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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. | |
a284390b JB |
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 | |
d7067512 JB |
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> | |
c480bcf9 | 72 | #include <linux/sched/loadavg.h> |
d7067512 JB |
73 | #include <linux/sched/signal.h> |
74 | #include <trace/events/block.h> | |
8c772a9b | 75 | #include <linux/blk-mq.h> |
d7067512 JB |
76 | #include "blk-rq-qos.h" |
77 | #include "blk-stat.h" | |
78 | ||
79 | #define DEFAULT_SCALE_COOKIE 1000000U | |
80 | ||
81 | static struct blkcg_policy blkcg_policy_iolatency; | |
82 | struct iolatency_grp; | |
83 | ||
84 | struct blk_iolatency { | |
85 | struct rq_qos rqos; | |
86 | struct timer_list timer; | |
87 | atomic_t enabled; | |
88 | }; | |
89 | ||
90 | static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) | |
91 | { | |
92 | return container_of(rqos, struct blk_iolatency, rqos); | |
93 | } | |
94 | ||
95 | static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat) | |
96 | { | |
97 | return atomic_read(&blkiolat->enabled) > 0; | |
98 | } | |
99 | ||
100 | struct child_latency_info { | |
101 | spinlock_t lock; | |
102 | ||
103 | /* Last time we adjusted the scale of everybody. */ | |
104 | u64 last_scale_event; | |
105 | ||
106 | /* The latency that we missed. */ | |
107 | u64 scale_lat; | |
108 | ||
109 | /* Total io's from all of our children for the last summation. */ | |
110 | u64 nr_samples; | |
111 | ||
112 | /* The guy who actually changed the latency numbers. */ | |
113 | struct iolatency_grp *scale_grp; | |
114 | ||
115 | /* Cookie to tell if we need to scale up or down. */ | |
116 | atomic_t scale_cookie; | |
117 | }; | |
118 | ||
1fa2840e JB |
119 | struct percentile_stats { |
120 | u64 total; | |
121 | u64 missed; | |
122 | }; | |
123 | ||
124 | struct latency_stat { | |
125 | union { | |
126 | struct percentile_stats ps; | |
127 | struct blk_rq_stat rqs; | |
128 | }; | |
129 | }; | |
130 | ||
d7067512 JB |
131 | struct iolatency_grp { |
132 | struct blkg_policy_data pd; | |
1fa2840e | 133 | struct latency_stat __percpu *stats; |
451bb7c3 | 134 | struct latency_stat cur_stat; |
d7067512 JB |
135 | struct blk_iolatency *blkiolat; |
136 | struct rq_depth rq_depth; | |
137 | struct rq_wait rq_wait; | |
138 | atomic64_t window_start; | |
139 | atomic_t scale_cookie; | |
140 | u64 min_lat_nsec; | |
141 | u64 cur_win_nsec; | |
142 | ||
143 | /* total running average of our io latency. */ | |
c480bcf9 | 144 | u64 lat_avg; |
d7067512 JB |
145 | |
146 | /* Our current number of IO's for the last summation. */ | |
147 | u64 nr_samples; | |
148 | ||
1fa2840e | 149 | bool ssd; |
d7067512 JB |
150 | struct child_latency_info child_lat; |
151 | }; | |
152 | ||
c480bcf9 DZF |
153 | #define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC) |
154 | #define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC | |
155 | /* | |
156 | * These are the constants used to fake the fixed-point moving average | |
8508cf3f | 157 | * calculation just like load average. The call to calc_load() folds |
c480bcf9 DZF |
158 | * (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling |
159 | * window size is bucketed to try to approximately calculate average | |
160 | * latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows | |
161 | * elapse immediately. Note, windows only elapse with IO activity. Idle | |
162 | * periods extend the most recent window. | |
163 | */ | |
164 | #define BLKIOLATENCY_NR_EXP_FACTORS 5 | |
165 | #define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \ | |
166 | (BLKIOLATENCY_NR_EXP_FACTORS - 1)) | |
167 | static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = { | |
168 | 2045, // exp(1/600) - 600 samples | |
169 | 2039, // exp(1/240) - 240 samples | |
170 | 2031, // exp(1/120) - 120 samples | |
171 | 2023, // exp(1/80) - 80 samples | |
172 | 2014, // exp(1/60) - 60 samples | |
173 | }; | |
174 | ||
d7067512 JB |
175 | static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd) |
176 | { | |
177 | return pd ? container_of(pd, struct iolatency_grp, pd) : NULL; | |
178 | } | |
179 | ||
180 | static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg) | |
181 | { | |
182 | return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency)); | |
183 | } | |
184 | ||
185 | static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat) | |
186 | { | |
