1 // SPDX-License-Identifier: GPL-2.0 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. 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 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> 73 #include <linux/sched/loadavg.h> 74 #include <linux/sched/signal.h> 75 #include <trace/events/block.h> 76 #include <linux/blk-mq.h> 77 #include <linux/blk-cgroup.h> 78 #include "blk-rq-qos.h" 79 #include "blk-stat.h" 80 #include "blk.h" 81 82 #define DEFAULT_SCALE_COOKIE 1000000U 83 84 static struct blkcg_policy blkcg_policy_iolatency; 85 struct iolatency_grp; 86 87 struct blk_iolatency { 88 struct rq_qos rqos; 89 struct timer_list timer; 90 atomic_t enabled; 91 }; 92 93 static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos) 94 { 95 return container_of(rqos, struct blk_iolatency, rqos); 96 } 97 98 static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat) 99 { 100 return atomic_read(&blkiolat->enabled) > 0; 101 } 102 103 struct child_latency_info { 104 spinlock_t lock; 105 106 /* Last time we adjusted the scale of everybody. */ 107 u64 last_scale_event; 108 109 /* The latency that we missed. */ 110 u64 scale_lat; 111 112 /* Total io's from all of our children for the last summation. */ 113 u64 nr_samples; 114 115 /* The guy who actually changed the latency numbers. */ 116 struct iolatency_grp *scale_grp; 117 118 /* Cookie to tell if we need to scale up or down. */ 119 atomic_t scale_cookie; 120 }; 121 122 struct percentile_stats { 123 u64 total; 124 u64 missed; 125 }; 126 127 struct latency_stat { 128 union { 129 struct percentile_stats ps; 130 struct blk_rq_stat rqs; 131 }; 132 }; 133 134 struct iolatency_grp { 135 struct blkg_policy_data pd; 136 struct latency_stat __percpu *stats; 137 struct latency_stat cur_stat; 138 struct blk_iolatency *blkiolat; 139 struct rq_depth rq_depth; 140 struct rq_wait rq_wait; 141 atomic64_t window_start; 142 atomic_t scale_cookie; 143 u64 min_lat_nsec; 144 u64 cur_win_nsec; 145 146 /* total running average of our io latency. */ 147 u64 lat_avg; 148 149 /* Our current number of IO's for the last summation. */ 150 u64 nr_samples; 151 152 bool ssd; 153 struct child_latency_info child_lat; 154 }; 155 156 #define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC) 157 #define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC 158 /* 159 * These are the constants used to fake the fixed-point moving average 160 * calculation just like load average. The call to calc_load() folds 161 * (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling 162 * window size is bucketed to try to approximately calculate average 163 * latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows 164 * elapse immediately. Note, windows only elapse with IO activity. Idle 165 * periods extend the most recent window. 166 */ 167 #define BLKIOLATENCY_NR_EXP_FACTORS 5 168 #define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \ 169 (BLKIOLATENCY_NR_EXP_FACTORS - 1)) 170 static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = { 171 2045, // exp(1/600) - 600 samples 172 2039, // exp(1/240) - 240 samples 173 2031, // exp(1/120) - 120 samples 174 2023, // exp(1/80) - 80 samples 175 2014, // exp(1/60) - 60 samples 176 }; 177 178 static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd) 179 { 180 return pd ? container_of(pd, struct iolatency_grp, pd) : NULL; 181 } 182 183 static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg) 184 { 185 return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency)); 