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3dcf60bc | 1 | // SPDX-License-Identifier: GPL-2.0 |
d7067512 JB |
2 | /* |
3 | * Block rq-qos base io controller | |
4 | * | |
5 | * This works similar to wbt with a few exceptions | |
6 | * | |
7 | * - It's bio based, so the latency covers the whole block layer in addition to | |
8 | * the actual io. | |
9 | * - We will throttle all IO that comes in here if we need to. | |
10 | * - We use the mean latency over the 100ms window. This is because writes can | |
11 | * be particularly fast, which could give us a false sense of the impact of | |
12 | * other workloads on our protected workload. | |
a284390b JB |
13 | * - By default there's no throttling, we set the queue_depth to UINT_MAX so |
14 | * that we can have as many outstanding bio's as we're allowed to. Only at | |
d7067512 JB |
15 | * throttle time do we pay attention to the actual queue depth. |
16 | * | |
17 | * The hierarchy works like the cpu controller does, we track the latency at | |
18 | * every configured node, and each configured node has it's own independent | |
19 | * queue depth. This means that we only care about our latency targets at the | |
20 | * peer level. Some group at the bottom of the hierarchy isn't going to affect | |
21 | * a group at the end of some other path if we're only configred at leaf level. | |
22 | * | |
23 | * Consider the following | |
24 | * | |
25 | * root blkg | |
26 | * / \ | |
27 | * fast (target=5ms) slow (target=10ms) | |
28 | * / \ / \ | |
29 | * a b normal(15ms) unloved | |
30 | * | |
31 | * "a" and "b" have no target, but their combined io under "fast" cannot exceed | |
32 | * an average latency of 5ms. If it does then we will throttle the "slow" | |
33 | * group. In the case of "normal", if it exceeds its 15ms target, we will | |
34 | * throttle "unloved", but nobody else. | |
35 | * | |
36 | * In this example "fast", "slow", and "normal" will be the only groups actually | |
37 | * accounting their io latencies. We have to walk up the heirarchy to the root | |
38 | * on every submit and complete so we can do the appropriate stat recording and | |
39 | * adjust the queue depth of ourselves if needed. | |
40 | * | |
41 | * There are 2 ways we throttle IO. | |
42 | * | |
43 | * 1) Queue depth throttling. As we throttle down we will adjust the maximum | |
44 | * number of IO's we're allowed to have in flight. This starts at (u64)-1 down | |
45 | * to 1. If the group is only ever submitting IO for itself then this is the | |
46 | * only way we throttle. | |
47 | * | |
48 | * 2) Induced delay throttling. This is for the case that a group is generating | |
49 | * IO that has to be issued by the root cg to avoid priority inversion. So think | |
50 | * REQ_META or REQ_SWAP. If we are already at qd == 1 and we're getting a lot | |
51 | * of work done for us on behalf of the root cg and are being asked to scale | |
52 | * down more then we induce a latency at userspace return. We accumulate the | |
53 | * total amount of time we need to be punished by doing | |
54 | * | |
55 | * total_time += min_lat_nsec - actual_io_completion | |
56 | * | |
57 | * and then at throttle time will do | |
58 | * | |
59 | * throttle_time = min(total_time, NSEC_PER_SEC) | |
60 | * | |
61 | * This induced delay will throttle back the activity that is generating the | |
62 | * root cg issued io's, wethere that's some metadata intensive operation or the | |
63 | * group is using so much memory that it is pushing us into swap. | |
64 | * | |
65 | * Copyright (C) 2018 Josef Bacik | |
66 | */ | |
67 | #include <linux/kernel.h> | |
68 | #include <linux/blk_types.h> | |
69 | #include <linux/backing-dev.h> | |
70 | #include <linux/module.h> | |
71 | #include <linux/timer.h> | |
72 | #include <linux/memcontrol.h> | |
c480bcf9 | 73 | #include <linux/sched/loadavg.h> |
d7067512 JB |
74 | #include <linux/sched/signal.h> |
75 | #include <trace/events/block.h> | |
8c772a9b | 76 | #include <linux/blk-mq.h> |
d7067512 JB |
77 | #include "blk-rq-qos.h" |
78 | #include "blk-stat.h" | |
373e915c | 79 | #include "blk.h" |
d7067512 JB |
80 | |
81 | #define DEFAULT_SCALE_COOKIE 1000000U | |
82 | ||
83 | static struct blkcg_policy blkcg_policy_iolatency; | |
84 | struct iolatency_grp; | |
85 | ||
86 | struct blk_iolatency { | |
87 | struct rq_qos rqos; | |
88 | struct timer_list timer; | |
89 | atomic_t enabled; | |
90 | }; | |
91 | ||
92 | static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) | |
93 | { | |
94 | return container_of(rqos, struct blk_iolatency, rqos); | |
95 | } | |
96 | ||
97 | static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat) | |
98 | { | |
99 | return atomic_read(&blkiolat->enabled) > 0; | |
100 | } | |
101 | ||
102 | struct child_latency_info { | |
103 | spinlock_t lock; | |
104 | ||
105 | /* Last time we adjusted the scale of everybody. */ | |
