1 // SPDX-License-Identifier: GPL-2.0
3 * The Kyber I/O scheduler. Controls latency by throttling queue depths using
6 * Copyright (C) 2017 Facebook
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>
16 #include <trace/events/block.h>
20 #include "blk-mq-debugfs.h"
21 #include "blk-mq-sched.h"
22 #include "blk-mq-tag.h"
24 #define CREATE_TRACE_POINTS
25 #include <trace/events/kyber.h>
28 * Scheduling domains: the device is divided into multiple domains based on the
39 static const char *kyber_domain_names[] = {
40 [KYBER_READ] = "READ",
41 [KYBER_WRITE] = "WRITE",
42 [KYBER_DISCARD] = "DISCARD",
43 [KYBER_OTHER] = "OTHER",
48 * In order to prevent starvation of synchronous requests by a flood of
49 * asynchronous requests, we reserve 25% of requests for synchronous
52 KYBER_ASYNC_PERCENT = 75,
56 * Maximum device-wide depth for each scheduling domain.
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.
62 static const unsigned int kyber_depth[] = {
70 * Default latency targets for each scheduling domain.
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,
79 * Batch size (number of requests we'll dispatch in a row) for each scheduling
82 static const unsigned int kyber_batch_size[] = {
90 * Requests latencies are recorded in a histogram with buckets defined relative
91 * to the target latency:
93 * <= 1/4 * target latency
94 * <= 1/2 * target latency
95 * <= 3/4 * 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
104 * The width of the latency histogram buckets is
105 * 1 / (1 << KYBER_LATENCY_SHIFT) * target latency.
107 KYBER_LATENCY_SHIFT = 2,
109 * The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency,
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,
118 * We measure both the total latency and the I/O latency (i.e., latency after
119 * submitting to the device).
126 static const char *kyber_latency_type_names[] = {
127 [KYBER_TOTAL_LATENCY] = "total",
128 [KYBER_IO_LATENCY] = "I/O",
132 * Per-cpu latency histograms: total latency and I/O latency for each scheduling
133 * domain except for KYBER_OTHER.
135 struct kyber_cpu_latency {
136 atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
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.
143 struct kyber_ctx_queue {
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.
149 struct list_head rq_list[KYBER_NUM_DOMAINS];
150 } ____cacheline_aligned_in_smp;
152 struct kyber_queue_data {
153 struct request_queue *q;
157 * Each scheduling domain has a limited number of in-flight requests
158 * device-wide, limited by these tokens.
160 struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS];
163 * Async request percentage, converted to per-word depth for
164 * sbitmap_get_shallow().
166 unsigned int async_depth;
168 struct kyber_cpu_latency __percpu *cpu_latency;
170 /* Timer for stats aggregation and adjusting domain tokens. */
171 struct timer_list timer;
173 unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
175 unsigned long latency_timeout[KYBER_OTHER];
177 int domain_p99[KYBER_OTHER];
179 /* Target latencies in nanoseconds. */
180 u64 latency_targets[KYBER_OTHER];
183 struct kyber_hctx_data {
185 struct list_head rqs[KYBER_NUM_DOMAINS];
186 unsigned int cur_domain;
187 unsigned int batching;
188 struct kyber_ctx_queue *kcqs;
189 struct sbitmap kcq_map[KYBER_NUM_DOMAINS];
190 struct sbq_wait domain_wait[KYBER_NUM_DOMAINS];
191 struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS];
192 atomic_t wait_index[KYBER_NUM_DOMAINS];
195 static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
198 static unsigned int kyber_sched_domain(unsigned int op)
200 switch (op & REQ_OP_MASK) {
206 return KYBER_DISCARD;
212 static void flush_latency_buckets(struct kyber_queue_data *kqd,
213 struct kyber_cpu_latency *cpu_latency,
214 unsigned int sched_domain, unsigned int type)
216 unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
217 atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];
220 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
221 buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);
225 * Calculate the histogram bucket with the given percentile rank, or -1 if there
226 * aren't enough samples yet.
228 static int calculate_percentile(struct kyber_queue_data *kqd,
229 unsigned int sched_domain, unsigned int type,
230 unsigned int percentile)
232 unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
233 unsigned int bucket, samples = 0, percentile_samples;
235 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
236 samples += buckets[bucket];
242 * We do the calculation once we have 500 samples or one second passes
243 * since the first sample was recorded, whichever comes first.