186 } 187 188 static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat) 189 { 190 return pd_to_blkg(&iolat->pd); 191 } 192 193 static inline void latency_stat_init(struct iolatency_grp *iolat, 194 struct latency_stat *stat) 195 { 196 if (iolat->ssd) { 197 stat->ps.total = 0; 198 stat->ps.missed = 0; 199 } else 200 blk_rq_stat_init(&stat->rqs); 201 } 202 203 static inline void latency_stat_sum(struct iolatency_grp *iolat, 204 struct latency_stat *sum, 205 struct latency_stat *stat) 206 { 207 if (iolat->ssd) { 208 sum->ps.total += stat->ps.total; 209 sum->ps.missed += stat->ps.missed; 210 } else 211 blk_rq_stat_sum(&sum->rqs, &stat->rqs); 212 } 213 214 static inline void latency_stat_record_time(struct iolatency_grp *iolat, 215 u64 req_time) 216 { 217 struct latency_stat *stat = get_cpu_ptr(iolat->stats); 218 if (iolat->ssd) { 219 if (req_time >= iolat->min_lat_nsec) 220 stat->ps.missed++; 221 stat->ps.total++; 222 } else 223 blk_rq_stat_add(&stat->rqs, req_time); 224 put_cpu_ptr(stat); 225 } 226 227 static inline bool latency_sum_ok(struct iolatency_grp *iolat, 228 struct latency_stat *stat) 229 { 230 if (iolat->ssd) { 231 u64 thresh = div64_u64(stat->ps.total, 10); 232 thresh = max(thresh, 1ULL); 233 return stat->ps.missed < thresh; 234 } 235 return stat->rqs.mean <= iolat->min_lat_nsec; 236 } 237 238 static inline u64 latency_stat_samples(struct iolatency_grp *iolat, 239 struct latency_stat *stat) 240 { 241 if (iolat->ssd) 242 return stat->ps.total; 243 return stat->rqs.nr_samples; 244 } 245 246 static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat, 247 struct latency_stat *stat) 248 { 249 int exp_idx; 250 251 if (iolat->ssd) 252 return; 253 254 /* 255 * calc_load() takes in a number stored in fixed point representation. 256 * Because we are using this for IO time in ns, the values stored 257 * are significantly larger than the FIXED_1 denominator (2048). 258 * Therefore, rounding errors in the calculation are negligible and 259 * can be ignored. 260 */ 261 exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1, 262 div64_u64(iolat->cur_win_nsec, 263 BLKIOLATENCY_EXP_BUCKET_SIZE)); 264 iolat->lat_avg = calc_load(iolat->lat_avg, 265 iolatency_exp_factors[exp_idx], 266 stat->rqs.mean); 267 } 268 269 static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data) 270 { 271 atomic_dec(&rqw->inflight); 272 wake_up(&rqw->wait); 273 } 274 275 static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data) 276 { 277 struct iolatency_grp *iolat = private_data; 278 return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth); 279 } 280 281 static void __blkcg_iolatency_throttle(struct rq_qos *rqos, 282 struct iolatency_grp *iolat, 283 bool issue_as_root, 284 bool use_memdelay) 285 { 286 struct rq_wait *rqw = &iolat->rq_wait; 287 unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay); 288 289 if (use_delay) 290 blkcg_schedule_throttle(rqos->q, use_memdelay); 291 292 /* 293 * To avoid priority inversions we want to just take a slot if we are 294 * issuing as root. If we're being killed off there's no point in 295 * delaying things, we may have been killed by OOM so throttling may 296 * make recovery take even longer, so just let the IO's through so the 297 * task can go away. 298 */ 299 if (issue_as_root || fatal_signal_pending(current)) { 300 atomic_inc(&rqw->inflight); 301 return; 302 } 303 304 rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb); 305 } 306 307 #define SCALE_DOWN_FACTOR 2 308 #define