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1// SPDX-License-Identifier: GPL-2.02/*3 * The Kyber I/O scheduler. Controls latency by throttling queue depths using4 * scalable techniques.5 *6 * Copyright (C) 2017 Facebook7 */8 9#include <linux/kernel.h>10#include <linux/blkdev.h>11#include <linux/module.h>12#include <linux/sbitmap.h>13 14#include <trace/events/block.h>15 16#include "elevator.h"17#include "blk.h"18#include "blk-mq.h"19#include "blk-mq-debugfs.h"20#include "blk-mq-sched.h"21 22#define CREATE_TRACE_POINTS23#include <trace/events/kyber.h>24 25/*26 * Scheduling domains: the device is divided into multiple domains based on the27 * request type.28 */29enum {30 KYBER_READ,31 KYBER_WRITE,32 KYBER_DISCARD,33 KYBER_OTHER,34 KYBER_NUM_DOMAINS,35};36 37static const char *kyber_domain_names[] = {38 [KYBER_READ] = "READ",39 [KYBER_WRITE] = "WRITE",40 [KYBER_DISCARD] = "DISCARD",41 [KYBER_OTHER] = "OTHER",42};43 44enum {45 /*46 * In order to prevent starvation of synchronous requests by a flood of47 * asynchronous requests, we reserve 25% of requests for synchronous48 * operations.49 */50 KYBER_ASYNC_PERCENT = 75,51};52 53/*54 * Maximum device-wide depth for each scheduling domain.55 *56 * Even for fast devices with lots of tags like NVMe, you can saturate the57 * device with only a fraction of the maximum possible queue depth. So, we cap58 * these to a reasonable value.59 */60static const unsigned int kyber_depth[] = {61 [KYBER_READ] = 256,62 [KYBER_WRITE] = 128,63 [KYBER_DISCARD] = 64,64 [KYBER_OTHER] = 16,65};66 67/*68 * Default latency targets for each scheduling domain.69 */70static const u64 kyber_latency_targets[] = {71 [KYBER_READ] = 2ULL * NSEC_PER_MSEC,72 [KYBER_WRITE] = 10ULL * NSEC_PER_MSEC,73 [KYBER_DISCARD] = 5ULL * NSEC_PER_SEC,74};75 76/*77 * Batch size (number of requests we'll dispatch in a row) for each scheduling78 * domain.79 */80static const unsigned int kyber_batch_size[] = {81 [KYBER_READ] = 16,82 [KYBER_WRITE] = 8,83 [KYBER_DISCARD] = 1,84 [KYBER_OTHER] = 1,85};86 87/*88 * Requests latencies are recorded in a histogram with buckets defined relative89 * to the target latency:90 *91 * <= 1/4 * target latency92 * <= 1/2 * target latency93 * <= 3/4 * target latency94 * <= target latency95 * <= 1 1/4 * target latency96 * <= 1 1/2 * target latency97 * <= 1 3/4 * target latency98 * > 1 3/4 * target latency99 */100enum {101 /*102 * The width of the latency histogram buckets is103 * 1 / (1 << KYBER_LATENCY_SHIFT) * target latency.104 */105 KYBER_LATENCY_SHIFT = 2,106 /*107 * The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency,108 * thus, "good".109 */110 KYBER_GOOD_BUCKETS = 1 << KYBER_LATENCY_SHIFT,111 /* There are also (1 << KYBER_LATENCY_SHIFT) "bad" buckets. */112 KYBER_LATENCY_BUCKETS = 2 << KYBER_LATENCY_SHIFT,113};114 115/*116 * We measure both the total latency and the I/O latency (i.e., latency after117 * submitting to the device).118 */119enum {120 KYBER_TOTAL_LATENCY,121 KYBER_IO_LATENCY,122};123 124static const char *kyber_latency_type_names[] = {125 [KYBER_TOTAL_LATENCY] = "total",126 [KYBER_IO_LATENCY] = "I/O",127};128 129/*130 * Per-cpu latency histograms: total latency and I/O latency for each scheduling131 * domain except for KYBER_OTHER.132 */133struct kyber_cpu_latency {134 atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];135};136 137/*138 * There is a same mapping between ctx & hctx and kcq & khd,139 * we use request->mq_ctx->index_hw to index the kcq in khd.140 */141struct kyber_ctx_queue {142 /*143 * Used to ensure operations on rq_list and kcq_map to be an atmoic one.144 * Also protect the rqs on rq_list when merge.145 */146 spinlock_t lock;147 struct list_head