245 if (!kqd->latency_timeout[sched_domain])
246 kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL);
248 time_is_after_jiffies(kqd->latency_timeout[sched_domain])) {
251 kqd->latency_timeout[sched_domain] = 0;
253 percentile_samples = DIV_ROUND_UP(samples * percentile, 100);
254 for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) {
255 if (buckets[bucket] >= percentile_samples)
257 percentile_samples -= buckets[bucket];
259 memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));
261 trace_kyber_latency(kqd->dev, kyber_domain_names[sched_domain],
262 kyber_latency_type_names[type], percentile,
263 bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);
268 static void kyber_resize_domain(struct kyber_queue_data *kqd,
269 unsigned int sched_domain, unsigned int depth)
271 depth = clamp(depth, 1U, kyber_depth[sched_domain]);
272 if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
273 sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
274 trace_kyber_adjust(kqd->dev, kyber_domain_names[sched_domain],
279 static void kyber_timer_fn(struct timer_list *t)
281 struct kyber_queue_data *kqd = from_timer(kqd, t, timer);
282 unsigned int sched_domain;
286 /* Sum all of the per-cpu latency histograms. */
287 for_each_online_cpu(cpu) {
288 struct kyber_cpu_latency *cpu_latency;
290 cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu);
291 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
292 flush_latency_buckets(kqd, cpu_latency, sched_domain,
293 KYBER_TOTAL_LATENCY);
294 flush_latency_buckets(kqd, cpu_latency, sched_domain,
300 * Check if any domains have a high I/O latency, which might indicate
301 * congestion in the device. Note that we use the p90; we don't want to
302 * be too sensitive to outliers here.
304 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
307 p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,
309 if (p90 >= KYBER_GOOD_BUCKETS)
314 * Adjust the scheduling domain depths. If we determined that there was
315 * congestion, we throttle all domains with good latencies. Either way,
316 * we ease up on throttling domains with bad latencies.
318 for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
319 unsigned int orig_depth, depth;
322 p99 = calculate_percentile(kqd, sched_domain,
323 KYBER_TOTAL_LATENCY, 99);
325 * This is kind of subtle: different domains will not
326 * necessarily have enough samples to calculate the latency
327 * percentiles during the same window, so we have to remember
328 * the p99 for the next time we observe congestion; once we do,
329 * we don't want to throttle again until we get more data, so we
334 p99 = kqd->domain_p99[sched_domain];
335 kqd->domain_p99[sched_domain] = -1;
336 } else if (p99 >= 0) {
337 kqd->domain_p99[sched_domain] = p99;
343 * If this domain has bad latency, throttle less. Otherwise,
344 * throttle more iff we determined that there is congestion.
346 * The new depth is scaled linearly with the p99 latency vs the
347 * latency target. E.g., if the p99 is 3/4 of the target, then
348 * we throttle down to 3/4 of the current depth, and if the p99
349 * is 2x the target, then we double the depth.