SCALE_UP_FACTOR 4 309 310 static inline unsigned long scale_amount(unsigned long qd, bool up) 311 { 312 return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL); 313 } 314 315 /* 316 * We scale the qd down faster than we scale up, so we need to use this helper 317 * to adjust the scale_cookie accordingly so we don't prematurely get 318 * scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much. 319 * 320 * Each group has their own local copy of the last scale cookie they saw, so if 321 * the global scale cookie goes up or down they know which way they need to go 322 * based on their last knowledge of it. 323 */ 324 static void scale_cookie_change(struct blk_iolatency *blkiolat, 325 struct child_latency_info *lat_info, 326 bool up) 327 { 328 unsigned long qd = blkiolat->rqos.q->nr_requests; 329 unsigned long scale = scale_amount(qd, up); 330 unsigned long old = atomic_read(&lat_info->scale_cookie); 331 unsigned long max_scale = qd << 1; 332 unsigned long diff = 0; 333 334 if (old < DEFAULT_SCALE_COOKIE) 335 diff = DEFAULT_SCALE_COOKIE - old; 336 337 if (up) { 338 if (scale + old > DEFAULT_SCALE_COOKIE) 339 atomic_set(&lat_info->scale_cookie, 340 DEFAULT_SCALE_COOKIE); 341 else if (diff > qd) 342 atomic_inc(&lat_info->scale_cookie); 343 else 344 atomic_add(scale, &lat_info->scale_cookie); 345 } else { 346 /* 347 * We don't want to dig a hole so deep that it takes us hours to 348 * dig out of it. Just enough that we don't throttle/unthrottle 349 * with jagged workloads but can still unthrottle once pressure 350 * has sufficiently dissipated. 351 */ 352 if (diff > qd) { 353 if (diff < max_scale) 354 atomic_dec(&lat_info->scale_cookie); 355 } else { 356 atomic_sub(scale, &lat_info->scale_cookie); 357 } 358 } 359 } 360 361 /* 362 * Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the 363 * queue depth at a time so we don't get wild swings and hopefully dial in to 364 * fairer distribution of the overall queue depth. 365 */ 366 static void scale_change(struct iolatency_grp *iolat, bool up) 367 { 368 unsigned long qd = iolat->blkiolat->rqos.q->nr_requests; 369 unsigned long scale = scale_amount(qd, up); 370 unsigned long old = iolat->rq_depth.max_depth; 371 372 if (old > qd) 373 old = qd; 374 375 if (up) { 376 if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat))) 377 return; 378 379 if (old < qd) { 380 old += scale; 381 old = min(old, qd); 382 iolat->rq_depth.max_depth = old; 383 wake_up_all(&iolat->rq_wait.wait); 384 } 385 } else { 386 old >>= 1; 387 iolat->rq_depth.max_depth = max(old, 1UL); 388 } 389 } 390 391 /* Check our parent and see if the scale cookie has changed. */ 392 static void check_scale_change(struct iolatency_grp *iolat) 393 { 394 struct iolatency_grp *parent; 395 struct child_latency_info *lat_info; 396 unsigned int cur_cookie; 397 unsigned int our_cookie = atomic_read(&iolat->scale_cookie); 398 u64 scale_lat; 399 unsigned int old; 400 int direction = 0; 401 402 if (lat_to_blkg(iolat)->parent == NULL) 403 return; 404 405 parent = blkg_to_lat(lat_to_blkg(iolat)->parent); 406 if (!parent) 407 return; 408 409 lat_info = &parent->child_lat; 410 cur_cookie = atomic_read(&lat_info->scale_cookie); 411 scale_lat = READ_ONCE(lat_info->scale_lat); 412 413 if (cur_cookie < our_cookie) 414 direction = -1; 415 else if (cur_cookie > our_cookie) 416 direction = 1; 417 else 418 return; 419 420 old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie); 421 422 /* Somebody beat us to the punch, just bail. */ 423 if (old != our_cookie) 424 return; 425 426 if (direction < 0 && iolat->min_lat_nsec) { 427 u64 samples_thresh; 428 429 if (!scale_lat || iolat->min_lat_nsec <= scale_lat) 430 return; 431 432 /* 433 * Sometimes high priority groups are their own worst enemy, so 434 * instead of taking it out on some poor other group that did 5% 435 * or less of the IO's for the last summation just skip this 436 * scale down event. 