rq_list[KYBER_NUM_DOMAINS];148} ____cacheline_aligned_in_smp;149 150struct kyber_queue_data {151 struct request_queue *q;152 dev_t dev;153 154 /*155 * Each scheduling domain has a limited number of in-flight requests156 * device-wide, limited by these tokens.157 */158 struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS];159 160 /*161 * Async request percentage, converted to per-word depth for162 * sbitmap_get_shallow().163 */164 unsigned int async_depth;165 166 struct kyber_cpu_latency __percpu *cpu_latency;167 168 /* Timer for stats aggregation and adjusting domain tokens. */169 struct timer_list timer;170 171 unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];172 173 unsigned long latency_timeout[KYBER_OTHER];174 175 int domain_p99[KYBER_OTHER];176 177 /* Target latencies in nanoseconds. */178 u64 latency_targets[KYBER_OTHER];179};180 181struct kyber_hctx_data {182 spinlock_t lock;183 struct list_head rqs[KYBER_NUM_DOMAINS];184 unsigned int cur_domain;185 unsigned int batching;186 struct kyber_ctx_queue *kcqs;187 struct sbitmap kcq_map[KYBER_NUM_DOMAINS];188 struct sbq_wait domain_wait[KYBER_NUM_DOMAINS];189 struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS];190 atomic_t wait_index[KYBER_NUM_DOMAINS];191};192 193static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,194 void *key);195 196static unsigned int kyber_sched_domain(blk_opf_t opf)197{198 switch (opf & REQ_OP_MASK) {199 case REQ_OP_READ:200 return KYBER_READ;201 case REQ_OP_WRITE:202 return KYBER_WRITE;203 case REQ_OP_DISCARD:204 return KYBER_DISCARD;205 default:206 return KYBER_OTHER;207 }208}209 210static void flush_latency_buckets(struct kyber_queue_data *kqd,211 struct kyber_cpu_latency *cpu_latency,212 unsigned int sched_domain, unsigned int type)213{214 unsigned int *buckets = kqd->latency_buckets[sched_domain][type];215 atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];216 unsigned int bucket;217 218 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)219 buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);220}221 222/*223 * Calculate the histogram bucket with the given percentile rank, or -1 if there224 * aren't enough samples yet.225 */226static int calculate_percentile(struct kyber_queue_data *kqd,227 unsigned int sched_domain, unsigned int type,228 unsigned int percentile)229{230 unsigned int *buckets = kqd->latency_buckets[sched_domain][type];231 unsigned int bucket, samples = 0, percentile_samples;232 233 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)234 samples += buckets[bucket];235 236 if (!samples)237 return -1;238 239 /*240 * We do the calculation once we have 500 samples or one second passes241 * since the first sample was recorded, whichever comes first.242 */243 if (!kqd->latency_timeout[sched_domain])244 kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL);245 if (samples < 500 &&246 time_is_after_jiffies(kqd->latency_timeout[sched_domain])) {247 return -1;248 }249 kqd->latency_timeout[sched_domain] = 0;250 251 percentile_samples = DIV_ROUND_UP(samples * percentile, 100);252 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) {253 if (buckets[bucket] >= percentile_samples)254 break;255 percentile_samples -= buckets[bucket];256 }257 memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));258 259 trace_kyber_latency(kqd->dev, kyber_domain_names[sched_domain],260 kyber_latency_type_names[type], percentile,261 bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);262 263 return bucket;264}265 266static void kyber_resize_domain(struct kyber_queue_data *kqd,267 unsigned int sched_domain, unsigned int depth)268{269 depth = clamp(depth, 1U, kyber_depth[sched_domain]);270 if (depth != kqd->domain_tokens[sched_domain].sb.depth) {271 sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);272 trace_kyber_adjust(kqd->dev, kyber_domain_names[sched_domain],273 depth);274 }275}276 277static void kyber_timer_fn(struct timer_list *t)278{279 struct kyber_queue_data *kqd = from_timer(kqd, t, timer);280 unsigned int sched_domain;281 int cpu;282 bool bad = false;283 284 /* Sum all of the per-cpu latency histograms. */285 for_each_online_cpu(cpu) {286 struct kyber_cpu_latency *cpu_latency;287 288 cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu);289 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {290 flush_latency_buckets(kqd, cpu_latency, sched_domain,291 KYBER_TOTAL_LATENCY);292 flush_latency_buckets(kqd, cpu_latency, sched_domain,293 KYBER_IO_LATENCY);294 }295 }296 297 /*298 * Check if any domains have a high I/O latency, which might indicate299 * congestion in the device. Note that we use the p90; we don't want to300 * be too sensitive to outliers here.301 */302 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {303 int p90;304 305 p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,306 90);307 if (p90 >= KYBER_GOOD_BUCKETS)308 bad = true;309 }310 311 /*312 * Adjust the scheduling domain depths. If we determined that there was313 * congestion, we throttle all domains with good latencies. Either way,314 * we ease up on throttling domains with bad latencies.315 */316 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {317 unsigned int orig_depth, depth;318 int p99;319 320 p99 = calculate_percentile(kqd, sched_domain,321 KYBER_TOTAL_LATENCY, 99);322 /*323 * This is kind of subtle: different domains will not324 * necessarily have enough samples to calculate the latency325 * percentiles during the same window, so we have to remember326 * the p99 for the next time we observe congestion; once we do,327 * we don't want to throttle again until we get more data, so we328 * reset it to -1.329 */330 if (bad) {331 if (p99 < 0)332 p99 = kqd->domain_p99[sched_domain];333 kqd->domain_p99[sched_domain] = -1;334 } else if (p99 >= 0) {335 kqd->domain_p99[sched_domain] = p99;336 }337 if (p99 < 0)338 continue;339 340 /*341 * If this domain has bad latency, throttle less. Otherwise,342 * throttle more iff we determined that there is congestion.343 *344 * The new depth is scaled linearly with the p99 latency vs the345 * latency target. E.g., if the p99 is 3/4 of the target, then346 * we throttle down to 3/4 of the current depth, and if the p99347 * is 2x the target, then we double the depth.348 */349 if (bad || p99 >= KYBER_GOOD_BUCKETS) {350 orig_depth = kqd->domain_tokens[sched_domain].sb.depth;351 depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT;352 kyber_resize_domain(kqd, sched_domain, depth);353 }354 }355}356 357static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)358{359 struct kyber_queue_data *kqd;360 int ret = -ENOMEM;361 int i;362 363 kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);364 if (!kqd)365 goto err;366 367 kqd->q = q;368 kqd->dev = disk_devt(q->disk);369 370 kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,371 GFP_KERNEL | __GFP_ZERO);372 if (!kqd->cpu_latency)373 goto err_kqd;374 375 timer_setup(&kqd->timer, kyber_timer_fn, 0);376 377 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {378 WARN_ON(!kyber_depth[i]);379 WARN_ON(!kyber_batch_size[i]);380 ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],381 kyber_depth[i], -1, false,382 GFP_KERNEL, q->node);383 if (ret) {384 while (--i >= 0)385 sbitmap_queue_free(&kqd->domain_tokens[i]);386 goto err_buckets;387 }388 }389 390 for (i = 0; i < KYBER_OTHER; i++) {391 kqd->domain_p99[i] = -1;392 kqd->latency_targets[i] = kyber_latency_targets[i];393 }394 395 return kqd;396 397err_buckets:398 