351 if (bad || p99 >= KYBER_GOOD_BUCKETS) {
352 orig_depth = kqd->domain_tokens[sched_domain].sb.depth;
353 depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT;
354 kyber_resize_domain(kqd, sched_domain, depth);
359 static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
361 struct kyber_queue_data *kqd;
365 kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
370 kqd->dev = disk_devt(q->disk);
372 kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
373 GFP_KERNEL | __GFP_ZERO);
374 if (!kqd->cpu_latency)
377 timer_setup(&kqd->timer, kyber_timer_fn, 0);
379 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
380 WARN_ON(!kyber_depth[i]);
381 WARN_ON(!kyber_batch_size[i]);
382 ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],
383 kyber_depth[i], -1, false,
384 GFP_KERNEL, q->node);
387 sbitmap_queue_free(&kqd->domain_tokens[i]);
392 for (i = 0; i < KYBER_OTHER; i++) {
393 kqd->domain_p99[i] = -1;
394 kqd->latency_targets[i] = kyber_latency_targets[i];
400 free_percpu(kqd->cpu_latency);
407 static int kyber_init_sched(struct request_queue *q, struct elevator_type *e)
409 struct kyber_queue_data *kqd;
410 struct elevator_queue *eq;
412 eq = elevator_alloc(q, e);
416 kqd = kyber_queue_data_alloc(q);
418 kobject_put(&eq->kobj);
422 blk_stat_enable_accounting(q);
424 eq->elevator_data = kqd;
430 static void kyber_exit_sched(struct elevator_queue *e)
432 struct kyber_queue_data *kqd = e->elevator_data;
435 del_timer_sync(&kqd->timer);
437 for (i = 0; i < KYBER_NUM_DOMAINS; i++)
438 sbitmap_queue_free(&kqd->domain_tokens[i]);
439 free_percpu(kqd->cpu_latency);
443 static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
447 spin_lock_init(&kcq->lock);
448 for (i = 0; i < KYBER_NUM_DOMAINS; i++)
449 INIT_LIST_HEAD(&kcq->rq_list[i]);
452 static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
454 struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
455 struct blk_mq_tags *tags = hctx->sched_tags;
456 unsigned int shift = tags->bitmap_tags->sb.shift;
458 kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
460 sbitmap_queue_min_shallow_depth(tags->bitmap_tags, kqd->async_depth);
463 static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
465 struct kyber_hctx_data *khd;
468 khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
472 khd->kcqs = kmalloc_array_node(hctx->nr_ctx,
473 sizeof(struct kyber_ctx_queue),
474 GFP_KERNEL, hctx->numa_node);
478 for (i = 0; i < hctx->nr_ctx; i++)
479 kyber_ctx_queue_init(&khd->kcqs[i]);
481 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
482 if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
483 ilog2(8), GFP_KERNEL, hctx->numa_node,
486 sbitmap_free(&khd->kcq_map[i]);
491 spin_lock_init(&khd->lock);
493 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
494 INIT_LIST_HEAD(&khd->rqs[i]);
495 khd->domain_wait[i].sbq = NULL;
496 init_waitqueue_func_entry(&khd->domain_wait[i].wait,
498 khd->domain_wait[i].wait.private = hctx;
499 INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry);
500 atomic_set(&khd->wait_index[i], 0);
506 hctx->sched_data = khd;
507 kyber_depth_updated(hctx);
518 static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
520 struct kyber_hctx_data *khd = hctx->sched_data;
523 for (i = 0; i < KYBER_NUM_DOMAINS; i++)
524 sbitmap_free(&khd->kcq_map[i]);
526 kfree(hctx->sched_data);
529 static int rq_get_domain_token(struct request *rq)
531 return (long)rq->elv.priv[0];
534 static void rq_set_domain_token(struct request *rq, int token)
536 rq->elv.priv[0] = (void *)(long)token;
539 static void rq_clear_domain_token(struct kyber_queue_data *kqd,
542 unsigned int sched_domain;
545 nr = rq_get_domain_token(rq);
547 sched_domain = kyber_sched_domain(rq->cmd_flags);
548 sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,
553 static void kyber_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
556 * We use the scheduler tags as per-hardware queue queueing tokens.
557 * Async requests can be limited at this stage.