437 */ 438 samples_thresh = lat_info->nr_samples * 5; 439 samples_thresh = max(1ULL, div64_u64(samples_thresh, 100)); 440 if (iolat->nr_samples <= samples_thresh) 441 return; 442 } 443 444 /* We're as low as we can go. */ 445 if (iolat->rq_depth.max_depth == 1 && direction < 0) { 446 blkcg_use_delay(lat_to_blkg(iolat)); 447 return; 448 } 449 450 /* We're back to the default cookie, unthrottle all the things. */ 451 if (cur_cookie == DEFAULT_SCALE_COOKIE) { 452 blkcg_clear_delay(lat_to_blkg(iolat)); 453 iolat->rq_depth.max_depth = UINT_MAX; 454 wake_up_all(&iolat->rq_wait.wait); 455 return; 456 } 457 458 scale_change(iolat, direction > 0); 459 } 460 461 static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio) 462 { 463 struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); 464 struct blkcg_gq *blkg = bio->bi_blkg; 465 bool issue_as_root = bio_issue_as_root_blkg(bio); 466 467 if (!blk_iolatency_enabled(blkiolat)) 468 return; 469 470 while (blkg && blkg->parent) { 471 struct iolatency_grp *iolat = blkg_to_lat(blkg); 472 if (!iolat) { 473 blkg = blkg->parent; 474 continue; 475 } 476 477 check_scale_change(iolat); 478 __blkcg_iolatency_throttle(rqos, iolat, issue_as_root, 479 (bio->bi_opf & REQ_SWAP) == REQ_SWAP); 480 blkg = blkg->parent; 481 } 482 if (!timer_pending(&blkiolat->timer)) 483 mod_timer(&blkiolat->timer, jiffies + HZ); 484 } 485 486 static void iolatency_record_time(struct iolatency_grp *iolat, 487 struct bio_issue *issue, u64 now, 488 bool issue_as_root) 489 { 490 u64 start = bio_issue_time(issue); 491 u64 req_time; 492 493 /* 494 * Have to do this so we are truncated to the correct time that our 495 * issue is truncated to. 496 */ 497 now = __bio_issue_time(now); 498 499 if (now <= start) 500 return; 501 502 req_time = now - start; 503 504 /* 505 * We don't want to count issue_as_root bio's in the cgroups latency 506 * statistics as it could skew the numbers downwards. 507 */ 508 if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) { 509 u64 sub = iolat->min_lat_nsec; 510 if (req_time < sub) 511 blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time); 512 return; 513 } 514 515 latency_stat_record_time(iolat, req_time); 516 } 517 518 #define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC) 519 #define BLKIOLATENCY_MIN_GOOD_SAMPLES 5 520 521 static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) 522 { 523 struct blkcg_gq *blkg = lat_to_blkg(iolat); 524 struct iolatency_grp *parent; 525 struct child_latency_info *lat_info; 526 struct latency_stat stat; 527 unsigned long flags; 528 int cpu; 529 530 latency_stat_init(iolat, &stat); 531 preempt_disable(); 532 for_each_online_cpu(cpu) { 533 struct latency_stat *s; 534 s = per_cpu_ptr(iolat->stats, cpu); 535 latency_stat_sum(iolat, &stat, s); 536 latency_stat_init(iolat, s); 537 } 538 preempt_enable(); 539 540 parent = blkg_to_lat(blkg->parent); 541 if (!parent) 542 return; 543 544 lat_info = &parent->child_lat; 545 546 iolat_update_total_lat_avg(iolat, &stat); 547 548 /* Everything is ok and we don't need to adjust the scale. */ 549 