups actually | |
36 | * accounting their io latencies. We have to walk up the heirarchy to the root | |
37 | * on every submit and complete so we can do the appropriate stat recording and | |
38 | * adjust the queue depth of ourselves if needed. | |
39 | * | |
40 | * There are 2 ways we throttle IO. | |
41 | * | |
42 | * 1) Queue depth throttling. As we throttle down we will adjust the maximum | |
43 | * number of IO's we're allowed to have in flight. This starts at (u64)-1 down | |
44 | * to 1. If the group is only ever submitting IO for itself then this is the | |
45 | * only way we throttle. | |
46 | * | |
47 | * 2) Induced delay throttling. This is for the case that a group is generating | |
48 | * IO that has to be issued by the root cg to avoid priority inversion. So think | |
49 | * REQ_META or REQ_SWAP. If we are already at qd == 1 and we're getting a lot | |
50 | * of work done for us on behalf of the root cg and are being asked to scale | |
51 | * down more then we induce a latency at userspace return. We accumulate the | |
52 | * total amount of time we need to be punished by doing | |
53 | * | |
54 | * total_time += min_lat_nsec - actual_io_completion | |
55 | * | |
56 | * and then at throttle time will do | |
57 | * | |
58 | * throttle_time = min(total_time, NSEC_PER_SEC) | |
59 | * | |
60 | * This induced delay will throttle back the activity that is generating the | |
61 | * root cg issued io's, wethere that's some metadata intensive operation or the | |
62 | * group is using so much memory that it is pushing us into swap. | |
63 | * | |
64 | * Copyright (C) 2018 Josef Bacik | |
65 | */ | |
66 | #include <linux/kernel.h> | |
67 | #include <linux/blk_types.h> | |
68 | #include <linux/backing-dev.h> | |
69 | #include <linux/module.h> | |
70 | #include <linux/timer.h> | |
71 | #include <linux/memcontrol.h> | |
72 | #include <linux/sched/signal.h> | |
73 | #include <trace/events/block.h> | |
74 | #include "blk-rq-qos.h" | |
75 | #include "blk-stat.h" | |
76 | ||
77 | #define DEFAULT_SCALE_COOKIE 1000000U | |
78 | ||
79 | static struct blkcg_policy blkcg_policy_iolatency; | |
80 | struct iolatency_grp; | |
81 | ||
82 | struct blk_iolatency { | |
83 | struct rq_qos rqos; | |
84 | struct timer_list timer; | |
85 | atomic_t enabled; | |
86 | }; | |
87 | ||
88 | static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) | |
89 | { | |
90 | return container_of(rqos, struct blk_iolatency, rqos); | |
91 | } | |
92 | ||
93 | static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat) | |
94 | { | |
95 | return atomic_read(&blkiolat->enabled) > 0; | |
96 | } | |
97 | ||
98 | struct child_latency_info { | |
99 | spinlock_t lock; | |
100 | ||
101 | /* Last time we adjusted the scale of everybody. */ | |
102 | u64 last_scale_event; | |
103 | ||
104 | /* The latency that we missed. */ | |
105 | u64 scale_lat; | |
106 | ||
107 | /* Total io's from all of our children for the last summation. */ | |
108 | u64 nr_samples; | |
109 | ||
110 | /* The guy who actually changed the latency numbers. */ | |
111 | struct iolatency_grp *scale_grp; | |
112 | ||
113 | /* Cookie to tell if we need to scale up or down. */ | |
114 | atomic_t scale_cookie; | |
115 | }; | |
116 | ||
117 | struct iolatency_grp { | |
118 | struct blkg_policy_data pd; | |
119 | struct blk_rq_stat __percpu *stats; | |
120 | struct blk_iolatency *blkiolat; | |
121 | struct rq_depth rq_depth; | |
122 | struct rq_wait rq_wait; | |
123 | atomic64_t window_start; | |
124 | atomic_t scale_cookie; | |
125 | u64 min_lat_nsec; | |
126 | u64 cur_win_nsec; | |
127 | ||
128 | /* total running average of our io latency. */ | |
129 | u64 total_lat_avg; | |
130 | u64 total_lat_nr; | |
131 | ||
132 | /* Our current number of IO's for the last summation. */ | |
133 | u64 nr_samples; | |
134 | ||