106 | u64 last_scale_event; | |
107 | ||
108 | /* The latency that we missed. */ | |
109 | u64 scale_lat; | |
110 | ||
111 | /* Total io's from all of our children for the last summation. */ | |
112 | u64 nr_samples; | |
113 | ||
114 | /* The guy who actually changed the latency numbers. */ | |
115 | struct iolatency_grp *scale_grp; | |
116 | ||
117 | /* Cookie to tell if we need to scale up or down. */ | |
118 | atomic_t scale_cookie; | |
119 | }; | |
120 | ||
1fa2840e JB |
121 | struct percentile_stats { |
122 | u64 total; | |
123 | u64 missed; | |
124 | }; | |
125 | ||
126 | struct latency_stat { | |
127 | union { | |
128 | struct percentile_stats ps; | |
129 | struct blk_rq_stat rqs; | |
130 | }; | |
131 | }; | |
132 | ||
d7067512 JB |
133 | struct iolatency_grp { |
134 | struct blkg_policy_data pd; | |
1fa2840e | 135 | struct latency_stat __percpu *stats; |
451bb7c3 | 136 | struct latency_stat cur_stat; |
d7067512 JB |
137 | struct blk_iolatency *blkiolat; |
138 | struct rq_depth rq_depth; | |
139 | struct rq_wait rq_wait; | |
140 | atomic64_t window_start; | |
141 | atomic_t scale_cookie; | |
142 | u64 min_lat_nsec; | |
143 | u64 cur_win_nsec; | |
144 | ||
145 | /* total running average of our io latency. */ | |
c480bcf9 | 146 | u64 lat_avg; |
d7067512 JB |
147 | |
148 | /* Our current number of IO's for the last summation. */ | |
149 | u64 nr_samples; | |
150 | ||
1fa2840e | 151 | bool ssd; |
d7067512 JB |
152 | struct child_latency_info child_lat; |
153 | }; | |
154 | ||
c480bcf9 DZF |
155 | #define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC) |
156 | #define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC | |
157 | /* | |
158 | * These are the constants used to fake the fixed-point moving average | |
8508cf3f | 159 | * calculation just like load average. The call to calc_load() folds |
c480bcf9 DZF |
160 | * (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling |
161 | * window size is bucketed to try to approximately calculate average | |
162 | * latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows | |
163 | * elapse immediately. Note, windows only elapse with IO activity. Idle | |
164 | * periods extend the most recent window. | |
165 | */ | |
166 | #define BLKIOLATENCY_NR_EXP_FACTORS 5 | |
167 | #define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \ | |
168 | (BLKIOLATENCY_NR_EXP_FACTORS - 1)) | |
169 | static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = { | |
170 | 2045, // exp(1/600) - 600 samples | |
171 | 2039, // exp(1/240) - 240 samples | |
172 | 2031, // exp(1/120) - 120 samples | |
173 | 2023, // exp(1/80) - 80 samples | |
174 | 2014, // exp(1/60) - 60 samples | |
175 | }; | |
176 | ||
d7067512 JB |
177 | static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd) |
178 | { | |
179 | return pd ? container_of(pd, struct iolatency_grp, pd) : NULL; | |
180 | } | |
181 | ||
182 | static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg) | |
183 | { | |
184 | return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency)); | |
185 | } | |
186 | ||
187 | static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat) | |
188 | { | |
189 | return pd_to_blkg(&iolat->pd); | |
190 | } | |
191 | ||
1fa2840e JB |
192 | static inline void latency_stat_init(struct iolatency_grp *iolat, |
193 | struct latency_stat *stat) | |
194 | { | |
195 | if (iolat->ssd) { | |
196 | stat->ps.total = 0; | |
197 | stat->ps.missed = 0; | |
198 | } else | |
199 | blk_rq_stat_init(&stat->rqs); | |
200 | } | |
201 | ||
202 | static inline void latency_stat_sum(struct iolatency_grp *iolat, | |
203 | struct latency_stat *sum, | |
204 | struct latency_stat *stat) | |
205 | { | |
206 | if (iolat->ssd) { | |
207 | sum->ps.total += stat->ps.total; | |
208 | sum->ps.missed += stat->ps.missed; | |
209 | } else | |
210 | blk_rq_stat_sum(&sum->rqs, &stat->rqs); | |
211 | } | |
212 | ||
213 | static inline void latency_stat_record_time(struct iolatency_grp *iolat, | |
214 | u64 req_time) | |
215 | { | |
216 | struct latency_stat *stat = get_cpu_ptr(iolat->stats); | |
217 | if (iolat->ssd) { | |
218 | if (req_time >= iolat->min_lat_nsec) | |
219 | stat->ps.missed++; | |
220 | stat->ps.total++; | |
221 | } else | |
222 | blk_rq_stat_add(&stat->rqs, req_time); | |
223 | put_cpu_ptr(stat); | |
224 | } | |
225 | ||
226 | static inline bool latency_sum_ok(struct iolatency_grp *iolat, | |
227 | struct latency_stat *stat) | |
228 | { | |
229 | if (iolat->ssd) { | |
230 | u64 thresh = div64_u64(stat->ps.total, 10); | |
231 | thresh = max(thresh, 1ULL); | |
232 | return stat->ps.missed < thresh; | |
233 | } | |
234 | return stat->rqs.mean <= iolat->min_lat_nsec; | |
235 | } | |
236 | ||
237 | static inline u64 latency_stat_samples(struct iolatency_grp *iolat, | |
238 | struct latency_stat *stat) | |
239 | { | |
240 | if (iolat->ssd) | |