187 | return pd_to_blkg(&iolat->pd); | |
188 | } | |
189 | ||
1fa2840e JB |
190 | static inline void latency_stat_init(struct iolatency_grp *iolat, |
191 | struct latency_stat *stat) | |
192 | { | |
193 | if (iolat->ssd) { | |
194 | stat->ps.total = 0; | |
195 | stat->ps.missed = 0; | |
196 | } else | |
197 | blk_rq_stat_init(&stat->rqs); | |
198 | } | |
199 | ||
200 | static inline void latency_stat_sum(struct iolatency_grp *iolat, | |
201 | struct latency_stat *sum, | |
202 | struct latency_stat *stat) | |
203 | { | |
204 | if (iolat->ssd) { | |
205 | sum->ps.total += stat->ps.total; | |
206 | sum->ps.missed += stat->ps.missed; | |
207 | } else | |
208 | blk_rq_stat_sum(&sum->rqs, &stat->rqs); | |
209 | } | |
210 | ||
211 | static inline void latency_stat_record_time(struct iolatency_grp *iolat, | |
212 | u64 req_time) | |
213 | { | |
214 | struct latency_stat *stat = get_cpu_ptr(iolat->stats); | |
215 | if (iolat->ssd) { | |
216 | if (req_time >= iolat->min_lat_nsec) | |
217 | stat->ps.missed++; | |
218 | stat->ps.total++; | |
219 | } else | |
220 | blk_rq_stat_add(&stat->rqs, req_time); | |
221 | put_cpu_ptr(stat); | |
222 | } | |
223 | ||
224 | static inline bool latency_sum_ok(struct iolatency_grp *iolat, | |
225 | struct latency_stat *stat) | |
226 | { | |
227 | if (iolat->ssd) { | |
228 | u64 thresh = div64_u64(stat->ps.total, 10); | |
229 | thresh = max(thresh, 1ULL); | |
230 | return stat->ps.missed < thresh; | |
231 | } | |
232 | return stat->rqs.mean <= iolat->min_lat_nsec; | |
233 | } | |
234 | ||
235 | static inline u64 latency_stat_samples(struct iolatency_grp *iolat, | |
236 | struct latency_stat *stat) | |
237 | { | |
238 | if (iolat->ssd) | |
239 | return stat->ps.total; | |
240 | return stat->rqs.nr_samples; | |
241 | } | |
242 | ||
243 | static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat, | |
244 | struct latency_stat *stat) | |
245 | { | |
246 | int exp_idx; | |
247 | ||
248 | if (iolat->ssd) | |
249 | return; | |
250 | ||
251 | /* | |
8508cf3f | 252 | * calc_load() takes in a number stored in fixed point representation. |
1fa2840e JB |
253 | * Because we are using this for IO time in ns, the values stored |
254 | * are significantly larger than the FIXED_1 denominator (2048). | |
255 | * Therefore, rounding errors in the calculation are negligible and | |
256 | * can be ignored. | |
257 | */ | |
258 | exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1, | |
259 | div64_u64(iolat->cur_win_nsec, | |
260 | BLKIOLATENCY_EXP_BUCKET_SIZE)); | |
8508cf3f JW |
261 | iolat->lat_avg = calc_load(iolat->lat_avg, |
262 | iolatency_exp_factors[exp_idx], | |
263 | stat->rqs.mean); | |
1fa2840e JB |
264 | } |
265 | ||
d3fcdff1 | 266 | static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data) |
d7067512 | 267 | { |
d3fcdff1 JB |
268 | atomic_dec(&rqw->inflight); |
269 | wake_up(&rqw->wait); | |
270 | } | |
d7067512 | 271 | |
d3fcdff1 JB |
272 | static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data) |
273 | { | |
274 | struct iolatency_grp *iolat = private_data; | |
d7067512 JB |
275 | return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth); |
276 | } | |
277 | ||
278 | static void __blkcg_iolatency_throttle(struct rq_qos *rqos, | |
279 | struct iolatency_grp *iolat, | |
d5337560 | 280 | bool issue_as_root, |
d7067512 | 281 | bool use_memdelay) |
d7067512 JB |
282 | { |
283 | struct rq_wait *rqw = &iolat->rq_wait; | |
284 | unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay); | |
d7067512 JB |
285 | |
286 | if (use_delay) | |
287 | blkcg_schedule_throttle(rqos->q, use_memdelay); | |
288 | ||
289 | /* | |
290 | * To avoid priority inversions we want to just take a slot if we are | |
291 | * issuing as root. If we're being killed off there's no point in | |
292 | * delaying things, we may have been killed by OOM so throttling may | |
293 | * make recovery take even longer, so just let the IO's through so the | |
294 | * task can go away. | |
295 | */ | |
296 | if (issue_as_root || fatal_signal_pending(current)) { | |
297 | atomic_inc(&rqw->inflight); | |
298 | return; | |
299 | } | |
300 | ||
d3fcdff1 | 301 | rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb); |
d7067512 JB |
302 | } |
303 | ||
304 | #define SCALE_DOWN_FACTOR 2 | |
305 | #define SCALE_UP_FACTOR 4 | |
306 | ||
307 | static inline unsigned long scale_amount(unsigned long qd, bool up) | |
308 | { | |
309 | return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL); | |