135 | struct child_latency_info child_lat; | |
136 | }; | |
137 | ||
138 | static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd) | |
139 | { | |
140 | return pd ? container_of(pd, struct iolatency_grp, pd) : NULL; | |
141 | } | |
142 | ||
143 | static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg) | |
144 | { | |
145 | return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency)); | |
146 | } | |
147 | ||
148 | static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat) | |
149 | { | |
150 | return pd_to_blkg(&iolat->pd); | |
151 | } | |
152 | ||
153 | static inline bool iolatency_may_queue(struct iolatency_grp *iolat, | |
154 | wait_queue_entry_t *wait, | |
155 | bool first_block) | |
156 | { | |
157 | struct rq_wait *rqw = &iolat->rq_wait; | |
158 | ||
159 | if (first_block && waitqueue_active(&rqw->wait) && | |
160 | rqw->wait.head.next != &wait->entry) | |
161 | return false; | |
162 | return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth); | |
163 | } | |
164 | ||
165 | static void __blkcg_iolatency_throttle(struct rq_qos *rqos, | |
166 | struct iolatency_grp *iolat, | |
167 | spinlock_t *lock, bool issue_as_root, | |
168 | bool use_memdelay) | |
169 | __releases(lock) | |
170 | __acquires(lock) | |
171 | { | |
172 | struct rq_wait *rqw = &iolat->rq_wait; | |
173 | unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay); | |
174 | DEFINE_WAIT(wait); | |
175 | bool first_block = true; | |
176 | ||
177 | if (use_delay) | |
178 | blkcg_schedule_throttle(rqos->q, use_memdelay); | |
179 | ||
180 | /* | |
181 | * To avoid priority inversions we want to just take a slot if we are | |
182 | * issuing as root. If we're being killed off there's no point in | |
183 | * delaying things, we may have been killed by OOM so throttling may | |
184 | * make recovery take even longer, so just let the IO's through so the | |
185 | * task can go away. | |
186 | */ | |
187 | if (issue_as_root || fatal_signal_pending(current)) { | |
188 | atomic_inc(&rqw->inflight); | |
189 | return; | |
190 | } | |
191 | ||
192 | if (iolatency_may_queue(iolat, &wait, first_block)) | |
193 | return; | |
194 | ||
195 | do { | |
196 | prepare_to_wait_exclusive(&rqw->wait, &wait, | |
197 | TASK_UNINTERRUPTIBLE); | |
198 | ||
199 | if (iolatency_may_queue(iolat, &wait, first_block)) | |
200 | break; | |
201 | first_block = false; | |
202 | ||
203 | if (lock) { | |
204 | spin_unlock_irq(lock); | |
205 | io_schedule(); | |
206 | spin_lock_irq(lock); | |
207 | } else { | |
208 | io_schedule(); | |
209 | } | |
210 | } while (1); | |
211 | ||
212 | finish_wait(&rqw->wait, &wait); | |
213 | } | |
214 | ||
215 | #define SCALE_DOWN_FACTOR 2 | |
216 | #define SCALE_UP_FACTOR 4 | |
217 | ||
218 | static inline unsigned long scale_amount(unsigned long qd, bool up) | |
219 | { | |
220 | return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL); | |
221 | } | |
222 | ||
223 | /* | |
224 | * We scale the qd down faster than we scale up, so we need to use this helper | |
225 | * to adjust the scale_cookie accordingly so we don't prematurely get | |
226 | * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much. | |
227 | * | |
228 | * Each group has their own local copy of the last scale cookie they saw, so if | |
229 | * the global scale cookie goes up or down they know which way they need to go | |
230 | * based on their last knowledge of it. | |
231 | */ | |
232 | static void scale_cookie_change(struct blk_iolatency *blkiolat, | |
233 | struct child_latency_info *lat_info, | |
234 | bool up) | |
235 | { | |
236 | unsigned long qd = blk_queue_depth(blkiolat->rqos.q); | |
237 | unsigned long scale = scale_amount(qd, up); | |
238 | unsigned long old = atomic_read(&lat_info->scale_cookie); | |
239 | unsigned long max_scale = qd << 1; | |
240 | unsigned long diff = 0; | |
241 | ||
