i2c: refactor function to release a DMA safe buffer
[linux/fpc-iii.git] / block / blk-iolatency.c
blob19923f8a029ddf199e01a7571914e8217f70b308
1 /*
2 * Block rq-qos base io controller
4 * This works similar to wbt with a few exceptions
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 UINT_MAX so
13 * that 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.
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.
22 * Consider the following
24 * root blkg
25 * / \
26 * fast (target=5ms) slow (target=10ms)
27 * / \ / \
28 * a b normal(15ms) unloved
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.
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.
40 * There are 2 ways we throttle IO.
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.
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
54 * total_time += min_lat_nsec - actual_io_completion
56 * and then at throttle time will do
58 * throttle_time = min(total_time, NSEC_PER_SEC)
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.
64 * Copyright (C) 2018 Josef Bacik
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/loadavg.h>
73 #include <linux/sched/signal.h>
74 #include <trace/events/block.h>
75 #include "blk-rq-qos.h"
76 #include "blk-stat.h"
78 #define DEFAULT_SCALE_COOKIE 1000000U
80 static struct blkcg_policy blkcg_policy_iolatency;
81 struct iolatency_grp;
83 struct blk_iolatency {
84 struct rq_qos rqos;
85 struct timer_list timer;
86 atomic_t enabled;
89 static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos)
91 return container_of(rqos, struct blk_iolatency, rqos);
94 static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat)
96 return atomic_read(&blkiolat->enabled) > 0;
99 struct child_latency_info {
100 spinlock_t lock;
102 /* Last time we adjusted the scale of everybody. */
103 u64 last_scale_event;
105 /* The latency that we missed. */
106 u64 scale_lat;
108 /* Total io's from all of our children for the last summation. */
109 u64 nr_samples;
111 /* The guy who actually changed the latency numbers. */
112 struct iolatency_grp *scale_grp;
114 /* Cookie to tell if we need to scale up or down. */
115 atomic_t scale_cookie;
118 struct iolatency_grp {
119 struct blkg_policy_data pd;
120 struct blk_rq_stat __percpu *stats;
121 struct blk_iolatency *blkiolat;
122 struct rq_depth rq_depth;
123 struct rq_wait rq_wait;
124 atomic64_t window_start;
125 atomic_t scale_cookie;
126 u64 min_lat_nsec;
127 u64 cur_win_nsec;
129 /* total running average of our io latency. */
130 u64 lat_avg;
132 /* Our current number of IO's for the last summation. */
133 u64 nr_samples;
135 struct child_latency_info child_lat;
138 #define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC)
139 #define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC
141 * These are the constants used to fake the fixed-point moving average
142 * calculation just like load average. The call to CALC_LOAD folds
143 * (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling
144 * window size is bucketed to try to approximately calculate average
145 * latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows
146 * elapse immediately. Note, windows only elapse with IO activity. Idle
147 * periods extend the most recent window.
149 #define BLKIOLATENCY_NR_EXP_FACTORS 5
150 #define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \
151 (BLKIOLATENCY_NR_EXP_FACTORS - 1))
152 static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = {
153 2045, // exp(1/600) - 600 samples
154 2039, // exp(1/240) - 240 samples
155 2031, // exp(1/120) - 120 samples
156 2023, // exp(1/80) - 80 samples
157 2014, // exp(1/60) - 60 samples
160 static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd)
162 return pd ? container_of(pd, struct iolatency_grp, pd) : NULL;
165 static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg)
167 return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency));
170 static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat)
172 return pd_to_blkg(&iolat->pd);
175 static inline bool iolatency_may_queue(struct iolatency_grp *iolat,
176 wait_queue_entry_t *wait,
177 bool first_block)
179 struct rq_wait *rqw = &iolat->rq_wait;
181 if (first_block && waitqueue_active(&rqw->wait) &&
182 rqw->wait.head.next != &wait->entry)
183 return false;
184 return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth);
187 static void __blkcg_iolatency_throttle(struct rq_qos *rqos,
188 struct iolatency_grp *iolat,
189 spinlock_t *lock, bool issue_as_root,
190 bool use_memdelay)
191 __releases(lock)
192 __acquires(lock)
194 struct rq_wait *rqw = &iolat->rq_wait;
195 unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay);
196 DEFINE_WAIT(wait);
197 bool first_block = true;
199 if (use_delay)
200 blkcg_schedule_throttle(rqos->q, use_memdelay);
203 * To avoid priority inversions we want to just take a slot if we are
204 * issuing as root. If we're being killed off there's no point in
205 * delaying things, we may have been killed by OOM so throttling may
206 * make recovery take even longer, so just let the IO's through so the
207 * task can go away.