if (latency_sum_ok(iolat, &stat) && 550 atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE) 551 return; 552 553 /* Somebody beat us to the punch, just bail. */ 554 spin_lock_irqsave(&lat_info->lock, flags); 555 556 latency_stat_sum(iolat, &iolat->cur_stat, &stat); 557 lat_info->nr_samples -= iolat->nr_samples; 558 lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat); 559 iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat); 560 561 if ((lat_info->last_scale_event >= now || 562 now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME)) 563 goto out; 564 565 if (latency_sum_ok(iolat, &iolat->cur_stat) && 566 latency_sum_ok(iolat, &stat)) { 567 if (latency_stat_samples(iolat, &iolat->cur_stat) < 568 BLKIOLATENCY_MIN_GOOD_SAMPLES) 569 goto out; 570 if (lat_info->scale_grp == iolat) { 571 lat_info->last_scale_event = now; 572 scale_cookie_change(iolat->blkiolat, lat_info, true); 573 } 574 } else if (lat_info->scale_lat == 0 || 575 lat_info->scale_lat >= iolat->min_lat_nsec) { 576 lat_info->last_scale_event = now; 577 if (!lat_info->scale_grp || 578 lat_info->scale_lat > iolat->min_lat_nsec) { 579 WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec); 580 lat_info->scale_grp = iolat; 581 } 582 scale_cookie_change(iolat->blkiolat, lat_info, false); 583 } 584 latency_stat_init(iolat, &iolat->cur_stat); 585 out: 586 spin_unlock_irqrestore(&lat_info->lock, flags); 587 } 588 589 static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio) 590 { 591 struct blkcg_gq *blkg; 592 struct rq_wait *rqw; 593 struct iolatency_grp *iolat; 594 u64 window_start; 595 u64 now; 596 bool issue_as_root = bio_issue_as_root_blkg(bio); 597 bool enabled = false; 598 int inflight = 0; 599 600 blkg = bio->bi_blkg; 601 if (!blkg || !bio_flagged(bio, BIO_TRACKED)) 602 return; 603 604 iolat = blkg_to_lat(bio->bi_blkg); 605 if (!iolat) 606 return; 607 608 enabled = blk_iolatency_enabled(iolat->blkiolat); 609 if (!enabled) 610 return; 611 612 now = ktime_to_ns(ktime_get()); 613 while (blkg && blkg->parent) { 614 iolat = blkg_to_lat(blkg); 615 if (!iolat) { 616 blkg = blkg->parent; 617 continue; 618 } 619 rqw = &iolat->rq_wait; 620 621 inflight = atomic_dec_return(&rqw->inflight); 622 WARN_ON_ONCE(inflight < 0); 623 /* 624 * If bi_status is BLK_STS_AGAIN, the bio wasn't actually 625 * submitted, so do not account for it. 626 */ 627 if (iolat->min_lat_nsec && bio->bi_status != BLK_STS_AGAIN) { 628 iolatency_record_time(iolat, &bio->bi_issue, now, 629 issue_as_root); 630 window_start = atomic64_read(&iolat->window_start); 631 if (now > window_start && 632 (now - window_start) >= iolat->cur_win_nsec) { 633 if (atomic64_cmpxchg(&iolat->window_start, 634 window_start, now) == window_start) 635 iolatency_check_latencies(iolat, now); 636 } 637 } 638 wake_up(&rqw->wait); 639 blkg = blkg->parent; 640 } 641 } 642 643 static void blkcg_iolatency_exit(struct rq_qos *rqos) 644 { 645 struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); 646 647 del_timer_sync(&blkiolat->timer); 648 blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency); 649 kfree(blkiolat); 650 } 651 652 static struct rq_qos_ops blkcg_iolatency_ops = { 653 .throttle = blkcg_iolatency_throttle, 654 .done_bio = blkcg_iolatency_done_bio, 655 .exit = blkcg_iolatency_exit, 656 }; 657 658 static void blkiolatency_timer_fn(struct timer_list *t) 659 { 660 struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer); 661 struct blkcg_gq *blkg; 662 struct cgroup_subsys_state *pos_css; 