242 | if (old < DEFAULT_SCALE_COOKIE) | |
243 | diff = DEFAULT_SCALE_COOKIE - old; | |
244 | ||
245 | if (up) { | |
246 | if (scale + old > DEFAULT_SCALE_COOKIE) | |
247 | atomic_set(&lat_info->scale_cookie, | |
248 | DEFAULT_SCALE_COOKIE); | |
249 | else if (diff > qd) | |
250 | atomic_inc(&lat_info->scale_cookie); | |
251 | else | |
252 | atomic_add(scale, &lat_info->scale_cookie); | |
253 | } else { | |
254 | /* | |
255 | * We don't want to dig a hole so deep that it takes us hours to | |
256 | * dig out of it. Just enough that we don't throttle/unthrottle | |
257 | * with jagged workloads but can still unthrottle once pressure | |
258 | * has sufficiently dissipated. | |
259 | */ | |
260 | if (diff > qd) { | |
261 | if (diff < max_scale) | |
262 | atomic_dec(&lat_info->scale_cookie); | |
263 | } else { | |
264 | atomic_sub(scale, &lat_info->scale_cookie); | |
265 | } | |
266 | } | |
267 | } | |
268 | ||
269 | /* | |
270 | * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the | |
271 | * queue depth at a time so we don't get wild swings and hopefully dial in to | |
272 | * fairer distribution of the overall queue depth. | |
273 | */ | |
274 | static void scale_change(struct iolatency_grp *iolat, bool up) | |
275 | { | |
276 | unsigned long qd = blk_queue_depth(iolat->blkiolat->rqos.q); | |
277 | unsigned long scale = scale_amount(qd, up); | |
278 | unsigned long old = iolat->rq_depth.max_depth; | |
279 | bool changed = false; | |
280 | ||
281 | if (old > qd) | |
282 | old = qd; | |
283 | ||
284 | if (up) { | |
285 | if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat))) | |
286 | return; | |
287 | ||
288 | if (old < qd) { | |
289 | changed = true; | |
290 | old += scale; | |
291 | old = min(old, qd); | |
292 | iolat->rq_depth.max_depth = old; | |
293 | wake_up_all(&iolat->rq_wait.wait); | |
294 | } | |
295 | } else if (old > 1) { | |
296 | old >>= 1; | |
297 | changed = true; | |
298 | iolat->rq_depth.max_depth = max(old, 1UL); | |
299 | } | |
300 | } | |
301 | ||
302 | /* Check our parent and see if the scale cookie has changed. */ | |
303 | static void check_scale_change(struct iolatency_grp *iolat) | |
304 | { | |
305 | struct iolatency_grp *parent; | |
306 | struct child_latency_info *lat_info; | |
307 | unsigned int cur_cookie; | |
308 | unsigned int our_cookie = atomic_read(&iolat->scale_cookie); | |
309 | u64 scale_lat; | |
310 | unsigned int old; | |
311 | int direction = 0; | |
312 | ||
313 | if (lat_to_blkg(iolat)->parent == NULL) | |
314 | return; | |
315 | ||
316 | parent = blkg_to_lat(lat_to_blkg(iolat)->parent); | |
317 | if (!parent) | |
318 | return; | |
319 | ||
320 | lat_info = &parent->child_lat; | |
321 | cur_cookie = atomic_read(&lat_info->scale_cookie); | |
322 | scale_lat = READ_ONCE(lat_info->scale_lat); | |
323 | ||
324 | if (cur_cookie < our_cookie) | |
325 | direction = -1; | |
326 | else if (cur_cookie > our_cookie) | |
327 | direction = 1; | |
328 | else | |
329 | return; | |
330 | ||
331 | old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie); | |
332 | ||
333 | /* Somebody beat us to the punch, just bail. */ | |
334 | if (old != our_cookie) | |
335 | return; | |
336 | ||
337 | if (direction < 0 && iolat->min_lat_nsec) { | |
338 | u64 samples_thresh; | |
339 | ||
340 | if (!scale_lat || iolat->min_lat_nsec <= scale_lat) | |
341 | return; | |
342 | ||
343 | /* | |
344 | * Sometimes high priority groups are their own worst enemy, so | |
345 | * instead of taking it out on some poor other group that did 5% | |
346 | * or less of the IO's for the last summation just skip this | |
347 | * scale down event. | |
348 | */ | |
349 | samples_thresh = lat_info->nr_samples * 5; | |
350 | samples_thresh = div64_u64(samples_thresh, 100); | |
351 | if (iolat->nr_samples <= samples_thresh) | |
352 | return; | |