209 if (issue_as_root || fatal_signal_pending(current)) {
210 atomic_inc(&rqw->inflight);
211 return;
214 if (iolatency_may_queue(iolat, &wait, first_block))
215 return;
217 do {
218 prepare_to_wait_exclusive(&rqw->wait, &wait,
219 TASK_UNINTERRUPTIBLE);
221 if (iolatency_may_queue(iolat, &wait, first_block))
222 break;
223 first_block = false;
225 if (lock) {
226 spin_unlock_irq(lock);
227 io_schedule();
228 spin_lock_irq(lock);
229 } else {
230 io_schedule();
232 } while (1);
234 finish_wait(&rqw->wait, &wait);
237 #define SCALE_DOWN_FACTOR 2
238 #define SCALE_UP_FACTOR 4
240 static inline unsigned long scale_amount(unsigned long qd, bool up)
242 return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL);
246 * We scale the qd down faster than we scale up, so we need to use this helper
247 * to adjust the scale_cookie accordingly so we don't prematurely get
248 * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much.
250 * Each group has their own local copy of the last scale cookie they saw, so if
251 * the global scale cookie goes up or down they know which way they need to go
252 * based on their last knowledge of it.
254 static void scale_cookie_change(struct blk_iolatency *blkiolat,
255 struct child_latency_info *lat_info,
256 bool up)
258 unsigned long qd = blk_queue_depth(blkiolat->rqos.q);
259 unsigned long scale = scale_amount(qd, up);
260 unsigned long old = atomic_read(&lat_info->scale_cookie);
261 unsigned long max_scale = qd << 1;
262 unsigned long diff = 0;
264 if (old < DEFAULT_SCALE_COOKIE)
265 diff = DEFAULT_SCALE_COOKIE - old;
267 if (up) {
268 if (scale + old > DEFAULT_SCALE_COOKIE)
269 atomic_set(&lat_info->scale_cookie,
270 DEFAULT_SCALE_COOKIE);
271 else if (diff > qd)
272 atomic_inc(&lat_info->scale_cookie);
273 else
274 atomic_add(scale, &lat_info->scale_cookie);
275 } else {
277 * We don't want to dig a hole so deep that it takes us hours to
278 * dig out of it. Just enough that we don't throttle/unthrottle
279 * with jagged workloads but can still unthrottle once pressure
280 * has sufficiently dissipated.
282 if (diff > qd) {
283 if (diff < max_scale)
284 atomic_dec(&lat_info->scale_cookie);
285 } else {
286 atomic_sub(scale, &lat_info->scale_cookie);
292 * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the
293 * queue depth at a time so we don't get wild swings and hopefully dial in to
294 * fairer distribution of the overall queue depth.