free_percpu(kqd->cpu_latency);399err_kqd:400 kfree(kqd);401err:402 return ERR_PTR(ret);403}404 405static int kyber_init_sched(struct request_queue *q, struct elevator_type *e)406{407 struct kyber_queue_data *kqd;408 struct elevator_queue *eq;409 410 eq = elevator_alloc(q, e);411 if (!eq)412 return -ENOMEM;413 414 kqd = kyber_queue_data_alloc(q);415 if (IS_ERR(kqd)) {416 kobject_put(&eq->kobj);417 return PTR_ERR(kqd);418 }419 420 blk_stat_enable_accounting(q);421 422 blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);423 424 eq->elevator_data = kqd;425 q->elevator = eq;426 427 return 0;428}429 430static void kyber_exit_sched(struct elevator_queue *e)431{432 struct kyber_queue_data *kqd = e->elevator_data;433 int i;434 435 timer_shutdown_sync(&kqd->timer);436 blk_stat_disable_accounting(kqd->q);437 438 for (i = 0; i < KYBER_NUM_DOMAINS; i++)439 sbitmap_queue_free(&kqd->domain_tokens[i]);440 free_percpu(kqd->cpu_latency);441 kfree(kqd);442}443 444static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)445{446 unsigned int i;447 448 spin_lock_init(&kcq->lock);449 for (i = 0; i < KYBER_NUM_DOMAINS; i++)450 INIT_LIST_HEAD(&kcq->rq_list[i]);451}452 453static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)454{455 struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;456 struct blk_mq_tags *tags = hctx->sched_tags;457 unsigned int shift = tags->bitmap_tags.sb.shift;458 459 kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;460 461 sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth);462}463 464static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)465{466 struct kyber_hctx_data *khd;467 int i;468 469 khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);470 if (!khd)471 return -ENOMEM;472 473 khd->kcqs = kmalloc_array_node(hctx->nr_ctx,474 sizeof(struct kyber_ctx_queue),475 GFP_KERNEL, hctx->numa_node);476 if (!khd->kcqs)477 goto err_khd;478 479 for (i = 0; i < hctx->nr_ctx; i++)480 kyber_ctx_queue_init(&khd->kcqs[i]);481 482 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {483 if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,484 ilog2(8), GFP_KERNEL, hctx->numa_node,485 false, false)) {486 while (--i >= 0)487 sbitmap_free(&khd->kcq_map[i]);488 goto err_kcqs;489 }490 }491 492 spin_lock_init(&khd->lock);493 494 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {495 INIT_LIST_HEAD(&khd->rqs[i]);496 khd->domain_wait[i].sbq = NULL;497 init_waitqueue_func_entry(&khd->domain_wait[i].wait,498 kyber_domain_wake);499 khd->domain_wait[i].wait.private = hctx;500 INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry);501 atomic_set(&khd->wait_index[i], 0);502 }503 504 khd->cur_domain = 0;505 khd->batching = 0;506 507 hctx->sched_data = khd;508 kyber_depth_updated(hctx);509 510 return 0;511 512err_kcqs:513 kfree(khd->kcqs);514err_khd:515 kfree(khd);516 return -ENOMEM;517}518 519static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)520{521 struct kyber_hctx_data *khd = hctx->sched_data;522 int i;523 524 for (i = 0; i < KYBER_NUM_DOMAINS; i++)525 sbitmap_free(&khd->kcq_map[i]);526 kfree(khd->kcqs);527 kfree(hctx->sched_data);528}529 530static int rq_get_domain_token(struct request *rq)531{532 return (long)rq->elv.priv[0];533}534 535static void rq_set_domain_token(struct request *rq, int token)536{537 rq->elv.priv[0] = (void *)(long)token;538}539 540static void rq_clear_domain_token(struct kyber_queue_data *kqd,541 struct request *rq)542{543 unsigned int sched_domain;544 int nr;545 546 nr = rq_get_domain_token(rq);547 if (nr != -1) {548 sched_domain = kyber_sched_domain(rq->cmd_flags);549 sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,550 rq->mq_ctx->cpu);551 }552}553 554static void