353 | } | |
354 | ||
355 | /* We're as low as we can go. */ | |
356 | if (iolat->rq_depth.max_depth == 1 && direction < 0) { | |
357 | blkcg_use_delay(lat_to_blkg(iolat)); | |
358 | return; | |
359 | } | |
360 | ||
361 | /* We're back to the default cookie, unthrottle all the things. */ | |
362 | if (cur_cookie == DEFAULT_SCALE_COOKIE) { | |
363 | blkcg_clear_delay(lat_to_blkg(iolat)); | |
364 | iolat->rq_depth.max_depth = INT_MAX; | |
365 | wake_up_all(&iolat->rq_wait.wait); | |
366 | return; | |
367 | } | |
368 | ||
369 | scale_change(iolat, direction > 0); | |
370 | } | |
371 | ||
372 | static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio, | |
373 | spinlock_t *lock) | |
374 | { | |
375 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
376 | struct blkcg *blkcg; | |
377 | struct blkcg_gq *blkg; | |
378 | struct request_queue *q = rqos->q; | |
379 | bool issue_as_root = bio_issue_as_root_blkg(bio); | |
380 | ||
381 | if (!blk_iolatency_enabled(blkiolat)) | |
382 | return; | |
383 | ||
384 | rcu_read_lock(); | |
385 | blkcg = bio_blkcg(bio); | |
386 | bio_associate_blkcg(bio, &blkcg->css); | |
387 | blkg = blkg_lookup(blkcg, q); | |
388 | if (unlikely(!blkg)) { | |
389 | if (!lock) | |
390 | spin_lock_irq(q->queue_lock); | |
391 | blkg = blkg_lookup_create(blkcg, q); | |
392 | if (IS_ERR(blkg)) | |
393 | blkg = NULL; | |
394 | if (!lock) | |
395 | spin_unlock_irq(q->queue_lock); | |
396 | } | |
397 | if (!blkg) | |
398 | goto out; | |
399 | ||
400 | bio_issue_init(&bio->bi_issue, bio_sectors(bio)); | |
401 | bio_associate_blkg(bio, blkg); | |
402 | out: | |
403 | rcu_read_unlock(); | |
404 | while (blkg && blkg->parent) { | |
405 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
406 | if (!iolat) { | |
407 | blkg = blkg->parent; | |
408 | continue; | |
409 | } | |
410 | ||
411 | check_scale_change(iolat); | |
412 | __blkcg_iolatency_throttle(rqos, iolat, lock, issue_as_root, | |
413 | (bio->bi_opf & REQ_SWAP) == REQ_SWAP); | |
414 | blkg = blkg->parent; | |
415 | } | |
416 | if (!timer_pending(&blkiolat->timer)) | |
417 | mod_timer(&blkiolat->timer, jiffies + HZ); | |
418 | } | |
419 | ||
420 | static void iolatency_record_time(struct iolatency_grp *iolat, | |
421 | struct bio_issue *issue, u64 now, | |
422 | bool issue_as_root) | |
423 | { | |
424 | struct blk_rq_stat *rq_stat; | |
425 | u64 start = bio_issue_time(issue); | |
426 | u64 req_time; | |
427 | ||
428 | if (now <= start) | |
429 | return; | |
430 | ||
431 | req_time = now - start; | |
432 | ||
433 | /* | |
434 | * We don't want to count issue_as_root bio's in the cgroups latency | |
435 | * statistics as it could skew the numbers downwards. | |
436 | */ | |
437 | if (unlikely(issue_as_root && iolat->rq_depth.max_depth != (u64)-1)) { | |
438 | u64 sub = iolat->min_lat_nsec; | |
439 | if (req_time < sub) | |
440 | blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time); | |
441 | return; | |
442 | } | |
443 | ||
444 | rq_stat = get_cpu_ptr(iolat->stats); | |
445 | blk_rq_stat_add(rq_stat, req_time); | |
446 | put_cpu_ptr(rq_stat); | |
447 | } | |
448 | ||
449 | #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC) | |
450 | #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5 | |
451 | ||
452 | static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) | |
453 | { | |
454 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
455 | struct iolatency_grp *parent; | |
456 | struct child_latency_info *lat_info; | |
457 | struct blk_rq_stat stat; | |
458 | unsigned long flags; | |
459 | int cpu; | |
460 | ||
461 | blk_rq_stat_init(&stat); | |
462 | preempt_disable(); | |
463 | for_each_online_cpu(cpu) { | |
464 | struct blk_rq_stat *s; | |
465 | s = per_cpu_ptr(iolat->stats, cpu); | |
466 | blk_rq_stat_sum(&stat, s); | |
467 | blk_rq_stat_init(s); | |
468 | } | |