296 static void scale_change(struct iolatency_grp *iolat, bool up)
298 unsigned long qd = blk_queue_depth(iolat->blkiolat->rqos.q);
299 unsigned long scale = scale_amount(qd, up);
300 unsigned long old = iolat->rq_depth.max_depth;
301 bool changed = false;
303 if (old > qd)
304 old = qd;
306 if (up) {
307 if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat)))
308 return;
310 if (old < qd) {
311 changed = true;
312 old += scale;
313 old = min(old, qd);
314 iolat->rq_depth.max_depth = old;
315 wake_up_all(&iolat->rq_wait.wait);
317 } else if (old > 1) {
318 old >>= 1;
319 changed = true;
320 iolat->rq_depth.max_depth = max(old, 1UL);
324 /* Check our parent and see if the scale cookie has changed. */
325 static void check_scale_change(struct iolatency_grp *iolat)
327 struct iolatency_grp *parent;
328 struct child_latency_info *lat_info;
329 unsigned int cur_cookie;
330 unsigned int our_cookie = atomic_read(&iolat->scale_cookie);
331 u64 scale_lat;
332 unsigned int old;
333 int direction = 0;
335 if (lat_to_blkg(iolat)->parent == NULL)
336 return;
338 parent = blkg_to_lat(lat_to_blkg(iolat)->parent);
339 if (!parent)
340 return;
342 lat_info = &parent->child_lat;
343 cur_cookie = atomic_read(&lat_info->scale_cookie);
344 scale_lat = READ_ONCE(lat_info->scale_lat);
346 if (cur_cookie < our_cookie)
347 direction = -1;
348 else if (cur_cookie > our_cookie)
349 direction = 1;
350 else
351 return;
353 old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie);
355 /* Somebody beat us to the punch, just bail. */
356 if (old != our_cookie)
357 return;
359 if (direction < 0 && iolat->min_lat_nsec) {
360 u64 samples_thresh;
362 if (!scale_lat || iolat->min_lat_nsec <= scale_lat)
363 return;
366 * Sometimes high priority groups are their own worst enemy, so
367 * instead of taking it out on some poor other group that did 5%
368 * or less of the IO's for the last summation just skip this
369 * scale down event.
371 samples_thresh = lat_info->nr_samples * 5;
372 samples_thresh = div64_u64(samples_thresh, 100);
373 if (iolat->nr_samples <= samples_thresh)
374 return;
377 /* We're as low as we can go. */
378 if (iolat->rq_depth.max_depth == 1 && direction < 0) {
379 blkcg_use_delay(lat_to_blkg(iolat));
380 return;
383 /* We're back to the default cookie, unthrottle all the things. */
384 if (cur_cookie == DEFAULT_SCALE_COOKIE) {
385 blkcg_clear_delay(lat_to_blkg(iolat));
386 iolat->rq_depth.max_depth = UINT_MAX;
387 wake_up_all(&iolat->rq_wait.wait);
388 return;
391 scale_change(iolat, direction > 0);
394 static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio,
395 spinlock_t *lock)
397 struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
398 struct blkcg *blkcg;
399 struct blkcg_gq *blkg;
400 struct request_queue *q = rqos->q;
401 bool issue_as_root = bio_issue_as_root_blkg(bio);
403 if (!blk_iolatency_enabled(blkiolat))
404 return;
406 rcu_read_lock();
407 blkcg = bio_blkcg(bio);
408 bio_associate_blkcg(bio, &blkcg->css);
409 blkg = blkg_lookup(blkcg, q);
410 if (unlikely(!blkg)) {
411 if (!lock)
412 spin_lock_irq(q->queue_lock);
413 blkg = blkg_lookup_create(blkcg, q);
414 if (IS_ERR(blkg))
415 blkg = NULL;
416 if (!lock)
417 spin_unlock_irq(q->queue_lock);
419 if (!blkg)
420 goto out;
422 bio_issue_init(&bio->bi_issue, bio_sectors(bio));
423 bio_associate_blkg(bio, blkg);
424 out:
425 rcu_read_unlock();
426 while (blkg && blkg->parent) {
427 struct iolatency_grp *iolat = blkg_to_lat(blkg);
428 if (!iolat) {
429 blkg = blkg->parent;
430 continue;
433 check_scale_change(iolat);
434 __blkcg_iolatency_throttle(rqos, iolat, lock, issue_as_root,
435 (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
436 blkg = blkg->parent;
438 if (!timer_pending(&blkiolat->timer))
439 mod_timer(&blkiolat->timer, jiffies + HZ);
442 static void iolatency_record_time(struct iolatency_grp *iolat,
443 struct bio_issue *issue, u64 now,
444 bool issue_as_root)
446 struct blk_rq_stat *rq_stat;
447 u64 start = bio_issue_time(issue);
448 u64 req_time;
451 * Have to do this so we are truncated to the correct time that our
452 * issue is truncated to.
