block/kyber-iosched.c

   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/blk-mq.h>
  12 #include <linux/elevator.h>
  13 #include <linux/module.h>
  14 #include <linux/sbitmap.h>
  15
  16 #include <trace/events/block.h>
  17
  18 #include "blk.h"
  19 #include "blk-mq.h"
  20 #include "blk-mq-debugfs.h"
  21 #include "blk-mq-sched.h"
  22 #include "blk-mq-tag.h"
  23
  24 #define CREATE_TRACE_POINTS
  25 #include <trace/events/kyber.h>
  26
  27 /*
  28  * Scheduling domains: the device is divided into multiple domains based on the
  29  * request type.
  30  */
  31 enum {
  32         KYBER_READ,
  33         KYBER_WRITE,
  34         KYBER_DISCARD,
  35         KYBER_OTHER,
  36         KYBER_NUM_DOMAINS,
  37 };
  38
  39 static const char *kyber_domain_names[] = {
  40         [KYBER_READ] = "READ",
  41         [KYBER_WRITE] = "WRITE",
  42         [KYBER_DISCARD] = "DISCARD",
  43         [KYBER_OTHER] = "OTHER",
  44 };
  45
  46 enum {
  47         /*
  48          * In order to prevent starvation of synchronous requests by a flood of
  49          * asynchronous requests, we reserve 25% of requests for synchronous
  50          * operations.
  51          */
  52         KYBER_ASYNC_PERCENT = 75,
  53 };
  54
  55 /*
  56  * Maximum device-wide depth for each scheduling domain.
  57  *
  58  * Even for fast devices with lots of tags like NVMe, you can saturate the
  59  * device with only a fraction of the maximum possible queue depth. So, we cap
  60  * these to a reasonable value.
  61  */
  62 static const unsigned int kyber_depth[] = {
  63         [KYBER_READ] = 256,
  64         [KYBER_WRITE] = 128,
  65         [KYBER_DISCARD] = 64,
  66         [KYBER_OTHER] = 16,
  67 };
  68
  69 /*
  70  * Default latency targets for each scheduling domain.
  71  */
  72 static const u64 kyber_latency_targets[] = {
  73         [KYBER_READ] = 2ULL * NSEC_PER_MSEC,
  74         [KYBER_WRITE] = 10ULL * NSEC_PER_MSEC,
  75         [KYBER_DISCARD] = 5ULL * NSEC_PER_SEC,
  76 };
  77
  78 /*
  79  * Batch size (number of requests we'll dispatch in a row) for each scheduling
  80  * domain.
  81  */
  82 static const unsigned int kyber_batch_size[] = {
  83         [KYBER_READ] = 16,
  84         [KYBER_WRITE] = 8,
  85         [KYBER_DISCARD] = 1,
  86         [KYBER_OTHER] = 1,
  87 };
  88
  89 /*
  90  * Requests latencies are recorded in a histogram with buckets defined relative
  91  * to the target latency:
  92  *
  93  * <= 1/4 * target latency
  94  * <= 1/2 * target latency
  95  * <= 3/4 * target latency
  96  * <= target latency
  97  * <= 1 1/4 * target latency
  98  * <= 1 1/2 * target latency
  99  * <= 1 3/4 * target latency
 100  * > 1 3/4 * target latency
 101  */
 102 enum {
 103         /*
 104          * The width of the latency histogram buckets is
 105          * 1 / (1 << KYBER_LATENCY_SHIFT) * target latency.
 106          */
 107         KYBER_LATENCY_SHIFT = 2,
 108         /*
 109          * The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency,
 110          * thus, "good".
 111          */
 112         KYBER_GOOD_BUCKETS = 1 << KYBER_LATENCY_SHIFT,
 113         /* There are also (1 << KYBER_LATENCY_SHIFT) "bad" buckets. */
 114         KYBER_LATENCY_BUCKETS = 2 << KYBER_LATENCY_SHIFT,
 115 };
 116
 117 /*
 118  * We measure both the total latency and the I/O latency (i.e., latency after
 119  * submitting to the device).
 120  */
 121 enum {
 122         KYBER_TOTAL_LATENCY,
 123         KYBER_IO_LATENCY,
 124 };
 125
 126 static const char *kyber_latency_type_names[] = {
 127         [KYBER_TOTAL_LATENCY] = "total",
 128         [KYBER_IO_LATENCY] = "I/O",
 129 };
 130
 131 /*
 132  * Per-cpu latency histograms: total latency and I/O latency for each scheduling
 133  * domain except for KYBER_OTHER.