310 | } | |
311 | ||
312 | /* | |
313 | * We scale the qd down faster than we scale up, so we need to use this helper | |
314 | * to adjust the scale_cookie accordingly so we don't prematurely get | |
315 | * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much. | |
316 | * | |
317 | * Each group has their own local copy of the last scale cookie they saw, so if | |
318 | * the global scale cookie goes up or down they know which way they need to go | |
319 | * based on their last knowledge of it. | |
320 | */ | |
321 | static void scale_cookie_change(struct blk_iolatency *blkiolat, | |
322 | struct child_latency_info *lat_info, | |
323 | bool up) | |
324 | { | |
ff4cee08 | 325 | unsigned long qd = blkiolat->rqos.q->nr_requests; |
d7067512 JB |
326 | unsigned long scale = scale_amount(qd, up); |
327 | unsigned long old = atomic_read(&lat_info->scale_cookie); | |
328 | unsigned long max_scale = qd << 1; | |
329 | unsigned long diff = 0; | |
330 | ||
331 | if (old < DEFAULT_SCALE_COOKIE) | |
332 | diff = DEFAULT_SCALE_COOKIE - old; | |
333 | ||
334 | if (up) { | |
335 | if (scale + old > DEFAULT_SCALE_COOKIE) | |
336 | atomic_set(&lat_info->scale_cookie, | |
337 | DEFAULT_SCALE_COOKIE); | |
338 | else if (diff > qd) | |
339 | atomic_inc(&lat_info->scale_cookie); | |
340 | else | |
341 | atomic_add(scale, &lat_info->scale_cookie); | |
342 | } else { | |
343 | /* | |
344 | * We don't want to dig a hole so deep that it takes us hours to | |
345 | * dig out of it. Just enough that we don't throttle/unthrottle | |
346 | * with jagged workloads but can still unthrottle once pressure | |
347 | * has sufficiently dissipated. | |
348 | */ | |
349 | if (diff > qd) { | |
350 | if (diff < max_scale) | |
351 | atomic_dec(&lat_info->scale_cookie); | |
352 | } else { | |
353 | atomic_sub(scale, &lat_info->scale_cookie); | |
354 | } | |
355 | } | |
356 | } | |
357 | ||
358 | /* | |
359 | * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the | |
360 | * queue depth at a time so we don't get wild swings and hopefully dial in to | |
361 | * fairer distribution of the overall queue depth. | |
362 | */ | |
363 | static void scale_change(struct iolatency_grp *iolat, bool up) | |
364 | { | |
ff4cee08 | 365 | unsigned long qd = iolat->blkiolat->rqos.q->nr_requests; |
d7067512 JB |
366 | unsigned long scale = scale_amount(qd, up); |
367 | unsigned long old = iolat->rq_depth.max_depth; | |
d7067512 JB |
368 | |
369 | if (old > qd) | |
370 | old = qd; | |
371 | ||
372 | if (up) { | |
373 | if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat))) | |
374 | return; | |
375 | ||
376 | if (old < qd) { | |
d7067512 JB |
377 | old += scale; |
378 | old = min(old, qd); | |
379 | iolat->rq_depth.max_depth = old; | |
380 | wake_up_all(&iolat->rq_wait.wait); | |
381 | } | |
9f60511a | 382 | } else { |
d7067512 | 383 | old >>= 1; |
d7067512 JB |
384 | iolat->rq_depth.max_depth = max(old, 1UL); |
385 | } | |
386 | } | |
387 | ||
388 | /* Check our parent and see if the scale cookie has changed. */ | |
389 | static void check_scale_change(struct iolatency_grp *iolat) | |
390 | { | |
391 | struct iolatency_grp *parent; | |
392 | struct child_latency_info *lat_info; | |
393 | unsigned int cur_cookie; | |
394 | unsigned int our_cookie = atomic_read(&iolat->scale_cookie); | |
395 | u64 scale_lat; | |
396 | unsigned int old; | |
397 | int direction = 0; | |
398 | ||
399 | if (lat_to_blkg(iolat)->parent == NULL) | |
400 | return; | |
401 | ||
402 | parent = blkg_to_lat(lat_to_blkg(iolat)->parent); | |
403 | if (!parent) | |
404 | return; | |
405 | ||
406 | lat_info = &parent->child_lat; | |
407 | cur_cookie = atomic_read(&lat_info->scale_cookie); | |
408 | scale_lat = READ_ONCE(lat_info->scale_lat); | |
409 | ||
410 | if (cur_cookie < our_cookie) | |
411 | direction = -1; | |
412 | else if (cur_cookie > our_cookie) | |
413 | direction = 1; | |
414 | else | |
415 | return; | |
416 | ||
417 | old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie); | |
418 | ||
419 | /* Somebody beat us to the punch, just bail. */ | |
420 | if (old != our_cookie) | |
421 | return; | |
422 | ||
423 | if (direction < 0 && iolat->min_lat_nsec) { | |
424 | u64 samples_thresh; | |
425 | ||
426 | if (!scale_lat || iolat->min_lat_nsec <= scale_lat) | |
427 | return; | |
428 | ||
429 | /* | |
430 | * Sometimes high priority groups are their own worst enemy, so | |