kyber_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data)555{556 /*557 * We use the scheduler tags as per-hardware queue queueing tokens.558 * Async requests can be limited at this stage.559 */560 if (!op_is_sync(opf)) {561 struct kyber_queue_data *kqd = data->q->elevator->elevator_data;562 563 data->shallow_depth = kqd->async_depth;564 }565}566 567static bool kyber_bio_merge(struct request_queue *q, struct bio *bio,568 unsigned int nr_segs)569{570 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);571 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);572 struct kyber_hctx_data *khd = hctx->sched_data;573 struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw[hctx->type]];574 unsigned int sched_domain = kyber_sched_domain(bio->bi_opf);575 struct list_head *rq_list = &kcq->rq_list[sched_domain];576 bool merged;577 578 spin_lock(&kcq->lock);579 merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);580 spin_unlock(&kcq->lock);581 582 return merged;583}584 585static void kyber_prepare_request(struct request *rq)586{587 rq_set_domain_token(rq, -1);588}589 590static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx,591 struct list_head *rq_list,592 blk_insert_t flags)593{594 struct kyber_hctx_data *khd = hctx->sched_data;595 struct request *rq, *next;596 597 list_for_each_entry_safe(rq, next, rq_list, queuelist) {598 unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags);599 struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw[hctx->type]];600 struct list_head *head = &kcq->rq_list[sched_domain];601 602 spin_lock(&kcq->lock);603 trace_block_rq_insert(rq);604 if (flags & BLK_MQ_INSERT_AT_HEAD)605 list_move(&rq->queuelist, head);606 else607 list_move_tail(&rq->queuelist, head);608 sbitmap_set_bit(&khd->kcq_map[sched_domain],609 rq->mq_ctx->index_hw[hctx->type]);610 spin_unlock(&kcq->lock);611 }612}613 614static void kyber_finish_request(struct request *rq)615{616 struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;617 618 rq_clear_domain_token(kqd, rq);619}620 621static void add_latency_sample(struct kyber_cpu_latency *cpu_latency,622 unsigned int sched_domain, unsigned int type,623 u64 target, u64 latency)624{625 unsigned int bucket;626 u64 divisor;627 628 if (latency > 0) {629 divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1);630 bucket = min_t(unsigned int, div64_u64(latency - 1, divisor),631 KYBER_LATENCY_BUCKETS - 1);632 } else {633 bucket = 0;634 }635 636 atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]);637}638 639static void kyber_completed_request(struct request *rq, u64 now)640{641 struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;642 struct kyber_cpu_latency *cpu_latency;643 unsigned int sched_domain;644 u64 target;645 646 sched_domain = kyber_sched_domain(rq->cmd_flags);647 if (sched_domain == KYBER_OTHER)648 return;649 650 cpu_latency = get_cpu_ptr(kqd->cpu_latency);651 target = kqd->latency_targets[sched_domain];652 add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY,653 target, now - rq->start_time_ns);654 add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target,655 now - rq->io_start_time_ns);656 put_cpu_ptr(kqd->cpu_latency);657 658 timer_reduce(&kqd->timer, jiffies + HZ / 10);659}660 661struct flush_kcq_data {662 struct kyber_hctx_data *khd;663 unsigned int sched_domain;664 struct list_head *list;665};666 667static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data)668{669 struct flush_kcq_data *flush_data = data;670 struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr];671 672 spin_lock(&kcq->lock);673 list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain],674 flush_data->list);675 sbitmap_clear_bit(sb, bitnr);676 spin_unlock(&kcq->lock);677 678 return true;679}680 