 134  */
 135 struct kyber_cpu_latency {
 136         atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
 137 };
 138
 139 /*
 140  * There is a same mapping between ctx & hctx and kcq & khd,
 141  * we use request->mq_ctx->index_hw to index the kcq in khd.
 142  */
 143 struct kyber_ctx_queue {
 144         /*
 145          * Used to ensure operations on rq_list and kcq_map to be an atmoic one.
 146          * Also protect the rqs on rq_list when merge.
 147          */
 148         spinlock_t lock;
 149         struct list_head rq_list[KYBER_NUM_DOMAINS];
 150 } ____cacheline_aligned_in_smp;
 151
 152 struct kyber_queue_data {
 153         struct request_queue *q;
 154
 155         /*
 156          * Each scheduling domain has a limited number of in-flight requests
 157          * device-wide, limited by these tokens.
 158          */
 159         struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS];
 160
 161         /*
 162          * Async request percentage, converted to per-word depth for
 163          * sbitmap_get_shallow().
 164          */
 165         unsigned int async_depth;
 166
 167         struct kyber_cpu_latency __percpu *cpu_latency;
 168
 169         /* Timer for stats aggregation and adjusting domain tokens. */
 170         struct timer_list timer;
 171
 172         unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
 173
 174         unsigned long latency_timeout[KYBER_OTHER];
 175
 176         int domain_p99[KYBER_OTHER];
 177
 178         /* Target latencies in nanoseconds. */
 179         u64 latency_targets[KYBER_OTHER];
 180 };
 181
 182 struct kyber_hctx_data {
 183         spinlock_t lock;
 184         struct list_head rqs[KYBER_NUM_DOMAINS];
 185         unsigned int cur_domain;
 186         unsigned int batching;
 187         struct kyber_ctx_queue *kcqs;
 188         struct sbitmap kcq_map[KYBER_NUM_DOMAINS];
 189         struct sbq_wait domain_wait[KYBER_NUM_DOMAINS];
 190         struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS];
 191         atomic_t wait_index[KYBER_NUM_DOMAINS];
 192 };
 193
 194 static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
 195                              void *key);
 196
 197 static unsigned int kyber_sched_domain(unsigned int op)
 198 {
 199         switch (op & REQ_OP_MASK) {
 200         case REQ_OP_READ:
 201                 return KYBER_READ;
 202         case REQ_OP_WRITE:
 203                 return KYBER_WRITE;
 204         case REQ_OP_DISCARD:
 205                 return KYBER_DISCARD;
 206         default:
 207                 return KYBER_OTHER;
 208         }
 209 }
 210
 211 static void flush_latency_buckets(struct kyber_queue_data *kqd,
 212                                   struct kyber_cpu_latency *cpu_latency,
 213                                   unsigned int sched_domain, unsigned int type)
 214 {
 215         unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
 216         atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];
 217         unsigned int bucket;
 218
 219         for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
 220                 buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);
 221 }
 222
 223 /*
 224  * Calculate the histogram bucket with the given percentile rank, or -1 if there
 225  * aren't enough samples yet.
 226  */
 227 static int calculate_percentile(struct kyber_queue_data *kqd,
 228                                 unsigned int sched_domain, unsigned int type,
 229                                 unsigned int percentile)
 230 {
 231         unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
 232         unsigned int bucket, samples = 0, percentile_samples;
 233
 234         for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
 235                 samples += buckets[bucket];
 236
 237         if (!samples)
 238                 return -1;
 239
 240         /*
 241          * We do the calculation once we have 500 samples or one second passes
 242          * since the first sample was recorded, whichever comes first.