431 | * instead of taking it out on some poor other group that did 5% | |
432 | * or less of the IO's for the last summation just skip this | |
433 | * scale down event. | |
434 | */ | |
435 | samples_thresh = lat_info->nr_samples * 5; | |
22ed8a93 | 436 | samples_thresh = max(1ULL, div64_u64(samples_thresh, 100)); |
d7067512 JB |
437 | if (iolat->nr_samples <= samples_thresh) |
438 | return; | |
439 | } | |
440 | ||
441 | /* We're as low as we can go. */ | |
442 | if (iolat->rq_depth.max_depth == 1 && direction < 0) { | |
443 | blkcg_use_delay(lat_to_blkg(iolat)); | |
444 | return; | |
445 | } | |
446 | ||
447 | /* We're back to the default cookie, unthrottle all the things. */ | |
448 | if (cur_cookie == DEFAULT_SCALE_COOKIE) { | |
449 | blkcg_clear_delay(lat_to_blkg(iolat)); | |
a284390b | 450 | iolat->rq_depth.max_depth = UINT_MAX; |
d7067512 JB |
451 | wake_up_all(&iolat->rq_wait.wait); |
452 | return; | |
453 | } | |
454 | ||
455 | scale_change(iolat, direction > 0); | |
456 | } | |
457 | ||
d5337560 | 458 | static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio) |
d7067512 JB |
459 | { |
460 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
5cdf2e3f | 461 | struct blkcg_gq *blkg = bio->bi_blkg; |
d7067512 JB |
462 | bool issue_as_root = bio_issue_as_root_blkg(bio); |
463 | ||
464 | if (!blk_iolatency_enabled(blkiolat)) | |
465 | return; | |
466 | ||
d7067512 JB |
467 | while (blkg && blkg->parent) { |
468 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
469 | if (!iolat) { | |
470 | blkg = blkg->parent; | |
471 | continue; | |
472 | } | |
473 | ||
474 | check_scale_change(iolat); | |
d5337560 | 475 | __blkcg_iolatency_throttle(rqos, iolat, issue_as_root, |
d7067512 JB |
476 | (bio->bi_opf & REQ_SWAP) == REQ_SWAP); |
477 | blkg = blkg->parent; | |
478 | } | |
479 | if (!timer_pending(&blkiolat->timer)) | |
480 | mod_timer(&blkiolat->timer, jiffies + HZ); | |
481 | } | |
482 | ||
483 | static void iolatency_record_time(struct iolatency_grp *iolat, | |
484 | struct bio_issue *issue, u64 now, | |
485 | bool issue_as_root) | |
486 | { | |
d7067512 JB |
487 | u64 start = bio_issue_time(issue); |
488 | u64 req_time; | |
489 | ||
71e9690b JB |
490 | /* |
491 | * Have to do this so we are truncated to the correct time that our | |
492 | * issue is truncated to. | |
493 | */ | |
494 | now = __bio_issue_time(now); | |
495 | ||
d7067512 JB |
496 | if (now <= start) |
497 | return; | |
498 | ||
499 | req_time = now - start; | |
500 | ||
501 | /* | |
502 | * We don't want to count issue_as_root bio's in the cgroups latency | |
503 | * statistics as it could skew the numbers downwards. | |
504 | */ | |
a284390b | 505 | if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) { |
d7067512 JB |
506 | u64 sub = iolat->min_lat_nsec; |
507 | if (req_time < sub) | |
508 | blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time); | |
509 | return; | |
510 | } | |
511 | ||
1fa2840e | 512 | latency_stat_record_time(iolat, req_time); |
d7067512 JB |
513 | } |
514 | ||
515 | #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC) | |
516 | #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5 | |
517 | ||
518 | static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) | |
519 | { | |
520 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
521 | struct iolatency_grp *parent; | |
522 | struct child_latency_info *lat_info; | |
1fa2840e | 523 | struct latency_stat stat; |
d7067512 | 524 | unsigned long flags; |
1fa2840e | 525 | int cpu; |
d7067512 | 526 | |
1fa2840e | 527 | latency_stat_init(iolat, &stat); |
d7067512 JB |
528 | preempt_disable(); |
529 | for_each_online_cpu(cpu) { | |
1fa2840e | 530 | struct latency_stat *s; |
d7067512 | 531 | s = per_cpu_ptr(iolat->stats, cpu); |
1fa2840e JB |
532 | latency_stat_sum(iolat, &stat, s); |
533 | latency_stat_init(iolat, s); | |
d7067512 JB |
534 | } |
535 | preempt_enable(); | |
536 | ||
d7067512 JB |
537 | parent = blkg_to_lat(blkg->parent); |
538 | if (!parent) | |
539 | return; | |
540 | ||
541 | lat_info = &parent->child_lat; | |
542 | ||
1fa2840e | 543 | iolat_update_total_lat_avg(iolat, &stat); |
d7067512 JB |
544 | |
545 | /* Everything is ok and we don't need to adjust the scale. */ | |
1fa2840e | 546 | if (latency_sum_ok(iolat, &stat) && |
d7067512 JB |
547 | atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE) |
548 | return; | |
549 | ||
550 | /* Somebody beat us to the punch, just bail. */ | |