663 u64 now = ktime_to_ns(ktime_get()); 664 665 rcu_read_lock(); 666 blkg_for_each_descendant_pre(blkg, pos_css, 667 blkiolat->rqos.q->root_blkg) { 668 struct iolatency_grp *iolat; 669 struct child_latency_info *lat_info; 670 unsigned long flags; 671 u64 cookie; 672 673 /* 674 * We could be exiting, don't access the pd unless we have a 675 * ref on the blkg. 676 */ 677 if (!blkg_tryget(blkg)) 678 continue; 679 680 iolat = blkg_to_lat(blkg); 681 if (!iolat) 682 goto next; 683 684 lat_info = &iolat->child_lat; 685 cookie = atomic_read(&lat_info->scale_cookie); 686 687 if (cookie >= DEFAULT_SCALE_COOKIE) 688 goto next; 689 690 spin_lock_irqsave(&lat_info->lock, flags); 691 if (lat_info->last_scale_event >= now) 692 goto next_lock; 693 694 /* 695 * We scaled down but don't have a scale_grp, scale up and carry 696 * on. 697 */ 698 if (lat_info->scale_grp == NULL) { 699 scale_cookie_change(iolat->blkiolat, lat_info, true); 700 goto next_lock; 701 } 702 703 /* 704 * It's been 5 seconds since our last scale event, clear the 705 * scale grp in case the group that needed the scale down isn't 706 * doing any IO currently. 707 */ 708 if (now - lat_info->last_scale_event >= 709 ((u64)NSEC_PER_SEC * 5)) 710 lat_info->scale_grp = NULL; 711 next_lock: 712 spin_unlock_irqrestore(&lat_info->lock, flags); 713 next: 714 blkg_put(blkg); 715 } 716 rcu_read_unlock(); 717 } 718 719 int blk_iolatency_init(struct request_queue *q) 720 { 721 struct blk_iolatency *blkiolat; 722 struct rq_qos *rqos; 723 int ret; 724 725 blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL); 726 if (!blkiolat) 727 return -ENOMEM; 728 729 rqos = &blkiolat->rqos; 730 rqos->id = RQ_QOS_LATENCY; 731 rqos->ops = &blkcg_iolatency_ops; 732 rqos->q = q; 733 734 rq_qos_add(q, rqos); 735 736 ret = blkcg_activate_policy(q, &blkcg_policy_iolatency); 737 if (ret) { 738 rq_qos_del(q, rqos); 739 kfree(blkiolat); 740 return ret; 741 } 742 743 timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0); 744 745 return 0; 746 } 747 748 /* 749 * return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise 750 * return 0. 751 */ 752 static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val) 753 { 754 struct iolatency_grp *iolat = blkg_to_lat(blkg); 755 u64 oldval = iolat->min_lat_nsec; 756 757 iolat->min_lat_nsec = val; 758 iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE); 759 iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec, 760 BLKIOLATENCY_MAX_WIN_SIZE); 761 762 if (!oldval && val) 763 return 1; 764 if (oldval && !val) { 765 blkcg_clear_delay(blkg); 766 return -1; 767 } 768 return 0; 769 } 770 771 static void iolatency_clear_scaling(struct blkcg_gq *blkg) 772 { 773 if (blkg->parent) { 774 struct iolatency_grp *iolat = blkg_to_lat(blkg->parent); 775 struct child_latency_info *lat_info; 776 if (!iolat) 777 return; 778 779 lat_info = &iolat->child_lat; 780 spin_lock(&lat_info->lock); 781 atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE); 782 lat_info->last_scale_event = 0; 783 lat_info->scale_grp = NULL; 784 lat_info->scale_lat = 0; 785 spin_unlock(&lat_info->lock); 786 } 787 } 788 789 static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf, 790 size_t nbytes, loff_t off) 791 { 792 struct blkcg *blkcg = css_to_blkcg(of_css(of)); 793 struct blkcg_gq *blkg; 794 struct blkg_conf_ctx ctx; 795 struct iolatency_grp *iolat; 796 char *p, *tok; 797 u64 lat_val = 0; 798 u64 oldval; 799 int ret; 800 int enable = 0; 801 802 ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx); 