469 | preempt_enable(); | |
470 | ||
471 | /* | |
472 | * Our average exceeded our window, scale up our window so we are more | |
473 | * accurate, but not more than the global timer. | |
474 | */ | |
475 | if (stat.mean > iolat->cur_win_nsec) { | |
476 | iolat->cur_win_nsec <<= 1; | |
477 | iolat->cur_win_nsec = | |
478 | max_t(u64, iolat->cur_win_nsec, NSEC_PER_SEC); | |
479 | } | |
480 | ||
481 | parent = blkg_to_lat(blkg->parent); | |
482 | if (!parent) | |
483 | return; | |
484 | ||
485 | lat_info = &parent->child_lat; | |
486 | ||
487 | iolat->total_lat_avg = | |
488 | div64_u64((iolat->total_lat_avg * iolat->total_lat_nr) + | |
489 | stat.mean, iolat->total_lat_nr + 1); | |
490 | ||
491 | iolat->total_lat_nr++; | |
492 | ||
493 | /* Everything is ok and we don't need to adjust the scale. */ | |
494 | if (stat.mean <= iolat->min_lat_nsec && | |
495 | atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE) | |
496 | return; | |
497 | ||
498 | /* Somebody beat us to the punch, just bail. */ | |
499 | spin_lock_irqsave(&lat_info->lock, flags); | |
500 | lat_info->nr_samples -= iolat->nr_samples; | |
501 | lat_info->nr_samples += stat.nr_samples; | |
502 | iolat->nr_samples = stat.nr_samples; | |
503 | ||
504 | if ((lat_info->last_scale_event >= now || | |
505 | now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME) && | |
506 | lat_info->scale_lat <= iolat->min_lat_nsec) | |
507 | goto out; | |
508 | ||
509 | if (stat.mean <= iolat->min_lat_nsec && | |
510 | stat.nr_samples >= BLKIOLATENCY_MIN_GOOD_SAMPLES) { | |
511 | if (lat_info->scale_grp == iolat) { | |
512 | lat_info->last_scale_event = now; | |
513 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
514 | } | |
515 | } else if (stat.mean > iolat->min_lat_nsec) { | |
516 | lat_info->last_scale_event = now; | |
517 | if (!lat_info->scale_grp || | |
518 | lat_info->scale_lat > iolat->min_lat_nsec) { | |
519 | WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec); | |
520 | lat_info->scale_grp = iolat; | |
521 | } | |
522 | scale_cookie_change(iolat->blkiolat, lat_info, false); | |
523 | } | |
524 | out: | |
525 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
526 | } | |
527 | ||
528 | static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio) | |
529 | { | |
530 | struct blkcg_gq *blkg; | |
531 | struct rq_wait *rqw; | |
532 | struct iolatency_grp *iolat; | |
533 | u64 window_start; | |
534 | u64 now = ktime_to_ns(ktime_get()); | |
535 | bool issue_as_root = bio_issue_as_root_blkg(bio); | |
536 | bool enabled = false; | |
537 | ||
538 | blkg = bio->bi_blkg; | |
539 | if (!blkg) | |
540 | return; | |
541 | ||
542 | iolat = blkg_to_lat(bio->bi_blkg); | |
543 | if (!iolat) | |
544 | return; | |
545 | ||
546 | enabled = blk_iolatency_enabled(iolat->blkiolat); | |
547 | while (blkg && blkg->parent) { | |
548 | iolat = blkg_to_lat(blkg); | |
549 | if (!iolat) { | |
550 | blkg = blkg->parent; | |
551 | continue; | |
552 | } | |
553 | rqw = &iolat->rq_wait; | |
554 | ||
555 | atomic_dec(&rqw->inflight); | |
556 | if (!enabled || iolat->min_lat_nsec == 0) | |
557 | goto next; | |
558 | iolatency_record_time(iolat, &bio->bi_issue, now, | |
559 | issue_as_root); | |
560 | window_start = atomic64_read(&iolat->window_start); | |
561 | if (now > window_start && | |
562 | (now - window_start) >= iolat->cur_win_nsec) { | |
563 | if (atomic64_cmpxchg(&iolat->window_start, | |
564 | window_start, now) == window_start) | |
565 | iolatency_check_latencies(iolat, now); | |
566 | } | |
567 | next: | |
568 | wake_up(&rqw->wait); | |
569 | blkg = blkg->parent; | |
570 | } | |
571 | } | |
572 | ||
573 | static void blkcg_iolatency_cleanup(struct rq_qos *rqos, struct bio *bio) | |
574 | { | |
575 | struct blkcg_gq *blkg; | |
576 | ||
577 | blkg = bio->bi_blkg; | |
578 | while (blkg && blkg->parent) { | |