551 | spin_lock_irqsave(&lat_info->lock, flags); | |
451bb7c3 JB |
552 | |
553 | latency_stat_sum(iolat, &iolat->cur_stat, &stat); | |
d7067512 | 554 | lat_info->nr_samples -= iolat->nr_samples; |
451bb7c3 JB |
555 | lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat); |
556 | iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat); | |
d7067512 JB |
557 | |
558 | if ((lat_info->last_scale_event >= now || | |
451bb7c3 | 559 | now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME)) |
d7067512 JB |
560 | goto out; |
561 | ||
451bb7c3 JB |
562 | if (latency_sum_ok(iolat, &iolat->cur_stat) && |
563 | latency_sum_ok(iolat, &stat)) { | |
564 | if (latency_stat_samples(iolat, &iolat->cur_stat) < | |
1fa2840e JB |
565 | BLKIOLATENCY_MIN_GOOD_SAMPLES) |
566 | goto out; | |
d7067512 JB |
567 | if (lat_info->scale_grp == iolat) { |
568 | lat_info->last_scale_event = now; | |
569 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
570 | } | |
451bb7c3 JB |
571 | } else if (lat_info->scale_lat == 0 || |
572 | lat_info->scale_lat >= iolat->min_lat_nsec) { | |
d7067512 JB |
573 | lat_info->last_scale_event = now; |
574 | if (!lat_info->scale_grp || | |
575 | lat_info->scale_lat > iolat->min_lat_nsec) { | |
576 | WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec); | |
577 | lat_info->scale_grp = iolat; | |
578 | } | |
579 | scale_cookie_change(iolat->blkiolat, lat_info, false); | |
580 | } | |
451bb7c3 | 581 | latency_stat_init(iolat, &iolat->cur_stat); |
d7067512 JB |
582 | out: |
583 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
584 | } | |
585 | ||
586 | static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio) | |
587 | { | |
588 | struct blkcg_gq *blkg; | |
589 | struct rq_wait *rqw; | |
590 | struct iolatency_grp *iolat; | |
591 | u64 window_start; | |
592 | u64 now = ktime_to_ns(ktime_get()); | |
593 | bool issue_as_root = bio_issue_as_root_blkg(bio); | |
594 | bool enabled = false; | |
391f552a | 595 | int inflight = 0; |
d7067512 JB |
596 | |
597 | blkg = bio->bi_blkg; | |
13369816 | 598 | if (!blkg || !bio_flagged(bio, BIO_TRACKED)) |
d7067512 JB |
599 | return; |
600 | ||
601 | iolat = blkg_to_lat(bio->bi_blkg); | |
602 | if (!iolat) | |
603 | return; | |
604 | ||
605 | enabled = blk_iolatency_enabled(iolat->blkiolat); | |
8c772a9b LB |
606 | if (!enabled) |
607 | return; | |
608 | ||
d7067512 JB |
609 | while (blkg && blkg->parent) { |
610 | iolat = blkg_to_lat(blkg); | |
611 | if (!iolat) { | |
612 | blkg = blkg->parent; | |
613 | continue; | |
614 | } | |
615 | rqw = &iolat->rq_wait; | |
616 | ||
391f552a LB |
617 | inflight = atomic_dec_return(&rqw->inflight); |
618 | WARN_ON_ONCE(inflight < 0); | |
8c772a9b | 619 | if (iolat->min_lat_nsec == 0) |
d7067512 JB |
620 | goto next; |
621 | iolatency_record_time(iolat, &bio->bi_issue, now, | |
622 | issue_as_root); | |
623 | window_start = atomic64_read(&iolat->window_start); | |
624 | if (now > window_start && | |
625 | (now - window_start) >= iolat->cur_win_nsec) { | |
626 | if (atomic64_cmpxchg(&iolat->window_start, | |
627 | window_start, now) == window_start) | |
628 | iolatency_check_latencies(iolat, now); | |
629 | } | |
630 | next: | |
631 | wake_up(&rqw->wait); | |
632 | blkg = blkg->parent; | |
633 | } | |
634 | } | |
635 | ||
636 | static void blkcg_iolatency_cleanup(struct rq_qos *rqos, struct bio *bio) | |
637 | { | |
638 | struct blkcg_gq *blkg; | |
639 | ||
640 | blkg = bio->bi_blkg; | |
641 | while (blkg && blkg->parent) { | |
642 | struct rq_wait *rqw; | |
643 | struct iolatency_grp *iolat; | |
644 | ||
645 | iolat = blkg_to_lat(blkg); | |
646 | if (!iolat) | |
647 | goto next; | |
648 | ||
649 | rqw = &iolat->rq_wait; | |
650 | atomic_dec(&rqw->inflight); | |
651 | wake_up(&rqw->wait); | |
652 | next: | |
653 | blkg = blkg->parent; | |
654 | } | |
655 | } | |
656 | ||
657 | static void blkcg_iolatency_exit(struct rq_qos *rqos) | |
658 | { | |
659 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
660 | ||
661 | del_timer_sync(&blkiolat->timer); | |
662 | blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency); | |
663 | kfree(blkiolat); | |
664 | } | |
665 | ||
666 | static struct rq_qos_ops blkcg_iolatency_ops = { | |
667 | .throttle = blkcg_iolatency_throttle, | |
668 | .cleanup = blkcg_iolatency_cleanup, | |
669 | .done_bio = blkcg_iolatency_done_bio, | |
670 | .exit = blkcg_iolatency_exit, | |
671 | }; | |
672 | ||
673 | static void blkiolatency_timer_fn(struct timer_list *t) | |