 243          */
 244         if (!kqd->latency_timeout[sched_domain])
 245                 kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL);
 246         if (samples < 500 &&
 247             time_is_after_jiffies(kqd->latency_timeout[sched_domain])) {
 248                 return -1;
 249         }
 250         kqd->latency_timeout[sched_domain] = 0;
 251
 252         percentile_samples = DIV_ROUND_UP(samples * percentile, 100);
 253         for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) {
 254                 if (buckets[bucket] >= percentile_samples)
 255                         break;
 256                 percentile_samples -= buckets[bucket];
 257         }
 258         memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));
 259
 260         trace_kyber_latency(kqd->q, kyber_domain_names[sched_domain],
 261                             kyber_latency_type_names[type], percentile,
 262                             bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);
 263
 264         return bucket;
 265 }
 266
 267 static void kyber_resize_domain(struct kyber_queue_data *kqd,
 268                                 unsigned int sched_domain, unsigned int depth)
 269 {
 270         depth = clamp(depth, 1U, kyber_depth[sched_domain]);
 271         if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
 272                 sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
 273                 trace_kyber_adjust(kqd->q, kyber_domain_names[sched_domain],
 274                                    depth);
 275         }
 276 }
 277
 278 static void kyber_timer_fn(struct timer_list *t)
 279 {
 280         struct kyber_queue_data *kqd = from_timer(kqd, t, timer);
 281         unsigned int sched_domain;
 282         int cpu;
 283         bool bad = false;
 284
 285         /* Sum all of the per-cpu latency histograms. */
 286         for_each_online_cpu(cpu) {
 287                 struct kyber_cpu_latency *cpu_latency;
 288
 289                 cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu);
 290                 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
 291                         flush_latency_buckets(kqd, cpu_latency, sched_domain,
 292                                               KYBER_TOTAL_LATENCY);
 293                         flush_latency_buckets(kqd, cpu_latency, sched_domain,
 294                                               KYBER_IO_LATENCY);
 295                 }
 296         }
 297
 298         /*
 299          * Check if any domains have a high I/O latency, which might indicate
 300          * congestion in the device. Note that we use the p90; we don't want to
 301          * be too sensitive to outliers here.
 302          */
 303         for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
 304                 int p90;
 305
 306                 p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,
 307                                            90);
 308                 if (p90 >= KYBER_GOOD_BUCKETS)
 309                         bad = true;
 310         }
 311
 312         /*
 313          * Adjust the scheduling domain depths. If we determined that there was
 314          * congestion, we throttle all domains with good latencies. Either way,
 315          * we ease up on throttling domains with bad latencies.
 316          */
 317         for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
 318                 unsigned int orig_depth, depth;
 319                 int p99;
 320
 321                 p99 = calculate_percentile(kqd, sched_domain,
 322                                            KYBER_TOTAL_LATENCY, 99);
 323                 /*
 324                  * This is kind of subtle: different domains will not
 325                  * necessarily have enough samples to calculate the latency
 326                  * percentiles during the same window, so we have to remember
 327                  * the p99 for the next time we observe congestion; once we do,
 328                  * we don't want to throttle again until we get more data, so we
 329                  * reset it to -1.
 330                  */
 331                 if (bad) {
 332                         if (p99 < 0)
 333                                 p99 = kqd->domain_p99[sched_domain];
 334                         kqd->domain_p99[sched_domain] = -1;
 335                 } else if (p99 >= 0) {
 336                         kqd->domain_p99[sched_domain] = p99;
 337                 }
 338                 if (p99 < 0)
 339                         continue;
 340
 341                 /*
 342                  * If this domain has bad latency, throttle less. Otherwise,
 343                  * throttle more iff we determined that there is congestion.
 344                  *
 345                  * The new depth is scaled linearly with the p99 latency vs the
 346                  * latency target. E.g., if the p99 is 3/4 of the target, then
 347                  * we throttle down to 3/4 of the current depth, and if the p99
 348                  * is 2x the target, then we double the depth.
 349                  */
 350                 if (bad || p99 >= KYBER_GOOD_BUCKETS) {
 351                         orig_depth = kqd->domain_tokens[sched_domain].sb.depth;
