1// SPDX-License-Identifier: GPL-2.0 2/* 3 * The Kyber I/O scheduler. Controls latency by throttling queue depths using 4 * scalable techniques. 5 * 6 * Copyright (C) 2017 Facebook 7 */ 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_POINTS 23#include <trace/events/kyber.h> 24 25/* 26 * Scheduling domains: the device is divided into multiple domains based on the 27 * 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 of 47 * asynchronous requests, we reserve 25% of requests for synchronous 48 * 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 the 57 * device with only a fraction of the maximum possible queue depth. So, we cap 58 * 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 scheduling 78 * 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 relative 89 * to the target latency: 90 * 91 * <= 1/4 * target latency 92 * <= 1/2 * target latency 93 * <= 3/4 * target latency 94 * <= target latency 95 * <= 1 1/4 * target latency 96 * <= 1 1/2 * target latency 97 * <= 1 3/4 * target latency 98 * > 1 3/4 * target latency 99 */ 100enum { 101 /* 102 * The width of the latency histogram buckets is 103 * 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 after 117 * 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 scheduling 131 * 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 requests 156 * 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 for 162 * 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 there 224 * 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 passes 241 * 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 indicate 299 * congestion in the device. Note that we use the p90; we don't want to 300 * 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 was 313 * 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 not 324 * necessarily have enough samples to calculate the latency 325 * percentiles during the same window, so we have to remember 326 * 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 we 328 * 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 the 345 * latency target. E.g., if the p99 is 3/4 of the target, then 346 * we throttle down to 3/4 of the current depth, and if the p99 347 * 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 else 607 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 is 720 * run when one becomes available. Note that this is serialized on 721 * 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 wait 731 * 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 ourselves 738 * from the wait queue to ensure that all wake ups make forward 739 * progress. It's possible that the waker already deleted the entry 740 * between the !list_empty_careful() check and us grabbing the lock, but 741 * 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 a 766 * 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 should 768 * leave the requests in the kcqs so that they can be merged. Note that 769 * khd->lock serializes the flushes, so if we observed any bit set in 770 * 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 request 814 * 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 original 829 * 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 else 836 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_STORE 890 891#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_NULL 896}; 897#undef KYBER_LAT_ATTR 898 899#ifdef CONFIG_BLK_DEBUG_FS 900#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_ATTRS 959 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_ATTRS 998 999#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_ATTRS 1012#endif 1013 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_FS 1032 .queue_debugfs_attrs = kyber_queue_debugfs_attrs, 1033 .hctx_debugfs_attrs = kyber_hctx_debugfs_attrs, 1034#endif 1035 .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