674 | { | |
675 | struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer); | |
676 | struct blkcg_gq *blkg; | |
677 | struct cgroup_subsys_state *pos_css; | |
678 | u64 now = ktime_to_ns(ktime_get()); | |
679 | ||
680 | rcu_read_lock(); | |
681 | blkg_for_each_descendant_pre(blkg, pos_css, | |
682 | blkiolat->rqos.q->root_blkg) { | |
683 | struct iolatency_grp *iolat; | |
684 | struct child_latency_info *lat_info; | |
685 | unsigned long flags; | |
686 | u64 cookie; | |
687 | ||
688 | /* | |
689 | * We could be exiting, don't access the pd unless we have a | |
690 | * ref on the blkg. | |
691 | */ | |
7754f669 | 692 | if (!blkg_tryget(blkg)) |
d7067512 JB |
693 | continue; |
694 | ||
695 | iolat = blkg_to_lat(blkg); | |
696 | if (!iolat) | |
52a1199c | 697 | goto next; |
d7067512 JB |
698 | |
699 | lat_info = &iolat->child_lat; | |
700 | cookie = atomic_read(&lat_info->scale_cookie); | |
701 | ||
702 | if (cookie >= DEFAULT_SCALE_COOKIE) | |
703 | goto next; | |
704 | ||
705 | spin_lock_irqsave(&lat_info->lock, flags); | |
706 | if (lat_info->last_scale_event >= now) | |
707 | goto next_lock; | |
708 | ||
709 | /* | |
710 | * We scaled down but don't have a scale_grp, scale up and carry | |
711 | * on. | |
712 | */ | |
713 | if (lat_info->scale_grp == NULL) { | |
714 | scale_cookie_change(iolat->blkiolat, lat_info, true); | |
715 | goto next_lock; | |
716 | } | |
717 | ||
718 | /* | |
719 | * It's been 5 seconds since our last scale event, clear the | |
720 | * scale grp in case the group that needed the scale down isn't | |
721 | * doing any IO currently. | |
722 | */ | |
723 | if (now - lat_info->last_scale_event >= | |
724 | ((u64)NSEC_PER_SEC * 5)) | |
725 | lat_info->scale_grp = NULL; | |
726 | next_lock: | |
727 | spin_unlock_irqrestore(&lat_info->lock, flags); | |
728 | next: | |
729 | blkg_put(blkg); | |
730 | } | |
731 | rcu_read_unlock(); | |
732 | } | |
733 | ||
734 | int blk_iolatency_init(struct request_queue *q) | |
735 | { | |
736 | struct blk_iolatency *blkiolat; | |
737 | struct rq_qos *rqos; | |
738 | int ret; | |
739 | ||
740 | blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL); | |
741 | if (!blkiolat) | |
742 | return -ENOMEM; | |
743 | ||
744 | rqos = &blkiolat->rqos; | |
745 | rqos->id = RQ_QOS_CGROUP; | |
746 | rqos->ops = &blkcg_iolatency_ops; | |
747 | rqos->q = q; | |
748 | ||
749 | rq_qos_add(q, rqos); | |
750 | ||
751 | ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); | |
752 | if (ret) { | |
753 | rq_qos_del(q, rqos); | |
754 | kfree(blkiolat); | |
755 | return ret; | |
756 | } | |
757 | ||
758 | timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); | |
759 | ||
760 | return 0; | |
761 | } | |
762 | ||
8c772a9b LB |
763 | /* |
764 | * return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise | |
765 | * return 0. | |
766 | */ | |
767 | static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) | |
d7067512 JB |
768 | { |
769 | struct iolatency_grp *iolat = blkg_to_lat(blkg); | |
d7067512 JB |
770 | u64 oldval = iolat->min_lat_nsec; |
771 | ||
772 | iolat->min_lat_nsec = val; | |
c480bcf9 DZF |
773 | iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE); |
774 | iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, | |
775 | BLKIOLATENCY_MAX_WIN_SIZE); | |
d7067512 JB |
776 | |
777 | if (!oldval && val) | |
8c772a9b | 778 | return 1; |
d7067512 | 779 | if (oldval && !val) |
8c772a9b LB |
780 | return -1; |
781 | return 0; | |
d7067512 JB |
782 | } |
783 | ||
784 | static void iolatency_clear_scaling(struct blkcg_gq *blkg) | |
785 | { | |
786 | if (blkg->parent) { | |
787 | struct iolatency_grp *iolat = blkg_to_lat(blkg->parent); | |
788 | struct child_latency_info *lat_info; | |
789 | if (!iolat) | |
790 | return; | |
791 | ||
792 | lat_info = &iolat->child_lat; | |
793 | spin_lock(&lat_info->lock); | |
794 | atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE); | |
795 | lat_info->last_scale_event = 0; | |
796 | lat_info->scale_grp = NULL; | |
797 | lat_info->scale_lat = 0; | |
798 | spin_unlock(&lat_info->lock); | |
799 | } | |
800 | } | |
801 | ||
802 | static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, | |
803 | size_t nbytes, loff_t off) | |
804 | { | |
805 | struct blkcg *blkcg = css_to_blkcg(of_css(of)); | |
806 | struct blkcg_gq *blkg; | |
d7067512 JB |
807 | struct blkg_conf_ctx ctx; |
808 | struct iolatency_grp *iolat; | |
809 | char *p, *tok; | |