803 if (ret) 804 return ret; 805 806 iolat = blkg_to_lat(ctx.blkg); 807 p = ctx.body; 808 809 ret = -EINVAL; 810 while ((tok = strsep(&p, " "))) { 811 char key[16]; 812 char val[21]; /* 18446744073709551616 */ 813 814 if (sscanf(tok, "%15[^=]=%20s", key, val) != 2) 815 goto out; 816 817 if (!strcmp(key, "target")) { 818 u64 v; 819 820 if (!strcmp(val, "max")) 821 lat_val = 0; 822 else if (sscanf(val, "%llu", &v) == 1) 823 lat_val = v * NSEC_PER_USEC; 824 else 825 goto out; 826 } else { 827 goto out; 828 } 829 } 830 831 /* Walk up the tree to see if our new val is lower than it should be. */ 832 blkg = ctx.blkg; 833 oldval = iolat->min_lat_nsec; 834 835 enable = iolatency_set_min_lat_nsec(blkg, lat_val); 836 if (enable) { 837 if (!blk_get_queue(blkg->q)) { 838 ret = -ENODEV; 839 goto out; 840 } 841 842 blkg_get(blkg); 843 } 844 845 if (oldval != iolat->min_lat_nsec) { 846 iolatency_clear_scaling(blkg); 847 } 848 849 ret = 0; 850 out: 851 blkg_conf_finish(&ctx); 852 if (ret == 0 && enable) { 853 struct iolatency_grp *tmp = blkg_to_lat(blkg); 854 struct blk_iolatency *blkiolat = tmp->blkiolat; 855 856 blk_mq_freeze_queue(blkg->q); 857 858 if (enable == 1) 859 atomic_inc(&blkiolat->enabled); 860 else if (enable == -1) 861 atomic_dec(&blkiolat->enabled); 862 else 863 WARN_ON_ONCE(1); 864 865 blk_mq_unfreeze_queue(blkg->q); 866 867 blkg_put(blkg); 868 blk_put_queue(blkg->q); 869 } 870 return ret ?: nbytes; 871 } 872 873 static u64 iolatency_prfill_limit(struct seq_file *sf, 874 struct blkg_policy_data *pd, int off) 875 { 876 struct iolatency_grp *iolat = pd_to_lat(pd); 877 const char *dname = blkg_dev_name(pd->blkg); 878 879 if (!dname || !iolat->min_lat_nsec) 880 return 0; 881 seq_printf(sf, "%s target=%llu\n", 882 dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC)); 883 return 0; 884 } 885 886 static int iolatency_print_limit(struct seq_file *sf, void *v) 887 { 888 blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), 889 iolatency_prfill_limit, 890 &blkcg_policy_iolatency, seq_cft(sf)->private, false); 891 return 0; 892 } 893 894 static bool iolatency_ssd_stat(struct iolatency_grp *iolat, struct seq_file *s) 895 { 896 struct latency_stat stat; 897 int cpu; 898 899 latency_stat_init(iolat, &stat); 900 preempt_disable(); 901 for_each_online_cpu(cpu) { 902 struct latency_stat *s; 903 s = per_cpu_ptr(iolat->stats, cpu); 904 latency_stat_sum(iolat, &stat, s); 905 } 906 preempt_enable(); 907 908 if (iolat->rq_depth.max_depth == UINT_MAX) 909 seq_printf(s, " missed=%llu total=%llu depth=max", 910 (unsigned long long)stat.ps.missed, 911 (unsigned long long)stat.ps.total); 912 else 913 seq_printf(s, " missed=%llu total=%llu depth=%u", 914 (unsigned long long)stat.ps.missed, 915 (unsigned long long)stat.ps.total, 916 iolat->rq_depth.max_depth); 917 return true; 918 } 919 920 static bool iolatency_pd_stat(struct blkg_policy_data *pd, struct seq_file *s) 921 { 922 struct iolatency_grp *iolat = pd_to_lat(pd); 923 unsigned long long avg_lat; 924 unsigned long long cur_win; 925 926 if (!blkcg_debug_stats) 927 return false; 928 929 if (iolat->ssd) 930 return iolatency_ssd_stat(iolat, s); 931 932 avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC); 933 cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC); 934 if (iolat->rq_depth.max_depth == UINT_MAX) 935 seq_printf(s, " depth=max avg_lat=%llu win=%llu", 936 avg_lat, cur_win); 937 else 938 seq_printf(s, " depth=%u avg_lat=%llu win=%llu", 939 