 352                         depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT;
 353                         kyber_resize_domain(kqd, sched_domain, depth);
 354                 }
 355         }
 356 }
 357
 358 static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
 359 {
 360         struct kyber_queue_data *kqd;
 361         int ret = -ENOMEM;
 362         int i;
 363
 364         kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
 365         if (!kqd)
 366                 goto err;
 367
 368         kqd->q = q;
 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
 397 err_buckets:
 398         free_percpu(kqd->cpu_latency);
 399 err_kqd:
 400         kfree(kqd);
 401 err:
 402         return ERR_PTR(ret);
 403 }
 404
 405 static 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         eq->elevator_data = kqd;
 423         q->elevator = eq;
 424
 425         return 0;
 426 }
 427
 428 static void kyber_exit_sched(struct elevator_queue *e)
 429 {
 430         struct kyber_queue_data *kqd = e->elevator_data;
 431         int i;
 432
 433         del_timer_sync(&kqd->timer);
 434
 435         for (i = 0; i < KYBER_NUM_DOMAINS; i++)
 436                 sbitmap_queue_free(&kqd->domain_tokens[i]);
 437         free_percpu(kqd->cpu_latency);
 438         kfree(kqd);
 439 }
 440
 441 static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
 442 {
 443         unsigned int i;
 444
 445         spin_lock_init(&kcq->lock);
 446         for (i = 0; i < KYBER_NUM_DOMAINS; i++)
 447                 INIT_LIST_HEAD(&kcq->rq_list[i]);
 448 }
 449
 450 static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
 451 {
 452         struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
 453         struct blk_mq_tags *tags = hctx->sched_tags;
 454         unsigned int shift = tags->bitmap_tags->sb.shift;
 455
 456         kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
 457
 458         sbitmap_queue_min_shallow_depth(tags->bitmap_tags, kqd->async_depth);
 459 }
 460
 461 static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 462 {
 463         struct kyber_hctx_data *khd;
 464         int i;
 465
 466         khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
 467         if (!khd)
 468                 return -ENOMEM;
 469
 470         khd->kcqs = kmalloc_array_node(hctx->nr_ctx,
 471                                        sizeof(struct kyber_ctx_queue),
 472                                        GFP_KERNEL, hctx->numa_node);
 473         if (!khd->kcqs)
 474                 goto err_khd;
 475
 476         for (i = 0; i < hctx->nr_ctx; i++)
 477                 kyber_ctx_queue_init(&khd->kcqs[i]);
 478
 479         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
 480                 if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
 481                                       ilog2(8), GFP_KERNEL, hctx->numa_node)) {
 482                         while (--i >= 0)
 483                                 sbitmap_free(&khd->kcq_map[i]);
 484                         goto err_kcqs;
 485                 }
 486         }
 487
 488         spin_lock_init(&khd->lock);
 489
 490         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
 491                 INIT_LIST_HEAD(&khd->rqs[i]);
 492                 khd->domain_wait[i].sbq = NULL;
 493                 init_waitqueue_func_entry(&khd->domain_wait[i].wait,
 494                                           kyber_domain_wake);
 495                 khd->domain_wait[i].wait.private = hctx;
 496                 INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry);
 497                 atomic_set(&khd->wait_index[i], 0);
 498         }
 499
 500         khd->cur_domain = 0;
 501         khd->batching = 0;
 502
 503         hctx->sched_data = khd;
 504         kyber_depth_updated(hctx);
 505
 506         return 0;
 507
 508 err_kcqs:
 509         kfree(khd->kcqs);
 510 err_khd:
 511         kfree(khd);
 512         return -ENOMEM;
 513 }
 514
 515 static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
 516 {
 517         struct kyber_hctx_data *khd = hctx->sched_data;
 518         int i;
 519
 520         for (i = 0; i < KYBER_NUM_DOMAINS; i++)
 521                 sbitmap_free(&khd->kcq_map[i]);
 522         kfree(khd->kcqs);
 523         kfree(hctx->sched_data);
 524 }
 525
 526 static int rq_get_domain_token(struct request *rq)
 527 {
 528         return (long)rq->elv.priv[0];
 529 }
 530
 531 static void rq_set_domain_token(struct request *rq, int token)
 532 {
 533         rq->elv.priv[0] = (void *)(long)token;
 534 }
 535
 536 static void rq_clear_domain_token(struct kyber_queue_data *kqd,
 537                                   struct request *rq)
 538 {
 539         unsigned int sched_domain;
 540         int nr;
 541
 542         nr = rq_get_domain_token(rq);
 543         if (nr != -1) {
 544                 sched_domain = kyber_sched_domain(rq->cmd_flags);
 545                 sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,
 546                                     rq->mq_ctx->cpu);
 547         }
 548 }
 549
 550 static void kyber_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
 551 {
 552         /*
 553          * We use the scheduler tags as per-hardware queue queueing tokens.
 554          * Async requests can be limited at this stage.