579 | struct rq_wait *rqw; | |
580 | struct iolatency_grp *iolat; | |
581 | ||
582 | iolat = blkg_to_lat(blkg); | |
583 | if (!iolat) | |
584 | goto next; | |
585 | ||
586 | rqw = &iolat->rq_wait; | |
587 | atomic_dec(&rqw->inflight); | |
588 | wake_up(&rqw->wait); | |
589 | next: | |
590 | blkg = blkg->parent; | |
591 | } | |
592 | } | |
593 | ||
594 | static void blkcg_iolatency_exit(struct rq_qos *rqos) | |
595 | { | |
596 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
597 | ||
598 | del_timer_sync(&blkiolat->timer); | |
599 | blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency); | |
600 | kfree(blkiolat); | |
601 | } | |
602 | ||
603 | static struct rq_qos_ops blkcg_iolatency_ops = { | |
604 | .throttle = blkcg_iolatency_throttle, | |
605 | .cleanup = blkcg_iolatency_cleanup, | |
606 | .done_bio = blkcg_iolatency_done_bio, | |
607 | .exit = blkcg_iolatency_exit, | |
608 | }; | |
609 | ||
610 | static void blkiolatency_timer_fn(struct timer_list *t) | |
611 | { | |
612 | struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer); | |
613 | struct blkcg_gq *blkg; | |
614 | struct cgroup_subsys_state *pos_css; | |
615 | u64 now = ktime_to_ns(ktime_get()); | |
616 | ||
617 | rcu_read_lock(); | |
618 | blkg_for_each_descendant_pre(blkg, pos_css, | |
619 | blkiolat->rqos.q->root_blkg) { | |
620 | struct iolatency_grp *iolat; | |
621 | struct child_latency_info *lat_info; | |
622 | unsigned long flags; | |
623 | u64 cookie; | |
624 | ||
625 | /* | |
626 | * We could be exiting, don't access the pd unless we have a | |
627 | * ref on the blkg. | |
628 | */ | |
629 | if (!blkg_try_get(blkg)) | |
630 | continue; | |
631 | ||
632 | iolat = blkg_to_lat(blkg); | |
633 | if (!iolat) | |
634 | continue; | |
635 | ||
636 | lat_info = &iolat->child_lat; | |
637 | cookie = atomic_read(&lat_info->scale_cookie); | |
638 | ||
639 | if (cookie >= DEFAULT_SCALE_COOKIE) | |
640 | goto next; | |
641 | ||
642 | spin_lock_irqsave(&lat_info->lock, flags); | |
643 | if (lat_info->last_scale_event >= now) | |
644 | goto next_lock; | |
645 | ||
646 | /* | |
647 | * We scaled down but don't have a scale_grp, scale up and carry | |
648 | * on. | |
649 | */ | |
650 | if (lat_info->scale_grp == NULL) { | |
651 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
652 | goto next_lock; | |
653 | } | |
654 | ||
655 | /* | |
656 | * It's been 5 seconds since our last scale event, clear the | |
657 | * scale grp in case the group that needed the scale down isn't | |
658 | * doing any IO currently. | |
659 | */ | |
660 | if (now - lat_info->last_scale_event >= | |
661 | ((u64)NSEC_PER_SEC * 5)) | |
662 | lat_info->scale_grp = NULL; | |
663 | next_lock: | |
664 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
665 | next: | |
666 | blkg_put(blkg); | |
667 | } | |
668 | rcu_read_unlock(); | |
669 | } | |
670 | ||
671 | int blk_iolatency_init(struct request_queue *q) | |
672 | { | |
673 | struct blk_iolatency *blkiolat; | |
674 | struct rq_qos *rqos; | |
675 | int ret; | |
676 | ||
677 | blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL); | |
678 | if (!blkiolat) | |
679 | return -ENOMEM; | |
680 | ||
681 | rqos = &blkiolat->rqos; | |
682 | rqos->id = RQ_QOS_CGROUP; | |
683 | rqos->ops = &blkcg_iolatency_ops; | |
684 | rqos->q = q; | |
685 | ||
686 | rq_qos_add(q, rqos); | |
687 | ||
688 | ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); | |
689 | if (ret) { | |
690 | rq_qos_del(q, rqos); | |
691 | kfree(blkiolat); | |
692 | return ret; | |
693 | } | |
694 | ||
695 | timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); | |
696 | ||
697 | return 0; | |
698 | } | |
699 | ||
700 | static void iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) | |
701 | { | |
702 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
703 | struct blk_iolatency *blkiolat = iolat->blkiolat; | |