241 | return stat->ps.total; | |
242 | return stat->rqs.nr_samples; | |
243 | } | |
244 | ||
245 | static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat, | |
246 | struct latency_stat *stat) | |
247 | { | |
248 | int exp_idx; | |
249 | ||
250 | if (iolat->ssd) | |
251 | return; | |
252 | ||
253 | /* | |
8508cf3f | 254 | * calc_load() takes in a number stored in fixed point representation. |
1fa2840e JB |
255 | * Because we are using this for IO time in ns, the values stored |
256 | * are significantly larger than the FIXED_1 denominator (2048). | |
257 | * Therefore, rounding errors in the calculation are negligible and | |
258 | * can be ignored. | |
259 | */ | |
260 | exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1, | |
261 | div64_u64(iolat->cur_win_nsec, | |
262 | BLKIOLATENCY_EXP_BUCKET_SIZE)); | |
8508cf3f JW |
263 | iolat->lat_avg = calc_load(iolat->lat_avg, |
264 | iolatency_exp_factors[exp_idx], | |
265 | stat->rqs.mean); | |
1fa2840e JB |
266 | } |
267 | ||
d3fcdff1 | 268 | static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data) |
d7067512 | 269 | { |
d3fcdff1 JB |
270 | atomic_dec(&rqw->inflight); |
271 | wake_up(&rqw->wait); | |
272 | } | |
d7067512 | 273 | |
d3fcdff1 JB |
274 | static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data) |
275 | { | |
276 | struct iolatency_grp *iolat = private_data; | |
d7067512 JB |
277 | return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth); |
278 | } | |
279 | ||
280 | static void __blkcg_iolatency_throttle(struct rq_qos *rqos, | |
281 | struct iolatency_grp *iolat, | |
d5337560 | 282 | bool issue_as_root, |
d7067512 | 283 | bool use_memdelay) |
d7067512 JB |
284 | { |
285 | struct rq_wait *rqw = &iolat->rq_wait; | |
286 | unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay); | |
d7067512 JB |
287 | |
288 | if (use_delay) | |
289 | blkcg_schedule_throttle(rqos->q, use_memdelay); | |
290 | ||
291 | /* | |
292 | * To avoid priority inversions we want to just take a slot if we are | |
293 | * issuing as root. If we're being killed off there's no point in | |
294 | * delaying things, we may have been killed by OOM so throttling may | |
295 | * make recovery take even longer, so just let the IO's through so the | |
296 | * task can go away. | |
297 | */ | |
298 | if (issue_as_root || fatal_signal_pending(current)) { | |
299 | atomic_inc(&rqw->inflight); | |
300 | return; | |
301 | } | |
302 | ||
d3fcdff1 | 303 | rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb); |
d7067512 JB |
304 | } |
305 | ||
306 | #define SCALE_DOWN_FACTOR 2 | |
307 | #define SCALE_UP_FACTOR 4 | |
308 | ||
309 | static inline unsigned long scale_amount(unsigned long qd, bool up) | |
310 | { | |
311 | return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL); | |
312 | } | |
313 | ||
314 | /* | |
315 | * We scale the qd down faster than we scale up, so we need to use this helper | |
316 | * to adjust the scale_cookie accordingly so we don't prematurely get | |
317 | * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much. | |
318 | * | |
319 | * Each group has their own local copy of the last scale cookie they saw, so if | |
320 | * the global scale cookie goes up or down they know which way they need to go | |
321 | * based on their last knowledge of it. | |
322 | */ | |
323 | static void scale_cookie_change(struct blk_iolatency *blkiolat, | |
324 | struct child_latency_info *lat_info, | |
325 | bool up) | |
326 | { | |
ff4cee08 | 327 | unsigned long qd = blkiolat->rqos.q->nr_requests; |
d7067512 JB |
328 | unsigned long scale = scale_amount(qd, up); |
329 | unsigned long old = atomic_read(&lat_info->scale_cookie); | |
330 | unsigned long max_scale = qd << 1; | |
331 | unsigned long diff = 0; | |
332 | ||
333 | if (old < DEFAULT_SCALE_COOKIE) | |
334 | diff = DEFAULT_SCALE_COOKIE - old; | |
335 | ||
336 | if (up) { | |
337 | if (scale + old > DEFAULT_SCALE_COOKIE) | |
338 | atomic_set(&lat_info->scale_cookie, | |
339 | DEFAULT_SCALE_COOKIE); | |
340 | else if (diff > qd) | |
341 | atomic_inc(&lat_info->scale_cookie); | |
342 | else | |
343 | atomic_add(scale, &lat_info->scale_cookie); | |
344 | } else { | |
345 | /* | |
346 | * We don't want to dig a hole so deep that it takes us hours to | |
347 | * dig out of it. Just enough that we don't throttle/unthrottle | |
348 | * with jagged workloads but can still unthrottle once pressure | |
349 | * has sufficiently dissipated. | |
350 | */ | |
351 | if (diff > qd) { | |
352 | if (diff < max_scale) | |
353 | atomic_dec(&lat_info->scale_cookie); | |
354 | } else { | |
355 | atomic_sub(scale, &lat_info->scale_cookie); | |
356 | } | |
357 | } | |
358 | } | |
359 | ||
360 | /* | |
361 | * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the | |
362 | * queue depth at a time so we don't get wild swings and hopefully dial in to | |
363 | * fairer distribution of the overall queue depth. | |