 555          */
 556         if (!op_is_sync(op)) {
 557                 struct kyber_queue_data *kqd = data->q->elevator->elevator_data;
 558
 559                 data->shallow_depth = kqd->async_depth;
 560         }
 561 }
 562
 563 static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio,
 564                 unsigned int nr_segs)
 565 {
 566         struct kyber_hctx_data *khd = hctx->sched_data;
 567         struct blk_mq_ctx *ctx = blk_mq_get_ctx(hctx->queue);
 568         struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw[hctx->type]];
 569         unsigned int sched_domain = kyber_sched_domain(bio->bi_opf);
 570         struct list_head *rq_list = &kcq->rq_list[sched_domain];
 571         bool merged;
 572
 573         spin_lock(&kcq->lock);
 574         merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
 575         spin_unlock(&kcq->lock);
 576
 577         return merged;
 578 }
 579
 580 static void kyber_prepare_request(struct request *rq)
 581 {
 582         rq_set_domain_token(rq, -1);
 583 }
 584
 585 static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx,
 586                                   struct list_head *rq_list, bool at_head)
 587 {
 588         struct kyber_hctx_data *khd = hctx->sched_data;
 589         struct request *rq, *next;
 590
 591         list_for_each_entry_safe(rq, next, rq_list, queuelist) {
 592                 unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags);
 593                 struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw[hctx->type]];
 594                 struct list_head *head = &kcq->rq_list[sched_domain];
 595
 596                 spin_lock(&kcq->lock);
 597                 if (at_head)
 598                         list_move(&rq->queuelist, head);
 599                 else
 600                         list_move_tail(&rq->queuelist, head);
 601                 sbitmap_set_bit(&khd->kcq_map[sched_domain],
 602                                 rq->mq_ctx->index_hw[hctx->type]);
 603                 trace_block_rq_insert(rq);
 604                 spin_unlock(&kcq->lock);
 605         }
 606 }
 607
 608 static void kyber_finish_request(struct request *rq)
 609 {
 610         struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
 611
 612         rq_clear_domain_token(kqd, rq);
 613 }
 614
 615 static void add_latency_sample(struct kyber_cpu_latency *cpu_latency,
 616                                unsigned int sched_domain, unsigned int type,
 617                                u64 target, u64 latency)
 618 {
 619         unsigned int bucket;
 620         u64 divisor;
 621
 622         if (latency > 0) {
 623                 divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1);
 624                 bucket = min_t(unsigned int, div64_u64(latency - 1, divisor),
 625                                KYBER_LATENCY_BUCKETS - 1);
 626         } else {
 627                 bucket = 0;
 628         }
 629
 630         atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]);
 631 }
 632
 633 static void kyber_completed_request(struct request *rq, u64 now)
 634 {
 635         struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
 636         struct kyber_cpu_latency *cpu_latency;
 637         unsigned int sched_domain;
 638         u64 target;
 639
 640         sched_domain = kyber_sched_domain(rq->cmd_flags);
 641         if (sched_domain == KYBER_OTHER)
 642                 return;
 643
 644         cpu_latency = get_cpu_ptr(kqd->cpu_latency);
 645         target = kqd->latency_targets[sched_domain];
 646         add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY,
 647                            target, now - rq->start_time_ns);
 648         add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target,
 649                            now - rq->io_start_time_ns);
 650         put_cpu_ptr(kqd->cpu_latency);
 651
 652         timer_reduce(&kqd->timer, jiffies + HZ / 10);
 653 }
 654
 655 struct flush_kcq_data {
 656         struct kyber_hctx_data *khd;
 657         unsigned int sched_domain;
 658         struct list_head *list;
 659 };
 660
 661 static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data)
 662 {
 663         struct flush_kcq_data *flush_data = data;
 664         struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr];
 665
 666         spin_lock(&kcq->lock);
 667         list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain],
 668                               flush_data->list);
 669         sbitmap_clear_bit(sb, bitnr);
 670         spin_unlock(&kcq->lock);
 671
 672         return true;
 673 }
 674
 675 static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd,
 676                                   unsigned int sched_domain,
 677                                   struct list_head *list)
 678 {
 679         struct flush_kcq_data data = {
 680                 .khd = khd,
 681                 .sched_domain = sched_domain,
 682                 .list = list,
 683         };
 684
 685         sbitmap_for_each_set(&khd->kcq_map[sched_domain],
 686                              flush_busy_kcq, &data);
 687 }
 688
 689 static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags,
 690                              void *key)
 691 {
 692         struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private);
 693         struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait);
 694
 695         sbitmap_del_wait_queue(wait);
 696         blk_mq_run_hw_queue(hctx, true);
 697         return 1;
 698 }
 699
 700 static int kyber_get_domain_token(struct kyber_queue_data *kqd,
 701                                   struct kyber_hctx_data *khd,
 702                                   struct blk_mq_hw_ctx *hctx)
 703 {
 704         unsigned int sched_domain = khd->cur_domain;
 705         struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain];
 706         struct sbq_wait *wait = &khd->domain_wait[sched_domain];
 707         struct sbq_wait_state *ws;
 708         int nr;
 709
 710         nr = __sbitmap_queue_get(domain_tokens);
 711
 712         /*
 713          * If we failed to get a domain token, make sure the hardware queue is
 714          * run when one becomes available. Note that this is serialized on
 715          * khd->lock, but we still need to be careful about the waker.