681static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd,682 unsigned int sched_domain,683 struct list_head *list)684{685 struct flush_kcq_data data = {686 .khd = khd,687 .sched_domain = sched_domain,688 .list = list,689 };690 691 sbitmap_for_each_set(&khd->kcq_map[sched_domain],692 flush_busy_kcq, &data);693}694 695static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags,696 void *key)697{698 struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private);699 struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait);700 701 sbitmap_del_wait_queue(wait);702 blk_mq_run_hw_queue(hctx, true);703 return 1;704}705 706static int kyber_get_domain_token(struct kyber_queue_data *kqd,707 struct kyber_hctx_data *khd,708 struct blk_mq_hw_ctx *hctx)709{710 unsigned int sched_domain = khd->cur_domain;711 struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain];712 struct sbq_wait *wait = &khd->domain_wait[sched_domain];713 struct sbq_wait_state *ws;714 int nr;715 716 nr = __sbitmap_queue_get(domain_tokens);717 718 /*719 * If we failed to get a domain token, make sure the hardware queue is720 * run when one becomes available. Note that this is serialized on721 * khd->lock, but we still need to be careful about the waker.722 */723 if (nr < 0 && list_empty_careful(&wait->wait.entry)) {724 ws = sbq_wait_ptr(domain_tokens,725 &khd->wait_index[sched_domain]);726 khd->domain_ws[sched_domain] = ws;727 sbitmap_add_wait_queue(domain_tokens, ws, wait);728 729 /*730 * Try again in case a token was freed before we got on the wait731 * queue.732 */733 nr = __sbitmap_queue_get(domain_tokens);734 }735 736 /*737 * If we got a token while we were on the wait queue, remove ourselves738 * from the wait queue to ensure that all wake ups make forward739 * progress. It's possible that the waker already deleted the entry740 * between the !list_empty_careful() check and us grabbing the lock, but741 * list_del_init() is okay with that.742 */743 if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) {744 ws = khd->domain_ws[sched_domain];745 spin_lock_irq(&ws->wait.lock);746 sbitmap_del_wait_queue(wait);747 spin_unlock_irq(&ws->wait.lock);748 }749 750 return nr;751}752 753static struct request *754kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,755 struct kyber_hctx_data *khd,756 struct blk_mq_hw_ctx *hctx)757{758 struct list_head *rqs;759 struct request *rq;760 int nr;761 762 rqs = &khd->rqs[khd->cur_domain];763 764 /*765 * If we already have a flushed request, then we just need to get a766 * token for it. Otherwise, if there are pending requests in the kcqs,767 * flush the kcqs, but only if we can get a token. If not, we should768 * leave the requests in the kcqs so that they can be merged. Note that769 * khd->lock serializes the flushes, so if we observed any bit set in770 * the kcq_map, we will always get a request.771 */772 rq = list_first_entry_or_null(rqs, struct request, queuelist);773 if (rq) {774 nr = kyber_get_domain_token(kqd, khd, hctx);775 if (nr >= 0) {776 khd->batching++;777 rq_set_domain_token(rq, nr);778 list_del_init(&rq->queuelist);779 return rq;780 } else {781 trace_kyber_throttled(kqd->dev,782 kyber_domain_names[khd->cur_domain]);783 }784 } else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) {785 nr = kyber_get_domain_token(kqd, khd, hctx);786 if (nr >= 0) {787 kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs);788 rq = list_first_entry(rqs, struct request, queuelist);789 khd->batching++;790 rq_set_domain_token(rq, nr);791 list_del_init(&rq->queuelist);792 return rq;793 } else {794 trace_kyber_throttled(kqd->dev,795 kyber_domain_names[khd->cur_domain]);796 }797 }798 799 /* There were either no pending requests or no