810 | u64 lat_val = 0; | |
811 | u64 oldval; | |
812 | int ret; | |
8c772a9b | 813 | int enable = 0; |
d7067512 JB |
814 | |
815 | ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); | |
816 | if (ret) | |
817 | return ret; | |
818 | ||
819 | iolat = blkg_to_lat(ctx.blkg); | |
d7067512 JB |
820 | p = ctx.body; |
821 | ||
822 | ret = -EINVAL; | |
823 | while ((tok = strsep(&p, " "))) { | |
824 | char key[16]; | |
825 | char val[21]; /* 18446744073709551616 */ | |
826 | ||
827 | if (sscanf(tok, "%15[^=]=%20s", key, val) != 2) | |
828 | goto out; | |
829 | ||
830 | if (!strcmp(key, "target")) { | |
831 | u64 v; | |
832 | ||
833 | if (!strcmp(val, "max")) | |
834 | lat_val = 0; | |
835 | else if (sscanf(val, "%llu", &v) == 1) | |
836 | lat_val = v * NSEC_PER_USEC; | |
837 | else | |
838 | goto out; | |
839 | } else { | |
840 | goto out; | |
841 | } | |
842 | } | |
843 | ||
844 | /* Walk up the tree to see if our new val is lower than it should be. */ | |
845 | blkg = ctx.blkg; | |
846 | oldval = iolat->min_lat_nsec; | |
847 | ||
8c772a9b LB |
848 | enable = iolatency_set_min_lat_nsec(blkg, lat_val); |
849 | if (enable) { | |
850 | WARN_ON_ONCE(!blk_get_queue(blkg->q)); | |
851 | blkg_get(blkg); | |
852 | } | |
853 | ||
d7067512 JB |
854 | if (oldval != iolat->min_lat_nsec) { |
855 | iolatency_clear_scaling(blkg); | |
856 | } | |
857 | ||
858 | ret = 0; | |
859 | out: | |
860 | blkg_conf_finish(&ctx); | |
8c772a9b LB |
861 | if (ret == 0 && enable) { |
862 | struct iolatency_grp *tmp = blkg_to_lat(blkg); | |
863 | struct blk_iolatency *blkiolat = tmp->blkiolat; | |
864 | ||
865 | blk_mq_freeze_queue(blkg->q); | |
866 | ||
867 | if (enable == 1) | |
868 | atomic_inc(&blkiolat->enabled); | |
869 | else if (enable == -1) | |
870 | atomic_dec(&blkiolat->enabled); | |
871 | else | |
872 | WARN_ON_ONCE(1); | |
873 | ||
874 | blk_mq_unfreeze_queue(blkg->q); | |
875 | ||
876 | blkg_put(blkg); | |
877 | blk_put_queue(blkg->q); | |
878 | } | |
d7067512 JB |
879 | return ret ?: nbytes; |
880 | } | |
881 | ||
882 | static u64 iolatency_prfill_limit(struct seq_file *sf, | |
883 | struct blkg_policy_data *pd, int off) | |
884 | { | |
885 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
886 | const char *dname = blkg_dev_name(pd->blkg); | |
887 | ||
888 | if (!dname || !iolat->min_lat_nsec) | |
889 | return 0; | |
890 | seq_printf(sf, "%s target=%llu\n", | |
88b7210c | 891 | dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC)); |
d7067512 JB |
892 | return 0; |
893 | } | |
894 | ||
895 | static int iolatency_print_limit(struct seq_file *sf, void *v) | |
896 | { | |
897 | blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), | |
898 | iolatency_prfill_limit, | |
899 | &blkcg_policy_iolatency, seq_cft(sf)->private, false); | |
900 | return 0; | |
901 | } | |
902 | ||
1fa2840e JB |
903 | static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf, |
904 | size_t size) | |
905 | { | |
906 | struct latency_stat stat; | |
907 | int cpu; | |
908 | ||
909 | latency_stat_init(iolat, &stat); | |
910 | preempt_disable(); | |
911 | for_each_online_cpu(cpu) { | |
912 | struct latency_stat *s; | |
913 | s = per_cpu_ptr(iolat->stats, cpu); | |
914 | latency_stat_sum(iolat, &stat, s); | |
915 | } | |
916 | preempt_enable(); | |
917 | ||
918 | if (iolat->rq_depth.max_depth == UINT_MAX) | |
919 | return scnprintf(buf, size, " missed=%llu total=%llu depth=max", | |
920 | (unsigned long long)stat.ps.missed, | |
921 | (unsigned long long)stat.ps.total); | |
922 | return scnprintf(buf, size, " missed=%llu total=%llu depth=%u", | |
923 | (unsigned long long)stat.ps.missed, | |
924 | (unsigned long long)stat.ps.total, | |
925 | iolat->rq_depth.max_depth); | |
926 | } | |
927 | ||
d7067512 JB |
928 | static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf, |
929 | size_t size) | |
930 | { | |
931 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1fa2840e JB |
932 | unsigned long long avg_lat; |
933 | unsigned long long cur_win; | |
934 | ||
935 | if (iolat->ssd) | |
936 | return iolatency_ssd_stat(iolat, buf, size); | |
d7067512 | 937 | |
1fa2840e JB |
938 | avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC); |
939 | cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC); | |
a284390b | 940 | if (iolat->rq_depth.max_depth == UINT_MAX) |
c480bcf9 DZF |
941 | return scnprintf(buf, size, " depth=max avg_lat=%llu win=%llu", |
942 | avg_lat, cur_win); | |
d7067512 | 943 | |