 716          */
 717         if (nr < 0 && list_empty_careful(&wait->wait.entry)) {
 718                 ws = sbq_wait_ptr(domain_tokens,
 719                                   &khd->wait_index[sched_domain]);
 720                 khd->domain_ws[sched_domain] = ws;
 721                 sbitmap_add_wait_queue(domain_tokens, ws, wait);
 722
 723                 /*
 724                  * Try again in case a token was freed before we got on the wait
 725                  * queue.
 726                  */
 727                 nr = __sbitmap_queue_get(domain_tokens);
 728         }
 729
 730         /*
 731          * If we got a token while we were on the wait queue, remove ourselves
 732          * from the wait queue to ensure that all wake ups make forward
 733          * progress. It's possible that the waker already deleted the entry
 734          * between the !list_empty_careful() check and us grabbing the lock, but
 735          * list_del_init() is okay with that.
 736          */
 737         if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) {
 738                 ws = khd->domain_ws[sched_domain];
 739                 spin_lock_irq(&ws->wait.lock);
 740                 sbitmap_del_wait_queue(wait);
 741                 spin_unlock_irq(&ws->wait.lock);
 742         }
 743
 744         return nr;
 745 }
 746
 747 static struct request *
 748 kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
 749                           struct kyber_hctx_data *khd,
 750                           struct blk_mq_hw_ctx *hctx)
 751 {
 752         struct list_head *rqs;
 753         struct request *rq;
 754         int nr;
 755
 756         rqs = &khd->rqs[khd->cur_domain];
 757
 758         /*
 759          * If we already have a flushed request, then we just need to get a
 760          * token for it. Otherwise, if there are pending requests in the kcqs,
 761          * flush the kcqs, but only if we can get a token. If not, we should
 762          * leave the requests in the kcqs so that they can be merged. Note that
 763          * khd->lock serializes the flushes, so if we observed any bit set in
 764          * the kcq_map, we will always get a request.
 765          */
 766         rq = list_first_entry_or_null(rqs, struct request, queuelist);
 767         if (rq) {
 768                 nr = kyber_get_domain_token(kqd, khd, hctx);
 769                 if (nr >= 0) {
 770                         khd->batching++;
 771                         rq_set_domain_token(rq, nr);
 772                         list_del_init(&rq->queuelist);
 773                         return rq;
 774                 } else {
 775                         trace_kyber_throttled(kqd->q,
 776                                               kyber_domain_names[khd->cur_domain]);
 777                 }
 778         } else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) {
 779                 nr = kyber_get_domain_token(kqd, khd, hctx);
 780                 if (nr >= 0) {
 781                         kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs);
 782                         rq = list_first_entry(rqs, struct request, queuelist);
 783                         khd->batching++;
 784                         rq_set_domain_token(rq, nr);
 785                         list_del_init(&rq->queuelist);
 786                         return rq;
 787                 } else {
 788                         trace_kyber_throttled(kqd->q,
 789                                               kyber_domain_names[khd->cur_domain]);
 790                 }
 791         }
 792
 793         /* There were either no pending requests or no tokens. */
 794         return NULL;
 795 }
 796
 797 static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx)
 798 {
 799         struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
 800         struct kyber_hctx_data *khd = hctx->sched_data;
 801         struct request *rq;
 802         int i;
 803
 804         spin_lock(&khd->lock);
 805
 806         /*
 807          * First, if we are still entitled to batch, try to dispatch a request
 808          * from the batch.
 809          */
 810         if (khd->batching < kyber_batch_size[khd->cur_domain]) {
 811                 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
 812                 if (rq)
 813                         goto out;
 814         }
 815
 816         /*
 817          * Either,
 818          * 1. We were no longer entitled to a batch.
 819          * 2. The domain we were batching didn't have any requests.
 820          * 3. The domain we were batching was out of tokens.
 821          *
 822          * Start another batch. Note that this wraps back around to the original
 823          * domain if no other domains have requests or tokens.