tokens. */800 return NULL;801}802 803static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx)804{805 struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;806 struct kyber_hctx_data *khd = hctx->sched_data;807 struct request *rq;808 int i;809 810 spin_lock(&khd->lock);811 812 /*813 * First, if we are still entitled to batch, try to dispatch a request814 * from the batch.815 */816 if (khd->batching < kyber_batch_size[khd->cur_domain]) {817 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);818 if (rq)819 goto out;820 }821 822 /*823 * Either,824 * 1. We were no longer entitled to a batch.825 * 2. The domain we were batching didn't have any requests.826 * 3. The domain we were batching was out of tokens.827 *828 * Start another batch. Note that this wraps back around to the original829 * domain if no other domains have requests or tokens.830 */831 khd->batching = 0;832 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {833 if (khd->cur_domain == KYBER_NUM_DOMAINS - 1)834 khd->cur_domain = 0;835 else836 khd->cur_domain++;837 838 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);839 if (rq)840 goto out;841 }842 843 rq = NULL;844out:845 spin_unlock(&khd->lock);846 return rq;847}848 849static bool kyber_has_work(struct blk_mq_hw_ctx *hctx)850{851 struct kyber_hctx_data *khd = hctx->sched_data;852 int i;853 854 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {855 if (!list_empty_careful(&khd->rqs[i]) ||856 sbitmap_any_bit_set(&khd->kcq_map[i]))857 return true;858 }859 860 return false;861}862 863#define KYBER_LAT_SHOW_STORE(domain, name) \864static ssize_t kyber_##name##_lat_show(struct elevator_queue *e, \865 char *page) \866{ \867 struct kyber_queue_data *kqd = e->elevator_data; \868 \869 return sprintf(page, "%llu\n", kqd->latency_targets[domain]); \870} \871 \872static ssize_t kyber_##name##_lat_store(struct elevator_queue *e, \873 const char *page, size_t count) \874{ \875 struct kyber_queue_data *kqd = e->elevator_data; \876 unsigned long long nsec; \877 int ret; \878 \879 ret = kstrtoull(page, 10, &nsec); \880 if (ret) \881 return ret; \882 \883 kqd->latency_targets[domain] = nsec; \884 \885 return count; \886}887KYBER_LAT_SHOW_STORE(KYBER_READ, read);888KYBER_LAT_SHOW_STORE(KYBER_WRITE, write);889#undef KYBER_LAT_SHOW_STORE890 891#define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store)892static struct elv_fs_entry kyber_sched_attrs[] = {893 KYBER_LAT_ATTR(read),894 KYBER_LAT_ATTR(write),895 __ATTR_NULL896};897#undef KYBER_LAT_ATTR898 899#ifdef CONFIG_BLK_DEBUG_FS900#define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name) \901static int kyber_##name##_tokens_show(void *data, struct seq_file *m) \902{ \903 struct request_queue *q = data; \904 struct kyber_queue_data *kqd = q->elevator->elevator_data; \905 \906 sbitmap_queue_show(&kqd->domain_tokens[domain], m); \907 return 0; \908} \909 \910static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos) \911 __acquires(&khd->lock) \912{ \913 struct blk_mq_hw_ctx *hctx = m->private; \914 struct kyber_hctx_data *khd = hctx->sched_data; \915 \916 spin_lock(&khd->lock); \917 return seq_list_start(&khd->rqs[domain], *pos); \918} \919 \920static void *kyber_##name##_rqs_next(struct seq_file *m, void *v, \921 loff_t *pos) \922{ \923 struct blk_mq_hw_ctx *hctx = m->private; \924 struct kyber_hctx_data *khd = hctx->sched_data; \925 \926 return seq_list_next(v, &khd->rqs[domain], pos); \927} \928 \929static void kyber_##name##_rqs_stop(struct seq_file *m, void *v) \930 __releases(&khd->lock) \931{ \932 struct blk_mq_hw_ctx *hctx = m->private; \933 struct kyber_hctx_data *khd = hctx->sched_data; \934 \935 spin_unlock(&khd->lock); \936} \937 \938static const struct seq_operations