c480bcf9 DZF |
944 | return scnprintf(buf, size, " depth=%u avg_lat=%llu win=%llu", |
945 | iolat->rq_depth.max_depth, avg_lat, cur_win); | |
d7067512 JB |
946 | } |
947 | ||
948 | ||
949 | static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, int node) | |
950 | { | |
951 | struct iolatency_grp *iolat; | |
952 | ||
953 | iolat = kzalloc_node(sizeof(*iolat), gfp, node); | |
954 | if (!iolat) | |
955 | return NULL; | |
1fa2840e JB |
956 | iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat), |
957 | __alignof__(struct latency_stat), gfp); | |
d7067512 JB |
958 | if (!iolat->stats) { |
959 | kfree(iolat); | |
960 | return NULL; | |
961 | } | |
962 | return &iolat->pd; | |
963 | } | |
964 | ||
965 | static void iolatency_pd_init(struct blkg_policy_data *pd) | |
966 | { | |
967 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
968 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
969 | struct rq_qos *rqos = blkcg_rq_qos(blkg->q); | |
970 | struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); | |
971 | u64 now = ktime_to_ns(ktime_get()); | |
972 | int cpu; | |
973 | ||
1fa2840e JB |
974 | if (blk_queue_nonrot(blkg->q)) |
975 | iolat->ssd = true; | |
976 | else | |
977 | iolat->ssd = false; | |
978 | ||
d7067512 | 979 | for_each_possible_cpu(cpu) { |
1fa2840e | 980 | struct latency_stat *stat; |
d7067512 | 981 | stat = per_cpu_ptr(iolat->stats, cpu); |
1fa2840e | 982 | latency_stat_init(iolat, stat); |
d7067512 JB |
983 | } |
984 | ||
451bb7c3 | 985 | latency_stat_init(iolat, &iolat->cur_stat); |
d7067512 JB |
986 | rq_wait_init(&iolat->rq_wait); |
987 | spin_lock_init(&iolat->child_lat.lock); | |
ff4cee08 | 988 | iolat->rq_depth.queue_depth = blkg->q->nr_requests; |
a284390b | 989 | iolat->rq_depth.max_depth = UINT_MAX; |
d7067512 JB |
990 | iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth; |
991 | iolat->blkiolat = blkiolat; | |
992 | iolat->cur_win_nsec = 100 * NSEC_PER_MSEC; | |
993 | atomic64_set(&iolat->window_start, now); | |
994 | ||
995 | /* | |
996 | * We init things in list order, so the pd for the parent may not be | |
997 | * init'ed yet for whatever reason. | |
998 | */ | |
999 | if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) { | |
1000 | struct iolatency_grp *parent = blkg_to_lat(blkg->parent); | |
1001 | atomic_set(&iolat->scale_cookie, | |
1002 | atomic_read(&parent->child_lat.scale_cookie)); | |
1003 | } else { | |
1004 | atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE); | |
1005 | } | |
1006 | ||
1007 | atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE); | |
1008 | } | |
1009 | ||
1010 | static void iolatency_pd_offline(struct blkg_policy_data *pd) | |
1011 | { | |
1012 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1013 | struct blkcg_gq *blkg = lat_to_blkg(iolat); | |
8c772a9b LB |
1014 | struct blk_iolatency *blkiolat = iolat->blkiolat; |
1015 | int ret; | |
d7067512 | 1016 | |
8c772a9b LB |
1017 | ret = iolatency_set_min_lat_nsec(blkg, 0); |
1018 | if (ret == 1) | |
1019 | atomic_inc(&blkiolat->enabled); | |
1020 | if (ret == -1) | |
1021 | atomic_dec(&blkiolat->enabled); | |
d7067512 JB |
1022 | iolatency_clear_scaling(blkg); |
1023 | } | |
1024 | ||
1025 | static void iolatency_pd_free(struct blkg_policy_data *pd) | |
1026 | { | |
1027 | struct iolatency_grp *iolat = pd_to_lat(pd); | |
1028 | free_percpu(iolat->stats); | |
1029 | kfree(iolat); | |
1030 | } | |
1031 | ||
1032 | static struct cftype iolatency_files[] = { | |
1033 | { | |
1034 | .name = "latency", | |
1035 | .flags = CFTYPE_NOT_ON_ROOT, | |
1036 | .seq_show = iolatency_print_limit, | |
1037 | .write = iolatency_set_limit, | |
1038 | }, | |
1039 | {} | |
1040 | }; | |
1041 | ||
1042 | static struct blkcg_policy blkcg_policy_iolatency = { | |
1043 | .dfl_cftypes = iolatency_files, | |
1044 | .pd_alloc_fn = iolatency_pd_alloc, | |
1045 | .pd_init_fn = iolatency_pd_init, | |
1046 | .pd_offline_fn = iolatency_pd_offline, | |
1047 | .pd_free_fn = iolatency_pd_free, | |
1048 | .pd_stat_fn = iolatency_pd_stat, | |
1049 | }; | |
1050 | ||
1051 | static int __init iolatency_init(void) | |
1052 | { | |
1053 | return blkcg_policy_register(&blkcg_policy_iolatency); | |
1054 | } | |
1055 | ||
1056 | static void __exit iolatency_exit(void) | |
1057 | { | |
1058 | return blkcg_policy_unregister(&blkcg_policy_iolatency); | |
1059 | } | |
1060 | ||
1061 | module_init(iolatency_init); | |
1062 | module_exit(iolatency_exit); |