364 | */ | |
365 | static void scale_change(struct iolatency_grp *iolat, bool up) | |
366 | { | |
ff4cee08 | 367 | unsigned long qd = iolat->blkiolat->rqos.q->nr_requests; |
d7067512 JB |
368 | unsigned long scale = scale_amount(qd, up); |
369 | unsigned long old = iolat->rq_depth.max_depth; | |
d7067512 JB |
370 | |
371 | if (old > qd) | |
372 | old = qd; | |
373 | ||
374 | if (up) { | |
375 | if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat))) | |
376 | return; | |
377 | ||
378 | if (old < qd) { | |
d7067512 JB |
379 | old += scale; |
380 | old = min(old, qd); | |
381 | iolat->rq_depth.max_depth = old; | |
382 | wake_up_all(&iolat->rq_wait.wait); | |
383 | } | |
9f60511a | 384 | } else { |
d7067512 | 385 | old >>= 1; |
d7067512 JB |
386 | iolat->rq_depth.max_depth = max(old, 1UL); |
387 | } | |
388 | } | |
389 | ||
390 | /* Check our parent and see if the scale cookie has changed. */ | |
391 | static void check_scale_change(struct iolatency_grp *iolat) | |
392 | { | |
393 | struct iolatency_grp *parent; | |
394 | struct child_latency_info *lat_info; | |
395 | unsigned int cur_cookie; | |
396 | unsigned int our_cookie = atomic_read(&iolat->scale_cookie); | |
397 | u64 scale_lat; | |
398 | unsigned int old; | |
399 | int direction = 0; | |
400 | ||
401 | if (lat_to_blkg(iolat)->parent == NULL) | |
402 | return; | |
403 | ||
404 | parent = blkg_to_lat(lat_to_blkg(iolat)->parent); | |
405 | if (!parent) | |
406 | return; | |
407 | ||
408 | lat_info = &parent->child_lat; | |
409 | cur_cookie = atomic_read(&lat_info->scale_cookie); | |
410 | scale_lat = READ_ONCE(lat_info->scale_lat); | |
411 | ||
412 | if (cur_cookie < our_cookie) | |
413 | direction = -1; | |
414 | else if (cur_cookie > our_cookie) | |
415 | direction = 1; | |
416 | else | |
417 | return; | |
418 | ||
419 | old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie); | |
420 | ||
421 | /* Somebody beat us to the punch, just bail. */ | |
422 | if (old != our_cookie) | |
423 | return; | |
424 | ||
425 | if (direction < 0 && iolat->min_lat_nsec) { | |
426 | u64 samples_thresh; | |
427 | ||
428 | if (!scale_lat || iolat->min_lat_nsec <= scale_lat) | |
429 | return; | |
430 | ||
431 | /* | |
432 | * Sometimes high priority groups are their own worst enemy, so | |
433 | * instead of taking it out on some poor other group that did 5% | |
434 | * or less of the IO's for the last summation just skip this | |
435 | * scale down event. | |
436 | */ | |
437 | samples_thresh = lat_info->nr_samples * 5; | |
22ed8a93 | 438 | samples_thresh = max(1ULL, div64_u64(samples_thresh, 100)); |
d7067512 JB |
439 | if (iolat->nr_samples <= samples_thresh) |
440 | return; | |
441 | } | |
442 | ||
443 | /* We're as low as we can go. */ | |
444 | if (iolat->rq_depth.max_depth == 1 && direction < 0) { | |
445 | blkcg_use_delay(lat_to_blkg(iolat)); | |
446 | return; | |
447 | } | |
448 | ||
449 | /* We're back to the default cookie, unthrottle all the things. */ | |
450 | if (cur_cookie == DEFAULT_SCALE_COOKIE) { | |
451 | blkcg_clear_delay(lat_to_blkg(iolat)); | |
a284390b | 452 | iolat->rq_depth.max_depth = UINT_MAX; |
d7067512 JB |
453 | wake_up_all(&iolat->rq_wait.wait); |
454 | return; | |
455 | } | |
456 | ||
457 | scale_change(iolat, direction > 0); | |
458 | } | |
459 | ||
d5337560 | 460 | static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio) |
d7067512 JB |
461 | { |
462 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
5cdf2e3f | 463 | struct blkcg_gq *blkg = bio->bi_blkg; |
d7067512 JB |
464 | bool issue_as_root = bio_issue_as_root_blkg(bio); |
465 | ||
466 | if (!blk_iolatency_enabled(blkiolat)) | |
467 | return; | |
468 | ||
d7067512 JB |
469 | while (blkg && blkg->parent) { |
470 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
471 | if (!iolat) { | |
472 | blkg = blkg->parent; | |
473 | continue; | |
474 | } | |
475 | ||
476 | check_scale_change(iolat); | |
d5337560 | 477 | __blkcg_iolatency_throttle(rqos, iolat, issue_as_root, |
d7067512 JB |
478 | (bio->bi_opf & REQ_SWAP) == REQ_SWAP); |
479 | blkg = blkg->parent; | |
480 | } | |
481 | if (!timer_pending(&blkiolat->timer)) | |
482 | mod_timer(&blkiolat->timer, jiffies + HZ); | |
483 | } | |
484 | ||
485 | static void iolatency_record_time(struct iolatency_grp *iolat, | |
486 | struct bio_issue *issue, u64 now, | |
487 | bool issue_as_root) | |
488 | { | |
d7067512 JB |
489 | u64 start = bio_issue_time(issue); |
490 | u64 req_time; | |
491 | ||
71e9690b JB |
492 | /* |
493 | * Have to do this so we are truncated to the correct time that our | |
494 | * issue is truncated to. | |
495 | */ | |
496 | now = __bio_issue_time(now); | |
497 | ||
d7067512 JB |
498 | if (now <= start) |
499 | return; | |
500 | ||
501 | req_time = now - start; | |
502 | ||
503 | /* | |
504 | * We don't want to count issue_as_root bio's in the cgroups latency | |