454 now = __bio_issue_time(now);
456 if (now <= start)
457 return;
459 req_time = now - start;
462 * We don't want to count issue_as_root bio's in the cgroups latency
463 * statistics as it could skew the numbers downwards.
465 if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) {
466 u64 sub = iolat->min_lat_nsec;
467 if (req_time < sub)
468 blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time);
469 return;
472 rq_stat = get_cpu_ptr(iolat->stats);
473 blk_rq_stat_add(rq_stat, req_time);
474 put_cpu_ptr(rq_stat);
477 #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC)
478 #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5
480 static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now)
482 struct blkcg_gq *blkg = lat_to_blkg(iolat);
483 struct iolatency_grp *parent;
484 struct child_latency_info *lat_info;
485 struct blk_rq_stat stat;
486 unsigned long flags;
487 int cpu, exp_idx;
489 blk_rq_stat_init(&stat);
490 preempt_disable();
491 for_each_online_cpu(cpu) {
492 struct blk_rq_stat *s;
493 s = per_cpu_ptr(iolat->stats, cpu);
494 blk_rq_stat_sum(&stat, s);
495 blk_rq_stat_init(s);
497 preempt_enable();
499 parent = blkg_to_lat(blkg->parent);
500 if (!parent)
501 return;
503 lat_info = &parent->child_lat;
506 * CALC_LOAD takes in a number stored in fixed point representation.
507 * Because we are using this for IO time in ns, the values stored
508 * are significantly larger than the FIXED_1 denominator (2048).
509 * Therefore, rounding errors in the calculation are negligible and
510 * can be ignored.
512 exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1,
513 div64_u64(iolat->cur_win_nsec,
514 BLKIOLATENCY_EXP_BUCKET_SIZE));
515 CALC_LOAD(iolat->lat_avg, iolatency_exp_factors[exp_idx], stat.mean);
517 /* Everything is ok and we don't need to adjust the scale. */
518 if (stat.mean <= iolat->min_lat_nsec &&
519 atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE)
520 return;
522 /* Somebody beat us to the punch, just bail. */
523 spin_lock_irqsave(&lat_info->lock, flags);
524 lat_info->nr_samples -= iolat->nr_samples;
525 lat_info->nr_samples += stat.nr_samples;
526 iolat->nr_samples = stat.nr_samples;
528 if ((lat_info->last_scale_event >= now ||
529 now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME) &&
530 lat_info->scale_lat <= iolat->min_lat_nsec)
531 goto out;
533 if (stat.mean <= iolat->min_lat_nsec &&
534 stat.nr_samples >= BLKIOLATENCY_MIN_GOOD_SAMPLES) {
535 if (lat_info->scale_grp == iolat) {
536 lat_info->last_scale_event = now;
537 scale_cookie_change(iolat->blkiolat, lat_info, true);
539 } else if (stat.mean > iolat->min_lat_nsec) {
540 lat_info->last_scale_event = now;
541 if (!lat_info->scale_grp ||
542 lat_info->scale_lat > iolat->min_lat_nsec) {
543 WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec);
544 lat_info->scale_grp = iolat;
546 scale_cookie_change(iolat->blkiolat, lat_info, false);
548 out:
549 spin_unlock_irqrestore(&lat_info->lock, flags);
552 static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
554 struct blkcg_gq *blkg;
555 struct rq_wait *rqw;