 824          */
 825         khd->batching = 0;
 826         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
 827                 if (khd->cur_domain == KYBER_NUM_DOMAINS - 1)
 828                         khd->cur_domain = 0;
 829                 else
 830                         khd->cur_domain++;
 831
 832                 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
 833                 if (rq)
 834                         goto out;
 835         }
 836
 837         rq = NULL;
 838 out:
 839         spin_unlock(&khd->lock);
 840         return rq;
 841 }
 842
 843 static bool kyber_has_work(struct blk_mq_hw_ctx *hctx)
 844 {
 845         struct kyber_hctx_data *khd = hctx->sched_data;
 846         int i;
 847
 848         for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
 849                 if (!list_empty_careful(&khd->rqs[i]) ||
 850                     sbitmap_any_bit_set(&khd->kcq_map[i]))
 851                         return true;
 852         }
 853
 854         return false;
 855 }
 856
 857 #define KYBER_LAT_SHOW_STORE(domain, name)                              \
 858 static ssize_t kyber_##name##_lat_show(struct elevator_queue *e,        \
 859                                        char *page)                      \
 860 {                                                                       \
 861         struct kyber_queue_data *kqd = e->elevator_data;                \
 862                                                                         \
 863         return sprintf(page, "%llu\n", kqd->latency_targets[domain]);   \
 864 }                                                                       \
 865                                                                         \
 866 static ssize_t kyber_##name##_lat_store(struct elevator_queue *e,       \
 867                                         const char *page, size_t count) \
 868 {                                                                       \
 869         struct kyber_queue_data *kqd = e->elevator_data;                \
 870         unsigned long long nsec;                                        \
 871         int ret;                                                        \
 872                                                                         \
 873         ret = kstrtoull(page, 10, &nsec);                               \
 874         if (ret)                                                        \
 875                 return ret;                                             \
 876                                                                         \
 877         kqd->latency_targets[domain] = nsec;                            \
 878                                                                         \
 879         return count;                                                   \
 880 }
 881 KYBER_LAT_SHOW_STORE(KYBER_READ, read);
 882 KYBER_LAT_SHOW_STORE(KYBER_WRITE, write);
 883 #undef KYBER_LAT_SHOW_STORE
 884
 885 #define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store)
 886 static struct elv_fs_entry kyber_sched_attrs[] = {
 887         KYBER_LAT_ATTR(read),
 888         KYBER_LAT_ATTR(write),
 889         __ATTR_NULL
 890 };
 891 #undef KYBER_LAT_ATTR
 892
 893 #ifdef CONFIG_BLK_DEBUG_FS
 894 #define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name)                        \
 895 static int kyber_##name##_tokens_show(void *data, struct seq_file *m)   \
 896 {                                                                       \
 897         struct request_queue *q = data;                                 \
 898         struct kyber_queue_data *kqd = q->elevator->elevator_data;      \
 899                                                                         \
 900         sbitmap_queue_show(&kqd->domain_tokens[domain], m);             \
 901         return 0;                                                       \
 902 }                                                                       \
 903                                                                         \
 904 static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos)  \
 905         __acquires(&khd->lock)                                          \
 906 {                                                                       \
 907         struct blk_mq_hw_ctx *hctx = m->private;                        \
 908         struct kyber_hctx_data *khd = hctx->sched_data;                 \
 909                                                                         \
 910         spin_lock(&khd->lock);                                          \
 911         return seq_list_start(&khd->rqs[domain], *pos);                 \
 912 }                                                                       \
 913                                                                         \
 914 static void *kyber_##name##_rqs_next(struct seq_file *m, void *v,       \
 915                                      loff_t *pos)                       \
 916 {                                                                       \
 917         struct blk_mq_hw_ctx *hctx = m->private;                        \
 918         struct kyber_hctx_data *khd = hctx->sched_data;                 \
 919                                                                         \
 920         return seq_list_next(v, &khd->rqs[domain], pos);                \
 921 }                                                                       \
 922                                                                         \
 923 static void kyber_##name##_rqs_stop(struct seq_file *m, void *v)        \
 924         __releases(&khd->lock)                                          \