505 | * statistics as it could skew the numbers downwards. | |
506 | */ | |
a284390b | 507 | if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) { |
d7067512 JB |
508 | u64 sub = iolat->min_lat_nsec; |
509 | if (req_time < sub) | |
510 | blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time); | |
511 | return; | |
512 | } | |
513 | ||
1fa2840e | 514 | latency_stat_record_time(iolat, req_time); |
d7067512 JB |
515 | } |
516 | ||
517 | #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC) | |
518 | #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5 | |
519 | ||
520 | static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) | |
521 | { | |
522 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
523 | struct iolatency_grp *parent; | |
524 | struct child_latency_info *lat_info; | |
1fa2840e | 525 | struct latency_stat stat; |
d7067512 | 526 | unsigned long flags; |
1fa2840e | 527 | int cpu; |
d7067512 | 528 | |
1fa2840e | 529 | latency_stat_init(iolat, &stat); |
d7067512 JB |
530 | preempt_disable(); |
531 | for_each_online_cpu(cpu) { | |
1fa2840e | 532 | struct latency_stat *s; |
d7067512 | 533 | s = per_cpu_ptr(iolat->stats, cpu); |
1fa2840e JB |
534 | latency_stat_sum(iolat, &stat, s); |
535 | latency_stat_init(iolat, s); | |
d7067512 JB |
536 | } |
537 | preempt_enable(); | |
538 | ||
d7067512 JB |
539 | parent = blkg_to_lat(blkg->parent); |
540 | if (!parent) | |
541 | return; | |
542 | ||
543 | lat_info = &parent->child_lat; | |
544 | ||
1fa2840e | 545 | iolat_update_total_lat_avg(iolat, &stat); |
d7067512 JB |
546 | |
547 | /* Everything is ok and we don't need to adjust the scale. */ | |
1fa2840e | 548 | if (latency_sum_ok(iolat, &stat) && |
d7067512 JB |
549 | atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE) |
550 | return; | |
551 | ||
552 | /* Somebody beat us to the punch, just bail. */ | |
553 | spin_lock_irqsave(&lat_info->lock, flags); | |
451bb7c3 JB |
554 | |
555 | latency_stat_sum(iolat, &iolat->cur_stat, &stat); | |
d7067512 | 556 | lat_info->nr_samples -= iolat->nr_samples; |
451bb7c3 JB |
557 | lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat); |
558 | iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat); | |
d7067512 JB |
559 | |
560 | if ((lat_info->last_scale_event >= now || | |
451bb7c3 | 561 | now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME)) |
d7067512 JB |
562 | goto out; |
563 | ||
451bb7c3 JB |
564 | if (latency_sum_ok(iolat, &iolat->cur_stat) && |
565 | latency_sum_ok(iolat, &stat)) { | |
566 | if (latency_stat_samples(iolat, &iolat->cur_stat) < | |
1fa2840e JB |
567 | BLKIOLATENCY_MIN_GOOD_SAMPLES) |
568 | goto out; | |
d7067512 JB |
569 | if (lat_info->scale_grp == iolat) { |
570 | lat_info->last_scale_event = now; | |
571 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
572 | } | |
451bb7c3 JB |
573 | } else if (lat_info->scale_lat == 0 || |
574 | lat_info->scale_lat >= iolat->min_lat_nsec) { | |
d7067512 JB |
575 | lat_info->last_scale_event = now; |
576 | if (!lat_info->scale_grp || | |
577 | lat_info->scale_lat > iolat->min_lat_nsec) { | |
578 | WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec); | |
579 | lat_info->scale_grp = iolat; | |
580 | } | |
581 | scale_cookie_change(iolat->blkiolat, lat_info, false); | |
582 | } | |
451bb7c3 | 583 | latency_stat_init(iolat, &iolat->cur_stat); |
d7067512 JB |
584 | out: |
585 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
586 | } | |
587 | ||
588 | static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio) | |
589 | { | |
590 | struct blkcg_gq *blkg; | |
591 | struct rq_wait *rqw; | |
592 | struct iolatency_grp *iolat; | |
593 | u64 window_start; | |
594 | u64 now = ktime_to_ns(ktime_get()); | |
595 | bool issue_as_root = bio_issue_as_root_blkg(bio); | |
596 | bool enabled = false; | |
391f552a | 597 | int inflight = 0; |
d7067512 JB |
598 | |
599 | blkg = bio->bi_blkg; | |
13369816 | 600 | if (!blkg || !bio_flagged(bio, BIO_TRACKED)) |
d7067512 JB |
601 | return; |
602 | ||
603 | iolat = blkg_to_lat(bio->bi_blkg); | |
604 | if (!iolat) | |
605 | return; | |
606 | ||
607 | enabled = blk_iolatency_enabled(iolat->blkiolat); | |
8c772a9b LB |
608 | if (!enabled) |
609 | return; | |
610 | ||
d7067512 JB |
611 | while (blkg && blkg->parent) { |
612 | iolat = blkg_to_lat(blkg); | |
613 | if (!iolat) { | |
614 | blkg = blkg->parent; | |
615 | continue; | |
616 | } | |
617 | rqw = &iolat->rq_wait; | |
618 | ||
391f552a LB |
619 | inflight = atomic_dec_return(&rqw->inflight); |
620 | WARN_ON_ONCE(inflight < 0); | |
c9b3007f DZ |
621 | /* |
622 | * If bi_status is BLK_STS_AGAIN, the bio wasn't actually | |
623 | * submitted, so do not account for it. | |
624 | */ | |
625 | if (iolat->min_lat_nsec && bio->bi_status != BLK_STS_AGAIN) { | |
626 | iolatency_record_time(iolat, &bio->bi_issue, now, | |
627 | issue_as_root); | |