556 struct iolatency_grp *iolat;
557 u64 window_start;
558 u64 now = ktime_to_ns(ktime_get());
559 bool issue_as_root = bio_issue_as_root_blkg(bio);
560 bool enabled = false;
562 blkg = bio->bi_blkg;
563 if (!blkg)
564 return;
566 iolat = blkg_to_lat(bio->bi_blkg);
567 if (!iolat)
568 return;
570 enabled = blk_iolatency_enabled(iolat->blkiolat);
571 while (blkg && blkg->parent) {
572 iolat = blkg_to_lat(blkg);
573 if (!iolat) {
574 blkg = blkg->parent;
575 continue;
577 rqw = &iolat->rq_wait;
579 atomic_dec(&rqw->inflight);
580 if (!enabled || iolat->min_lat_nsec == 0)
581 goto next;
582 iolatency_record_time(iolat, &bio->bi_issue, now,
583 issue_as_root);
584 window_start = atomic64_read(&iolat->window_start);
585 if (now > window_start &&
586 (now - window_start) >= iolat->cur_win_nsec) {
587 if (atomic64_cmpxchg(&iolat->window_start,
588 window_start, now) == window_start)
589 iolatency_check_latencies(iolat, now);
591 next:
592 wake_up(&rqw->wait);
593 blkg = blkg->parent;
597 static void blkcg_iolatency_cleanup(struct rq_qos *rqos, struct bio *bio)
599 struct blkcg_gq *blkg;
601 blkg = bio->bi_blkg;
602 while (blkg && blkg->parent) {
603 struct rq_wait *rqw;
604 struct iolatency_grp *iolat;
606 iolat = blkg_to_lat(blkg);
607 if (!iolat)
608 goto next;
610 rqw = &iolat->rq_wait;
611 atomic_dec(&rqw->inflight);
612 wake_up(&rqw->wait);
613 next:
614 blkg = blkg->parent;
618 static void blkcg_iolatency_exit(struct rq_qos *rqos)
620 struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
622 del_timer_sync(&blkiolat->timer);
623 blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency);
624 kfree(blkiolat);
627 static struct rq_qos_ops blkcg_iolatency_ops = {
628 .throttle = blkcg_iolatency_throttle,
629 .cleanup = blkcg_iolatency_cleanup,
630 .done_bio = blkcg_iolatency_done_bio,
631 .exit = blkcg_iolatency_exit,
634 static void blkiolatency_timer_fn(struct timer_list *t)
636 struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer);
637 struct blkcg_gq *blkg;
638 struct cgroup_subsys_state *pos_css;
639 u64 now = ktime_to_ns(ktime_get());
641 rcu_read_lock();
642 blkg_for_each_descendant_pre(blkg, pos_css,
643 blkiolat->rqos.q->root_blkg) {
644 struct iolatency_grp *iolat;
645 struct child_latency_info *lat_info;
646 unsigned long flags;
647 u64 cookie;
650 * We could be exiting, don't access the pd unless we have a
651 * ref on the blkg.
653 if (!blkg_try_get(blkg))
654 continue;
656 iolat = blkg_to_lat(blkg);
657 if (!iolat)
658 goto next;
660 lat_info = &iolat->child_lat;
661 cookie = atomic_read(&lat_info->scale_cookie);
663 if (cookie >= DEFAULT_SCALE_COOKIE)
664 goto next;
666 spin_lock_irqsave(&lat_info->lock, flags);
667 if (lat_info->last_scale_event >= now)
668 goto next_lock;
671 * We scaled down but don't have a scale_grp, scale up and carry
672 * on.
674 if (lat_info->scale_grp == NULL) {
675 scale_cookie_change(iolat->blkiolat, lat_info, true);
676 goto next_lock;
680 * It's been 5 seconds since our last scale event, clear the
681 * scale grp in case the group that needed the scale down isn't
682 * doing any IO currently.