kyber_##name##_rqs_seq_ops = { \939 .start = kyber_##name##_rqs_start, \940 .next = kyber_##name##_rqs_next, \941 .stop = kyber_##name##_rqs_stop, \942 .show = blk_mq_debugfs_rq_show, \943}; \944 \945static int kyber_##name##_waiting_show(void *data, struct seq_file *m) \946{ \947 struct blk_mq_hw_ctx *hctx = data; \948 struct kyber_hctx_data *khd = hctx->sched_data; \949 wait_queue_entry_t *wait = &khd->domain_wait[domain].wait; \950 \951 seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \952 return 0; \953}954KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)955KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write)956KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard)957KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other)958#undef KYBER_DEBUGFS_DOMAIN_ATTRS959 960static int kyber_async_depth_show(void *data, struct seq_file *m)961{962 struct request_queue *q = data;963 struct kyber_queue_data *kqd = q->elevator->elevator_data;964 965 seq_printf(m, "%u\n", kqd->async_depth);966 return 0;967}968 969static int kyber_cur_domain_show(void *data, struct seq_file *m)970{971 struct blk_mq_hw_ctx *hctx = data;972 struct kyber_hctx_data *khd = hctx->sched_data;973 974 seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);975 return 0;976}977 978static int kyber_batching_show(void *data, struct seq_file *m)979{980 struct blk_mq_hw_ctx *hctx = data;981 struct kyber_hctx_data *khd = hctx->sched_data;982 983 seq_printf(m, "%u\n", khd->batching);984 return 0;985}986 987#define KYBER_QUEUE_DOMAIN_ATTRS(name) \988 {#name "_tokens", 0400, kyber_##name##_tokens_show}989static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = {990 KYBER_QUEUE_DOMAIN_ATTRS(read),991 KYBER_QUEUE_DOMAIN_ATTRS(write),992 KYBER_QUEUE_DOMAIN_ATTRS(discard),993 KYBER_QUEUE_DOMAIN_ATTRS(other),994 {"async_depth", 0400, kyber_async_depth_show},995 {},996};997#undef KYBER_QUEUE_DOMAIN_ATTRS998 999#define KYBER_HCTX_DOMAIN_ATTRS(name) \1000 {#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops}, \1001 {#name "_waiting", 0400, kyber_##name##_waiting_show}1002static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = {1003 KYBER_HCTX_DOMAIN_ATTRS(read),1004 KYBER_HCTX_DOMAIN_ATTRS(write),1005 KYBER_HCTX_DOMAIN_ATTRS(discard),1006 KYBER_HCTX_DOMAIN_ATTRS(other),1007 {"cur_domain", 0400, kyber_cur_domain_show},1008 {"batching", 0400, kyber_batching_show},1009 {},1010};1011#undef KYBER_HCTX_DOMAIN_ATTRS1012#endif1013 1014static struct elevator_type kyber_sched = {1015 .ops = {1016 .init_sched = kyber_init_sched,1017 .exit_sched = kyber_exit_sched,1018 .init_hctx = kyber_init_hctx,1019 .exit_hctx = kyber_exit_hctx,1020 .limit_depth = kyber_limit_depth,1021 .bio_merge = kyber_bio_merge,1022 .prepare_request = kyber_prepare_request,1023 .insert_requests = kyber_insert_requests,1024 .finish_request = kyber_finish_request,1025 .requeue_request = kyber_finish_request,1026 .completed_request = kyber_completed_request,1027 .dispatch_request = kyber_dispatch_request,1028 .has_work = kyber_has_work,1029 .depth_updated = kyber_depth_updated,1030 },1031#ifdef CONFIG_BLK_DEBUG_FS1032 .queue_debugfs_attrs = kyber_queue_debugfs_attrs,1033 .hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,1034#endif1035 .elevator_attrs = kyber_sched_attrs,1036 .elevator_name = "kyber",1037 .elevator_owner = THIS_MODULE,1038};1039 1040static int __init kyber_init(void)1041{1042 return elv_register(&kyber_sched);1043}1044 1045static void __exit kyber_exit(void)1046{1047 elv_unregister(&kyber_sched);1048}1049 1050module_init(kyber_init);1051module_exit(kyber_exit);1052 1053MODULE_AUTHOR("Omar Sandoval");1054MODULE_LICENSE("GPL");1055MODULE_DESCRIPTION("Kyber I/O scheduler");1056