628 | window_start = atomic64_read(&iolat->window_start); | |
629 | if (now > window_start && | |
630 | (now - window_start) >= iolat->cur_win_nsec) { | |
631 | if (atomic64_cmpxchg(&iolat->window_start, | |
632 | window_start, now) == window_start) | |
633 | iolatency_check_latencies(iolat, now); | |
634 | } | |
d7067512 | 635 | } |
d7067512 | 636 | wake_up(&rqw->wait); |
d7067512 JB |
637 | blkg = blkg->parent; |
638 | } | |
639 | } | |
640 | ||
641 | static void blkcg_iolatency_exit(struct rq_qos *rqos) | |
642 | { | |
643 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
644 | ||
645 | del_timer_sync(&blkiolat->timer); | |
646 | blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency); | |
647 | kfree(blkiolat); | |
648 | } | |
649 | ||
650 | static struct rq_qos_ops blkcg_iolatency_ops = { | |
651 | .throttle = blkcg_iolatency_throttle, | |
d7067512 JB |
652 | .done_bio = blkcg_iolatency_done_bio, |
653 | .exit = blkcg_iolatency_exit, | |
654 | }; | |
655 | ||
656 | static void blkiolatency_timer_fn(struct timer_list *t) | |
657 | { | |
658 | struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer); | |
659 | struct blkcg_gq *blkg; | |
660 | struct cgroup_subsys_state *pos_css; | |
661 | u64 now = ktime_to_ns(ktime_get()); | |
662 | ||
663 | rcu_read_lock(); | |
664 | blkg_for_each_descendant_pre(blkg, pos_css, | |
665 | blkiolat->rqos.q->root_blkg) { | |
666 | struct iolatency_grp *iolat; | |
667 | struct child_latency_info *lat_info; | |
668 | unsigned long flags; | |
669 | u64 cookie; | |
670 | ||
671 | /* | |
672 | * We could be exiting, don't access the pd unless we have a | |
673 | * ref on the blkg. | |
674 | */ | |
7754f669 | 675 | if (!blkg_tryget(blkg)) |
d7067512 JB |
676 | continue; |
677 | ||
678 | iolat = blkg_to_lat(blkg); | |
679 | if (!iolat) | |
52a1199c | 680 | goto next; |
d7067512 JB |
681 | |
682 | lat_info = &iolat->child_lat; | |
683 | cookie = atomic_read(&lat_info->scale_cookie); | |
684 | ||
685 | if (cookie >= DEFAULT_SCALE_COOKIE) | |
686 | goto next; | |
687 | ||
688 | spin_lock_irqsave(&lat_info->lock, flags); | |
689 | if (lat_info->last_scale_event >= now) | |
690 | goto next_lock; | |
691 | ||
692 | /* | |
693 | * We scaled down but don't have a scale_grp, scale up and carry | |
694 | * on. | |
695 | */ | |
696 | if (lat_info->scale_grp == NULL) { | |
697 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
698 | goto next_lock; | |
699 | } | |
700 | ||
701 | /* | |
702 | * It's been 5 seconds since our last scale event, clear the | |
703 | * scale grp in case the group that needed the scale down isn't | |
704 | * doing any IO currently. | |
705 | */ | |
706 | if (now - lat_info->last_scale_event >= | |
707 | ((u64)NSEC_PER_SEC * 5)) | |
708 | lat_info->scale_grp = NULL; | |
709 | next_lock: | |
710 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
711 | next: | |
712 | blkg_put(blkg); | |
713 | } | |
714 | rcu_read_unlock(); | |
715 | } | |
716 | ||
717 | int blk_iolatency_init(struct request_queue *q) | |
718 | { | |
719 | struct blk_iolatency *blkiolat; | |
720 | struct rq_qos *rqos; | |
721 | int ret; | |
722 | ||
723 | blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL); | |
724 | if (!blkiolat) | |
725 | return -ENOMEM; | |
726 | ||
727 | rqos = &blkiolat->rqos; | |
beab17fc | 728 | rqos->id = RQ_QOS_LATENCY; |
d7067512 JB |
729 | rqos->ops = &blkcg_iolatency_ops; |
730 | rqos->q = q; | |
731 | ||
732 | rq_qos_add(q, rqos); | |
733 | ||
734 | ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); | |
735 | if (ret) { | |
736 | rq_qos_del(q, rqos); | |
737 | kfree(blkiolat); | |
738 | return ret; | |
739 | } | |
740 | ||
741 | timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); | |
742 | ||
743 | return 0; | |
744 | } | |
745 | ||
8c772a9b LB |
746 | /* |
747 | * return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise | |
748 | * return 0. | |
749 | */ | |
750 | static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) | |
d7067512 JB |
751 | { |
752 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
d7067512 JB |
753 | u64 oldval = iolat->min_lat_nsec; |
754 | ||
755 | iolat->min_lat_nsec = val; | |
c480bcf9 DZF |
756 | iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE); |
757 | iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, | |
758 | BLKIOLATENCY_MAX_WIN_SIZE); | |
d7067512 JB |
759 | |
760 | if (!oldval && val) | |
8c772a9b | 761 | return 1; |
5de0073f TH |
762 | if (oldval && !val) { |
763 | blkcg_clear_delay(blkg); | |
8c772a9b | 764 | return -1; |
5de0073f | 765 | } |
8c772a9b | 766 | return 0; |
d7067512 JB |
767 | } |
768 | ||
769 | static void iolatency_clear_scaling(struct blkcg_gq *blkg) | |
770 | { | |
771 | if (blkg->parent) { | |
772 | struct iolatency_grp *iolat = blkg_to_lat(blkg->parent); | |
773 | struct child_latency_info *lat_info; | |
774 | if (!iolat) | |