684 if (now - lat_info->last_scale_event >=
685 ((u64)NSEC_PER_SEC * 5))
686 lat_info->scale_grp = NULL;
687 next_lock:
688 spin_unlock_irqrestore(&lat_info->lock, flags);
689 next:
690 blkg_put(blkg);
692 rcu_read_unlock();
695 int blk_iolatency_init(struct request_queue *q)
697 struct blk_iolatency *blkiolat;
698 struct rq_qos *rqos;
699 int ret;
701 blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL);
702 if (!blkiolat)
703 return -ENOMEM;
705 rqos = &blkiolat->rqos;
706 rqos->id = RQ_QOS_CGROUP;
707 rqos->ops = &blkcg_iolatency_ops;
708 rqos->q = q;
710 rq_qos_add(q, rqos);
712 ret = blkcg_activate_policy(q, &blkcg_policy_iolatency);
713 if (ret) {
714 rq_qos_del(q, rqos);
715 kfree(blkiolat);
716 return ret;
719 timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0);
721 return 0;
724 static void iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val)
726 struct iolatency_grp *iolat = blkg_to_lat(blkg);
727 struct blk_iolatency *blkiolat = iolat->blkiolat;
728 u64 oldval = iolat->min_lat_nsec;
730 iolat->min_lat_nsec = val;
731 iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE);
732 iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec,
733 BLKIOLATENCY_MAX_WIN_SIZE);
735 if (!oldval && val)
736 atomic_inc(&blkiolat->enabled);
737 if (oldval && !val)
738 atomic_dec(&blkiolat->enabled);
741 static void iolatency_clear_scaling(struct blkcg_gq *blkg)
743 if (blkg->parent) {
744 struct iolatency_grp *iolat = blkg_to_lat(blkg->parent);
745 struct child_latency_info *lat_info;
746 if (!iolat)
747 return;
749 lat_info = &iolat->child_lat;
750 spin_lock(&lat_info->lock);
751 atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE);
752 lat_info->last_scale_event = 0;
753 lat_info->scale_grp = NULL;
754 lat_info->scale_lat = 0;
755 spin_unlock(&lat_info->lock);
759 static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
760 size_t nbytes, loff_t off)
762 struct blkcg *blkcg = css_to_blkcg(of_css(of));
763 struct blkcg_gq *blkg;
764 struct blk_iolatency *blkiolat;
765 struct blkg_conf_ctx ctx;
766 struct iolatency_grp *iolat;
767 char *p, *tok;
768 u64 lat_val = 0;
769 u64 oldval;
770 int ret;
772 ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx);
773 if (ret)
774 return ret;
776 iolat = blkg_to_lat(ctx.blkg);
777 blkiolat = iolat->blkiolat;
778 p = ctx.body;
780 ret = -EINVAL;
781 while ((tok = strsep(&p, " "))) {
782 char key[16];
783 char val[21]; /* 18446744073709551616 */
785 if (sscanf(tok, "%15[^=]=%20s", key, val) != 2)
786 goto out;
788 if (!strcmp(key, "target")) {
789 u64 v;
791 if (!strcmp(val, "max"))
792 lat_val = 0;
793 else if (sscanf(val, "%llu", &v) == 1)
794 lat_val = v * NSEC_PER_USEC;
795 else
796 goto out;
797 } else {
798 goto out;
802 /* Walk up the tree to see if our new val is lower than it should be. */
803 blkg = ctx.blkg;
804 oldval = iolat->min_lat_nsec;
806 iolatency_set_min_lat_nsec(blkg, lat_val);
807 if (oldval != iolat->min_lat_nsec) {
808 iolatency_clear_scaling(blkg);
811 ret = 0;
812 out:
813 blkg_conf_finish(&ctx);
814 return ret ?: nbytes;
817 static u64 iolatency_prfill_limit(struct seq_file *sf,
818 struct blkg_policy_data *pd, int off)
820 struct iolatency_grp *iolat = pd_to_lat(pd);
821 const char *dname = blkg_dev_name(pd->blkg);
823 if (!dname || !iolat->min_lat_nsec)
824 return 0;
825 seq_printf(sf, "%s target=%llu\n",
826 dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC));
827 return 0;
830 static int iolatency_print_limit(struct seq_file *sf, void *v)