704 | u64 oldval = iolat->min_lat_nsec; | |
705 | ||
706 | iolat->min_lat_nsec = val; | |
707 | iolat->cur_win_nsec = max_t(u64, val << 4, 100 * NSEC_PER_MSEC); | |
708 | iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, NSEC_PER_SEC); | |
709 | ||
710 | if (!oldval && val) | |
711 | atomic_inc(&blkiolat->enabled); | |
712 | if (oldval && !val) | |
713 | atomic_dec(&blkiolat->enabled); | |
714 | } | |
715 | ||
716 | static void iolatency_clear_scaling(struct blkcg_gq *blkg) | |
717 | { | |
718 | if (blkg->parent) { | |
719 | struct iolatency_grp *iolat = blkg_to_lat(blkg->parent); | |
720 | struct child_latency_info *lat_info; | |
721 | if (!iolat) | |
722 | return; | |
723 | ||
724 | lat_info = &iolat->child_lat; | |
725 | spin_lock(&lat_info->lock); | |
726 | atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE); | |
727 | lat_info->last_scale_event = 0; | |
728 | lat_info->scale_grp = NULL; | |
729 | lat_info->scale_lat = 0; | |
730 | spin_unlock(&lat_info->lock); | |
731 | } | |
732 | } | |
733 | ||
734 | static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, | |
735 | size_t nbytes, loff_t off) | |
736 | { | |
737 | struct blkcg *blkcg = css_to_blkcg(of_css(of)); | |
738 | struct blkcg_gq *blkg; | |
739 | struct blk_iolatency *blkiolat; | |
740 | struct blkg_conf_ctx ctx; | |
741 | struct iolatency_grp *iolat; | |
742 | char *p, *tok; | |
743 | u64 lat_val = 0; | |
744 | u64 oldval; | |
745 | int ret; | |
746 | ||
747 | ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); | |
748 | if (ret) | |
749 | return ret; | |
750 | ||
751 | iolat = blkg_to_lat(ctx.blkg); | |
752 | blkiolat = iolat->blkiolat; | |
753 | p = ctx.body; | |
754 | ||
755 | ret = -EINVAL; | |
756 | while ((tok = strsep(&p, " "))) { | |
757 | char key[16]; | |
758 | char val[21]; /* 18446744073709551616 */ | |
759 | ||
760 | if (sscanf(tok, "%15[^=]=%20s", key, val) != 2) | |
761 | goto out; | |
762 | ||
763 | if (!strcmp(key, "target")) { | |
764 | u64 v; | |
765 | ||
766 | if (!strcmp(val, "max")) | |
767 | lat_val = 0; | |
768 | else if (sscanf(val, "%llu", &v) == 1) | |
769 | lat_val = v * NSEC_PER_USEC; | |
770 | else | |
771 | goto out; | |
772 | } else { | |
773 | goto out; | |
774 | } | |
775 | } | |
776 | ||
777 | /* Walk up the tree to see if our new val is lower than it should be. */ | |
778 | blkg = ctx.blkg; | |
779 | oldval = iolat->min_lat_nsec; | |
780 | ||
781 | iolatency_set_min_lat_nsec(blkg, lat_val); | |
782 | if (oldval != iolat->min_lat_nsec) { | |
783 | iolatency_clear_scaling(blkg); | |
784 | } | |
785 | ||
786 | ret = 0; | |
787 | out: | |
788 | blkg_conf_finish(&ctx); | |
789 | return ret ?: nbytes; | |
790 | } | |
791 | ||
792 | static u64 iolatency_prfill_limit(struct seq_file *sf, | |
793 | struct blkg_policy_data *pd, int off) | |
794 | { | |
795 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
796 | const char *dname = blkg_dev_name(pd->blkg); | |
797 | ||
798 | if (!dname || !iolat->min_lat_nsec) | |
799 | return 0; | |
800 | seq_printf(sf, "%s target=%llu\n", | |
801 | dname, | |
802 | (unsigned long long)iolat->min_lat_nsec / NSEC_PER_USEC); | |
803 | return 0; | |
804 | } | |
805 | ||
806 | static int iolatency_print_limit(struct seq_file *sf, void *v) | |
807 | { | |
808 | blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), | |
809 | iolatency_prfill_limit, | |
810 | &blkcg_policy_iolatency, seq_cft(sf)->private, false); | |
811 | return 0; | |
812 | } | |
813 | ||
814 | static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf, | |
815 | size_t size) | |
816 | { | |
817 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
818 | unsigned long long avg_lat = div64_u64(iolat->total_lat_avg, NSEC_PER_USEC); | |
819 | ||
820 | if (iolat->rq_depth.max_depth == (u64)-1) | |