775 | return; | |
776 | ||
777 | lat_info = &iolat->child_lat; | |
778 | spin_lock(&lat_info->lock); | |
779 | atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE); | |
780 | lat_info->last_scale_event = 0; | |
781 | lat_info->scale_grp = NULL; | |
782 | lat_info->scale_lat = 0; | |
783 | spin_unlock(&lat_info->lock); | |
784 | } | |
785 | } | |
786 | ||
787 | static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, | |
788 | size_t nbytes, loff_t off) | |
789 | { | |
790 | struct blkcg *blkcg = css_to_blkcg(of_css(of)); | |
791 | struct blkcg_gq *blkg; | |
d7067512 JB |
792 | struct blkg_conf_ctx ctx; |
793 | struct iolatency_grp *iolat; | |
794 | char *p, *tok; | |
795 | u64 lat_val = 0; | |
796 | u64 oldval; | |
797 | int ret; | |
8c772a9b | 798 | int enable = 0; |
d7067512 JB |
799 | |
800 | ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); | |
801 | if (ret) | |
802 | return ret; | |
803 | ||
804 | iolat = blkg_to_lat(ctx.blkg); | |
d7067512 JB |
805 | p = ctx.body; |
806 | ||
807 | ret = -EINVAL; | |
808 | while ((tok = strsep(&p, " "))) { | |
809 | char key[16]; | |
810 | char val[21]; /* 18446744073709551616 */ | |
811 | ||
812 | if (sscanf(tok, "%15[^=]=%20s", key, val) != 2) | |
813 | goto out; | |
814 | ||
815 | if (!strcmp(key, "target")) { | |
816 | u64 v; | |
817 | ||
818 | if (!strcmp(val, "max")) | |
819 | lat_val = 0; | |
820 | else if (sscanf(val, "%llu", &v) == 1) | |
821 | lat_val = v * NSEC_PER_USEC; | |
822 | else | |
823 | goto out; | |
824 | } else { | |
825 | goto out; | |
826 | } | |
827 | } | |
828 | ||
829 | /* Walk up the tree to see if our new val is lower than it should be. */ | |
830 | blkg = ctx.blkg; | |
831 | oldval = iolat->min_lat_nsec; | |
832 | ||
8c772a9b LB |
833 | enable = iolatency_set_min_lat_nsec(blkg, lat_val); |
834 | if (enable) { | |
835 | WARN_ON_ONCE(!blk_get_queue(blkg->q)); | |
836 | blkg_get(blkg); | |
837 | } | |
838 | ||
d7067512 JB |
839 | if (oldval != iolat->min_lat_nsec) { |
840 | iolatency_clear_scaling(blkg); | |
841 | } | |
842 | ||
843 | ret = 0; | |
844 | out: | |
845 | blkg_conf_finish(&ctx); | |
8c772a9b LB |
846 | if (ret == 0 && enable) { |
847 | struct iolatency_grp *tmp = blkg_to_lat(blkg); | |
848 | struct blk_iolatency *blkiolat = tmp->blkiolat; | |
849 | ||
850 | blk_mq_freeze_queue(blkg->q); | |
851 | ||
852 | if (enable == 1) | |
853 | atomic_inc(&blkiolat->enabled); | |
854 | else if (enable == -1) | |
855 | atomic_dec(&blkiolat->enabled); | |
856 | else | |
857 | WARN_ON_ONCE(1); | |
858 | ||
859 | blk_mq_unfreeze_queue(blkg->q); | |
860 | ||
861 | blkg_put(blkg); | |
862 | blk_put_queue(blkg->q); | |
863 | } | |
d7067512 JB |
864 | return ret ?: nbytes; |
865 | } | |
866 | ||
867 | static u64 iolatency_prfill_limit(struct seq_file *sf, | |
868 | struct blkg_policy_data *pd, int off) | |
869 | { | |
870 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
871 | const char *dname = blkg_dev_name(pd->blkg); | |
872 | ||
873 | if (!dname || !iolat->min_lat_nsec) | |
874 | return 0; | |
875 | seq_printf(sf, "%s target=%llu\n", | |
88b7210c | 876 | dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC)); |
d7067512 JB |
877 | return 0; |
878 | } | |
879 | ||
880 | static int iolatency_print_limit(struct seq_file *sf, void *v) | |
881 | { | |
882 | blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), | |
883 | iolatency_prfill_limit, | |
884 | &blkcg_policy_iolatency, seq_cft(sf)->private, false); | |
885 | return 0; | |
886 | } | |
887 | ||
1fa2840e JB |
888 | static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf, |
889 | size_t size) | |
890 | { | |
891 | struct latency_stat stat; | |
892 | int cpu; | |
893 | ||
894 | latency_stat_init(iolat, &stat); | |
895 | preempt_disable(); | |
896 | for_each_online_cpu(cpu) { | |
897 | struct latency_stat *s; | |
898 | s = per_cpu_ptr(iolat->stats, cpu); | |
899 | latency_stat_sum(iolat, &stat, s); | |
900 | } | |
901 | preempt_enable(); | |
902 | ||
903 | if (iolat->rq_depth.max_depth == UINT_MAX) | |
904 | return scnprintf(buf, size, " missed=%llu total=%llu depth=max", | |
905 | (unsigned long long)stat.ps.missed, | |
906 | (unsigned long long)stat.ps.total); | |
907 | return scnprintf(buf, size, " missed=%llu total=%llu depth=%u", | |
908 | (unsigned long long)stat.ps.missed, | |
909 | (unsigned long long)stat.ps.total, | |
910 | iolat->rq_depth.max_depth); | |
911 | } | |
912 | ||
d7067512 JB |
913 | static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf, |
914 | size_t size) | |
915 | { | |
916 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1fa2840e JB |
917 | unsigned long long avg_lat; |
918 | unsigned long long cur_win; | |
919 | ||
07b0fdec TH |
920 | if (!blkcg_debug_stats) |
921 | return 0; | |
922 | ||
1fa2840e JB |
923 | if (iolat->ssd) |
924 | return iolatency_ssd_stat(iolat, buf, size); | |
d7067512 | 925 | |