iolat->rq_depth.max_depth, avg_lat, cur_win); 940 return true; 941 } 942 943 static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, 944 struct request_queue *q, 945 struct blkcg *blkcg) 946 { 947 struct iolatency_grp *iolat; 948 949 iolat = kzalloc_node(sizeof(*iolat), gfp, q->node); 950 if (!iolat) 951 return NULL; 952 iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat), 953 __alignof__(struct latency_stat), gfp); 954 if (!iolat->stats) { 955 kfree(iolat); 956 return NULL; 957 } 958 return &iolat->pd; 959 } 960 961 static void iolatency_pd_init(struct blkg_policy_data *pd) 962 { 963 struct iolatency_grp *iolat = pd_to_lat(pd); 964 struct blkcg_gq *blkg = lat_to_blkg(iolat); 965 struct rq_qos *rqos = blkcg_rq_qos(blkg->q); 966 struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos); 967 u64 now = ktime_to_ns(ktime_get()); 968 int cpu; 969 970 if (blk_queue_nonrot(blkg->q)) 971 iolat->ssd = true; 972 else 973 iolat->ssd = false; 974 975 for_each_possible_cpu(cpu) { 976 struct latency_stat *stat; 977 stat = per_cpu_ptr(iolat->stats, cpu); 978 latency_stat_init(iolat, stat); 979 } 980 981 latency_stat_init(iolat, &iolat->cur_stat); 982 rq_wait_init(&iolat->rq_wait); 983 spin_lock_init(&iolat->child_lat.lock); 984 iolat->rq_depth.queue_depth = blkg->q->nr_requests; 985 iolat->rq_depth.max_depth = UINT_MAX; 986 iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth; 987 iolat->blkiolat = blkiolat; 988 iolat->cur_win_nsec = 100 * NSEC_PER_MSEC; 989 atomic64_set(&iolat->window_start, now); 990 991 /* 992 * We init things in list order, so the pd for the parent may not be 993 * init'ed yet for whatever reason. 994 */ 995 if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) { 996 struct iolatency_grp *parent = blkg_to_lat(blkg->parent); 997 atomic_set(&iolat->scale_cookie, 998 atomic_read(&parent->child_lat.scale_cookie)); 999 } else { 1000 atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE); 1001 } 1002 1003 atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE); 1004 } 1005 1006 static void iolatency_pd_offline(struct blkg_policy_data *pd) 1007 { 1008 struct iolatency_grp *iolat = pd_to_lat(pd); 1009 struct blkcg_gq *blkg = lat_to_blkg(iolat); 1010 struct blk_iolatency *blkiolat = iolat->blkiolat; 1011 int ret; 1012 1013 ret = iolatency_set_min_lat_nsec(blkg, 0); 1014 if (ret == 1) 1015 atomic_inc(&blkiolat->enabled); 1016 if (ret == -1) 1017 atomic_dec(&blkiolat->enabled); 1018 iolatency_clear_scaling(blkg); 1019 } 1020 1021 static void iolatency_pd_free(struct blkg_policy_data *pd) 1022 { 1023 struct iolatency_grp *iolat = pd_to_lat(pd); 1024 free_percpu(iolat->stats); 1025 kfree(iolat); 1026 } 1027 1028 static struct cftype iolatency_files[] = { 1029 { 1030 .name = "latency", 1031 .flags = CFTYPE_NOT_ON_ROOT, 1032 .seq_show = iolatency_print_limit, 1033 .write = iolatency_set_limit, 1034 }, 1035 {} 1036 }; 1037 1038 static struct blkcg_policy blkcg_policy_iolatency = { 1039 .dfl_cftypes = iolatency_files, 1040 .pd_alloc_fn = iolatency_pd_alloc, 1041 .pd_init_fn = iolatency_pd_init, 1042 .pd_offline_fn = iolatency_pd_offline, 1043 .pd_free_fn = iolatency_pd_free, 1044 .pd_stat_fn = iolatency_pd_stat, 1045 }; 1046 1047 static int __init iolatency_init(void) 1048 { 1049 return blkcg_policy_register(&blkcg_policy_iolatency); 1050 } 1051 1052 static void __exit iolatency_exit(void) 1053 { 1054 blkcg_policy_unregister(&blkcg_policy_iolatency); 1055 } 1056 1057 module_init(iolatency_init); 1058 module_exit(iolatency_exit); 1059