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