821 | return scnprintf(buf, size, " depth=max avg_lat=%llu", | |
822 | avg_lat); | |
823 | ||
824 | return scnprintf(buf, size, " depth=%u avg_lat=%llu", | |
825 | iolat->rq_depth.max_depth, avg_lat); | |
826 | } | |
827 | ||
828 | ||
829 | static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, int node) | |
830 | { | |
831 | struct iolatency_grp *iolat; | |
832 | ||
833 | iolat = kzalloc_node(sizeof(*iolat), gfp, node); | |
834 | if (!iolat) | |
835 | return NULL; | |
836 | iolat->stats = __alloc_percpu_gfp(sizeof(struct blk_rq_stat), | |
837 | __alignof__(struct blk_rq_stat), gfp); | |
838 | if (!iolat->stats) { | |
839 | kfree(iolat); | |
840 | return NULL; | |
841 | } | |
842 | return &iolat->pd; | |
843 | } | |
844 | ||
845 | static void iolatency_pd_init(struct blkg_policy_data *pd) | |
846 | { | |
847 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
848 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
849 | struct rq_qos *rqos = blkcg_rq_qos(blkg->q); | |
850 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
851 | u64 now = ktime_to_ns(ktime_get()); | |
852 | int cpu; | |
853 | ||
854 | for_each_possible_cpu(cpu) { | |
855 | struct blk_rq_stat *stat; | |
856 | stat = per_cpu_ptr(iolat->stats, cpu); | |
857 | blk_rq_stat_init(stat); | |
858 | } | |
859 | ||
860 | rq_wait_init(&iolat->rq_wait); | |
861 | spin_lock_init(&iolat->child_lat.lock); | |
862 | iolat->rq_depth.queue_depth = blk_queue_depth(blkg->q); | |
863 | iolat->rq_depth.max_depth = INT_MAX; | |
864 | iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth; | |
865 | iolat->blkiolat = blkiolat; | |
866 | iolat->cur_win_nsec = 100 * NSEC_PER_MSEC; | |
867 | atomic64_set(&iolat->window_start, now); | |
868 | ||
869 | /* | |
870 | * We init things in list order, so the pd for the parent may not be | |
871 | * init'ed yet for whatever reason. | |
872 | */ | |
873 | if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) { | |
874 | struct iolatency_grp *parent = blkg_to_lat(blkg->parent); | |
875 | atomic_set(&iolat->scale_cookie, | |
876 | atomic_read(&parent->child_lat.scale_cookie)); | |
877 | } else { | |
878 | atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE); | |
879 | } | |
880 | ||
881 | atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE); | |
882 | } | |
883 | ||
884 | static void iolatency_pd_offline(struct blkg_policy_data *pd) | |
885 | { | |
886 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
887 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
888 | ||
889 | iolatency_set_min_lat_nsec(blkg, 0); | |
890 | iolatency_clear_scaling(blkg); | |
891 | } | |
892 | ||
893 | static void iolatency_pd_free(struct blkg_policy_data *pd) | |
894 | { | |
895 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
896 | free_percpu(iolat->stats); | |
897 | kfree(iolat); | |
898 | } | |
899 | ||
900 | static struct cftype iolatency_files[] = { | |
901 | { | |
902 | .name = "latency", | |
903 | .flags = CFTYPE_NOT_ON_ROOT, | |
904 | .seq_show = iolatency_print_limit, | |
905 | .write = iolatency_set_limit, | |
906 | }, | |
907 | {} | |
908 | }; | |
909 | ||
910 | static struct blkcg_policy blkcg_policy_iolatency = { | |
911 | .dfl_cftypes = iolatency_files, | |
912 | .pd_alloc_fn = iolatency_pd_alloc, | |
913 | .pd_init_fn = iolatency_pd_init, | |
914 | .pd_offline_fn = iolatency_pd_offline, | |
915 | .pd_free_fn = iolatency_pd_free, | |
916 | .pd_stat_fn = iolatency_pd_stat, | |
917 | }; | |
918 | ||
919 | static int __init iolatency_init(void) | |
920 | { | |
921 | return blkcg_policy_register(&blkcg_policy_iolatency); | |
922 | } | |
923 | ||
924 | static void __exit iolatency_exit(void) | |
925 | { | |
926 | return blkcg_policy_unregister(&blkcg_policy_iolatency); | |
927 | } | |
928 | ||
929 | module_init(iolatency_init); | |
930 | module_exit(iolatency_exit); |