832 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
833 iolatency_prfill_limit,
834 &blkcg_policy_iolatency, seq_cft(sf)->private, false);
835 return 0;
838 static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf,
839 size_t size)
841 struct iolatency_grp *iolat = pd_to_lat(pd);
842 unsigned long long avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC);
843 unsigned long long cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC);
845 if (iolat->rq_depth.max_depth == UINT_MAX)
846 return scnprintf(buf, size, " depth=max avg_lat=%llu win=%llu",
847 avg_lat, cur_win);
849 return scnprintf(buf, size, " depth=%u avg_lat=%llu win=%llu",
850 iolat->rq_depth.max_depth, avg_lat, cur_win);
854 static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, int node)
856 struct iolatency_grp *iolat;
858 iolat = kzalloc_node(sizeof(*iolat), gfp, node);
859 if (!iolat)
860 return NULL;
861 iolat->stats = __alloc_percpu_gfp(sizeof(struct blk_rq_stat),
862 __alignof__(struct blk_rq_stat), gfp);
863 if (!iolat->stats) {
864 kfree(iolat);
865 return NULL;
867 return &iolat->pd;
870 static void iolatency_pd_init(struct blkg_policy_data *pd)
872 struct iolatency_grp *iolat = pd_to_lat(pd);
873 struct blkcg_gq *blkg = lat_to_blkg(iolat);
874 struct rq_qos *rqos = blkcg_rq_qos(blkg->q);
875 struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
876 u64 now = ktime_to_ns(ktime_get());
877 int cpu;
879 for_each_possible_cpu(cpu) {
880 struct blk_rq_stat *stat;
881 stat = per_cpu_ptr(iolat->stats, cpu);
882 blk_rq_stat_init(stat);
885 rq_wait_init(&iolat->rq_wait);
886 spin_lock_init(&iolat->child_lat.lock);
887 iolat->rq_depth.queue_depth = blk_queue_depth(blkg->q);
888 iolat->rq_depth.max_depth = UINT_MAX;
889 iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth;
890 iolat->blkiolat = blkiolat;
891 iolat->cur_win_nsec = 100 * NSEC_PER_MSEC;
892 atomic64_set(&iolat->window_start, now);
895 * We init things in list order, so the pd for the parent may not be
896 * init'ed yet for whatever reason.
898 if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) {
899 struct iolatency_grp *parent = blkg_to_lat(blkg->parent);
900 atomic_set(&iolat->scale_cookie,
901 atomic_read(&parent->child_lat.scale_cookie));
902 } else {
903 atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE);
906 atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE);
909 static void iolatency_pd_offline(struct blkg_policy_data *pd)
911 struct iolatency_grp *iolat = pd_to_lat(pd);
912 struct blkcg_gq *blkg = lat_to_blkg(iolat);
914 iolatency_set_min_lat_nsec(blkg, 0);
915 iolatency_clear_scaling(blkg);
918 static void iolatency_pd_free(struct blkg_policy_data *pd)
920 struct iolatency_grp *iolat = pd_to_lat(pd);
921 free_percpu(iolat->stats);
922 kfree(iolat);
925 static struct cftype iolatency_files[] = {
927 .name = "latency",
928 .flags = CFTYPE_NOT_ON_ROOT,
929 .seq_show = iolatency_print_limit,
930 .write = iolatency_set_limit,
935 static struct blkcg_policy blkcg_policy_iolatency = {
936 .dfl_cftypes = iolatency_files,
937 .pd_alloc_fn = iolatency_pd_alloc,
938 .pd_init_fn = iolatency_pd_init,
939 .pd_offline_fn = iolatency_pd_offline,
940 .pd_free_fn = iolatency_pd_free,
941 .pd_stat_fn = iolatency_pd_stat,
944 static int __init iolatency_init(void)
946 return blkcg_policy_register(&blkcg_policy_iolatency);
949 static void __exit iolatency_exit(void)
951 return blkcg_policy_unregister(&blkcg_policy_iolatency);
954 module_init(iolatency_init);
955 module_exit(iolatency_exit);