1fa2840e JB |
926 | avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC); |
927 | cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC); | |
a284390b | 928 | if (iolat->rq_depth.max_depth == UINT_MAX) |
c480bcf9 DZF |
929 | return scnprintf(buf, size, " depth=max avg_lat=%llu win=%llu", |
930 | avg_lat, cur_win); | |
d7067512 | 931 | |
c480bcf9 DZF |
932 | return scnprintf(buf, size, " depth=%u avg_lat=%llu win=%llu", |
933 | iolat->rq_depth.max_depth, avg_lat, cur_win); | |
d7067512 JB |
934 | } |
935 | ||
936 | ||
cf09a8ee TH |
937 | static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, |
938 | struct request_queue *q, | |
939 | struct blkcg *blkcg) | |
d7067512 JB |
940 | { |
941 | struct iolatency_grp *iolat; | |
942 | ||
cf09a8ee | 943 | iolat = kzalloc_node(sizeof(*iolat), gfp, q->node); |
d7067512 JB |
944 | if (!iolat) |
945 | return NULL; | |
1fa2840e JB |
946 | iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat), |
947 | __alignof__(struct latency_stat), gfp); | |
d7067512 JB |
948 | if (!iolat->stats) { |
949 | kfree(iolat); | |
950 | return NULL; | |
951 | } | |
952 | return &iolat->pd; | |
953 | } | |
954 | ||
955 | static void iolatency_pd_init(struct blkg_policy_data *pd) | |
956 | { | |
957 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
958 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
959 | struct rq_qos *rqos = blkcg_rq_qos(blkg->q); | |
960 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
961 | u64 now = ktime_to_ns(ktime_get()); | |
962 | int cpu; | |
963 | ||
1fa2840e JB |
964 | if (blk_queue_nonrot(blkg->q)) |
965 | iolat->ssd = true; | |
966 | else | |
967 | iolat->ssd = false; | |
968 | ||
d7067512 | 969 | for_each_possible_cpu(cpu) { |
1fa2840e | 970 | struct latency_stat *stat; |
d7067512 | 971 | stat = per_cpu_ptr(iolat->stats, cpu); |
1fa2840e | 972 | latency_stat_init(iolat, stat); |
d7067512 JB |
973 | } |
974 | ||
451bb7c3 | 975 | latency_stat_init(iolat, &iolat->cur_stat); |
d7067512 JB |
976 | rq_wait_init(&iolat->rq_wait); |
977 | spin_lock_init(&iolat->child_lat.lock); | |
ff4cee08 | 978 | iolat->rq_depth.queue_depth = blkg->q->nr_requests; |
a284390b | 979 | iolat->rq_depth.max_depth = UINT_MAX; |
d7067512 JB |
980 | iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth; |
981 | iolat->blkiolat = blkiolat; | |
982 | iolat->cur_win_nsec = 100 * NSEC_PER_MSEC; | |
983 | atomic64_set(&iolat->window_start, now); | |
984 | ||
985 | /* | |
986 | * We init things in list order, so the pd for the parent may not be | |
987 | * init'ed yet for whatever reason. | |
988 | */ | |
989 | if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) { | |
990 | struct iolatency_grp *parent = blkg_to_lat(blkg->parent); | |
991 | atomic_set(&iolat->scale_cookie, | |
992 | atomic_read(&parent->child_lat.scale_cookie)); | |
993 | } else { | |
994 | atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE); | |
995 | } | |
996 | ||
997 | atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE); | |
998 | } | |
999 | ||
1000 | static void iolatency_pd_offline(struct blkg_policy_data *pd) | |
1001 | { | |
1002 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1003 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
8c772a9b LB |
1004 | struct blk_iolatency *blkiolat = iolat->blkiolat; |
1005 | int ret; | |
d7067512 | 1006 | |
8c772a9b LB |
1007 | ret = iolatency_set_min_lat_nsec(blkg, 0); |
1008 | if (ret == 1) | |
1009 | atomic_inc(&blkiolat->enabled); | |
1010 | if (ret == -1) | |
1011 | atomic_dec(&blkiolat->enabled); | |
d7067512 JB |
1012 | iolatency_clear_scaling(blkg); |
1013 | } | |
1014 | ||
1015 | static void iolatency_pd_free(struct blkg_policy_data *pd) | |
1016 | { | |
1017 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1018 | free_percpu(iolat->stats); | |
1019 | kfree(iolat); | |
1020 | } | |
1021 | ||
1022 | static struct cftype iolatency_files[] = { | |
1023 | { | |
1024 | .name = "latency", | |
1025 | .flags = CFTYPE_NOT_ON_ROOT, | |
1026 | .seq_show = iolatency_print_limit, | |
1027 | .write = iolatency_set_limit, | |
1028 | }, | |
1029 | {} | |
1030 | }; | |
1031 | ||
1032 | static struct blkcg_policy blkcg_policy_iolatency = { | |
1033 | .dfl_cftypes = iolatency_files, | |
1034 | .pd_alloc_fn = iolatency_pd_alloc, | |
1035 | .pd_init_fn = iolatency_pd_init, | |
1036 | .pd_offline_fn = iolatency_pd_offline, | |
1037 | .pd_free_fn = iolatency_pd_free, | |
1038 | .pd_stat_fn = iolatency_pd_stat, | |
1039 | }; | |
1040 | ||
1041 | static int __init iolatency_init(void) | |
1042 | { | |
1043 | return blkcg_policy_register(&blkcg_policy_iolatency); | |
1044 | } | |
1045 | ||
1046 | static void __exit iolatency_exit(void) | |
1047 | { | |
1048 | return blkcg_policy_unregister(&blkcg_policy_iolatency); | |
1049 | } | |
1050 | ||
1051 | module_init(iolatency_init); | |
1052 | module_exit(iolatency_exit); |