 925 {                                                                       \
 926         struct blk_mq_hw_ctx *hctx = m->private;                        \
 927         struct kyber_hctx_data *khd = hctx->sched_data;                 \
 928                                                                         \
 929         spin_unlock(&khd->lock);                                        \
 930 }                                                                       \
 931                                                                         \
 932 static const struct seq_operations kyber_##name##_rqs_seq_ops = {       \
 933         .start  = kyber_##name##_rqs_start,                             \
 934         .next   = kyber_##name##_rqs_next,                              \
 935         .stop   = kyber_##name##_rqs_stop,                              \
 936         .show   = blk_mq_debugfs_rq_show,                               \
 937 };                                                                      \
 938                                                                         \
 939 static int kyber_##name##_waiting_show(void *data, struct seq_file *m)  \
 940 {                                                                       \
 941         struct blk_mq_hw_ctx *hctx = data;                              \
 942         struct kyber_hctx_data *khd = hctx->sched_data;                 \
 943         wait_queue_entry_t *wait = &khd->domain_wait[domain].wait;      \
 944                                                                         \
 945         seq_printf(m, "%d\n", !list_empty_careful(&wait->entry));       \
 946         return 0;                                                       \
 947 }
 948 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
 949 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write)
 950 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard)
 951 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other)
 952 #undef KYBER_DEBUGFS_DOMAIN_ATTRS
 953
 954 static int kyber_async_depth_show(void *data, struct seq_file *m)
 955 {
 956         struct request_queue *q = data;
 957         struct kyber_queue_data *kqd = q->elevator->elevator_data;
 958
 959         seq_printf(m, "%u\n", kqd->async_depth);
 960         return 0;
 961 }
 962
 963 static int kyber_cur_domain_show(void *data, struct seq_file *m)
 964 {
 965         struct blk_mq_hw_ctx *hctx = data;
 966         struct kyber_hctx_data *khd = hctx->sched_data;
 967
 968         seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);
 969         return 0;
 970 }
 971
 972 static int kyber_batching_show(void *data, struct seq_file *m)
 973 {
 974         struct blk_mq_hw_ctx *hctx = data;
 975         struct kyber_hctx_data *khd = hctx->sched_data;
 976
 977         seq_printf(m, "%u\n", khd->batching);
 978         return 0;
 979 }
 980
 981 #define KYBER_QUEUE_DOMAIN_ATTRS(name)  \
 982         {#name "_tokens", 0400, kyber_##name##_tokens_show}
 983 static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = {
 984         KYBER_QUEUE_DOMAIN_ATTRS(read),
 985         KYBER_QUEUE_DOMAIN_ATTRS(write),
 986         KYBER_QUEUE_DOMAIN_ATTRS(discard),
 987         KYBER_QUEUE_DOMAIN_ATTRS(other),
 988         {"async_depth", 0400, kyber_async_depth_show},
 989         {},
 990 };
 991 #undef KYBER_QUEUE_DOMAIN_ATTRS
 992
 993 #define KYBER_HCTX_DOMAIN_ATTRS(name)                                   \
 994         {#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops},   \
 995         {#name "_waiting", 0400, kyber_##name##_waiting_show}
 996 static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = {
 997         KYBER_HCTX_DOMAIN_ATTRS(read),
 998         KYBER_HCTX_DOMAIN_ATTRS(write),
 999         KYBER_HCTX_DOMAIN_ATTRS(discard),
1000         KYBER_HCTX_DOMAIN_ATTRS(other),
1001         {"cur_domain", 0400, kyber_cur_domain_show},
1002         {"batching", 0400, kyber_batching_show},
1003         {},
1004 };
1005 #undef KYBER_HCTX_DOMAIN_ATTRS
1006 #endif
1007
1008 static struct elevator_type kyber_sched = {
1009         .ops = {
1010                 .init_sched = kyber_init_sched,
1011                 .exit_sched = kyber_exit_sched,
1012                 .init_hctx = kyber_init_hctx,
1013                 .exit_hctx = kyber_exit_hctx,
1014                 .limit_depth = kyber_limit_depth,
1015                 .bio_merge = kyber_bio_merge,
1016                 .prepare_request = kyber_prepare_request,
1017                 .insert_requests = kyber_insert_requests,
1018                 .finish_request = kyber_finish_request,
1019                 .requeue_request = kyber_finish_request,
1020                 .completed_request = kyber_completed_request,
1021                 .dispatch_request = kyber_dispatch_request,
1022                 .has_work = kyber_has_work,
1023                 .depth_updated = kyber_depth_updated,
1024         },
1025 #ifdef CONFIG_BLK_DEBUG_FS
1026         .queue_debugfs_attrs = kyber_queue_debugfs_attrs,
1027         .hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
1028 #endif
1029         .elevator_attrs = kyber_sched_attrs,
1030         .elevator_name = "kyber",
1031         .elevator_features = ELEVATOR_F_MQ_AWARE,
1032         .elevator_owner = THIS_MODULE,
1033 };
1034
1035 static int __init kyber_init(void)
1036 {
1037         return elv_register(&kyber_sched);
1038 }
1039
1040 static void __exit kyber_exit(void)
1041 {
1042         elv_unregister(&kyber_sched);
1043 }
1044
1045 module_init(kyber_init);
1046 module_exit(kyber_exit);
1047
1048 MODULE_AUTHOR("Omar Sandoval");
1049 MODULE_LICENSE("GPL");
1050 MODULE_DESCRIPTION("Kyber I/O scheduler");