559 if (!op_is_sync(op)) {
560 struct kyber_queue_data *kqd = data->q->elevator->elevator_data;
562 data->shallow_depth = kqd->async_depth;
566 static bool kyber_bio_merge(struct request_queue *q, struct bio *bio,
567 unsigned int nr_segs)
569 struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
570 struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
571 struct kyber_hctx_data *khd = hctx->sched_data;
572 struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw[hctx->type]];
573 unsigned int sched_domain = kyber_sched_domain(bio->bi_opf);
574 struct list_head *rq_list = &kcq->rq_list[sched_domain];
577 spin_lock(&kcq->lock);
578 merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
579 spin_unlock(&kcq->lock);
584 static void kyber_prepare_request(struct request *rq)
586 rq_set_domain_token(rq, -1);
589 static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx,
590 struct list_head *rq_list, bool at_head)
592 struct kyber_hctx_data *khd = hctx->sched_data;
593 struct request *rq, *next;
595 list_for_each_entry_safe(rq, next, rq_list, queuelist) {
596 unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags);
597 struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw[hctx->type]];
598 struct list_head *head = &kcq->rq_list[sched_domain];
600 spin_lock(&kcq->lock);
601 trace_block_rq_insert(rq);
603 list_move(&rq->queuelist, head);
605 list_move_tail(&rq->queuelist, head);
606 sbitmap_set_bit(&khd->kcq_map[sched_domain],
607 rq->mq_ctx->index_hw[hctx->type]);
608 spin_unlock(&kcq->lock);
612 static void kyber_finish_request(struct request *rq)
614 struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
616 rq_clear_domain_token(kqd, rq);
619 static void add_latency_sample(struct kyber_cpu_latency *cpu_latency,
620 unsigned int sched_domain, unsigned int type,
621 u64 target, u64 latency)
627 divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1);
628 bucket = min_t(unsigned int, div64_u64(latency - 1, divisor),
629 KYBER_LATENCY_BUCKETS - 1);
634 atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]);
637 static void kyber_completed_request(struct request *rq, u64 now)
639 struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
640 struct kyber_cpu_latency *cpu_latency;
641 unsigned int sched_domain;
644 sched_domain = kyber_sched_domain(rq->cmd_flags);
645 if (sched_domain == KYBER_OTHER)
648 cpu_latency = get_cpu_ptr(kqd->cpu_latency);
649 target = kqd->latency_targets[sched_domain];
650 add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY,
651 target, now - rq->start_time_ns);
652 add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target,
653 now - rq->io_start_time_ns);
654 put_cpu_ptr(kqd->cpu_latency);
656 timer_reduce(&kqd->timer, jiffies + HZ / 10);
659 struct flush_kcq_data {
660 struct kyber_hctx_data *khd;
661 unsigned int sched_domain;
662 struct list_head *list;
665 static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data)
667 struct flush_kcq_data *flush_data = data;
668 struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr];
670 spin_lock(&kcq->lock);
671 list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain],
673 sbitmap_clear_bit(sb, bitnr);
674 spin_unlock(&kcq->lock);
679 static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd,
680 unsigned int sched_domain,
681 struct list_head *list)
683 struct flush_kcq_data data = {
685 .sched_domain = sched_domain,
689 sbitmap_for_each_set(&khd->kcq_map[sched_domain],
690 flush_busy_kcq, &data);
693 static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags,
696 struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private);
697 struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait);
699 sbitmap_del_wait_queue(wait);
700 blk_mq_run_hw_queue(hctx, true);
704 static int kyber_get_domain_token(struct kyber_queue_data *kqd,
705 struct kyber_hctx_data *khd,
706 struct blk_mq_hw_ctx *hctx)
708 unsigned int sched_domain = khd->cur_domain;
709 struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain];
710 struct sbq_wait *wait = &khd->domain_wait[sched_domain];
711 struct sbq_wait_state *ws;
714 nr = __sbitmap_queue_get(domain_tokens);
717 * If we failed to get a domain token, make sure the hardware queue is
718 * run when one becomes available. Note that this is serialized on
719 * khd->lock, but we still need to be careful about the waker.
721 if (nr < 0 && list_empty_careful(&wait->wait.entry)) {
722 ws = sbq_wait_ptr(domain_tokens,
723 &khd->wait_index[sched_domain]);
724 khd->domain_ws[sched_domain] = ws;
725 sbitmap_add_wait_queue(domain_tokens, ws, wait);
728 * Try again in case a token was freed before we got on the wait
731 nr = __sbitmap_queue_get(domain_tokens);
735 * If we got a token while we were on the wait queue, remove ourselves
736 * from the wait queue to ensure that all wake ups make forward
737 * progress. It's possible that the waker already deleted the entry
738 * between the !list_empty_careful() check and us grabbing the lock, but
739 * list_del_init() is okay with that.
741 if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) {
742 ws = khd->domain_ws[sched_domain];
743 spin_lock_irq(&ws->wait.lock);
744 sbitmap_del_wait_queue(wait);
745 spin_unlock_irq(&ws->wait.lock);
751 static struct request *
752 kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
753 struct kyber_hctx_data *khd,
754 struct blk_mq_hw_ctx *hctx)
756 struct list_head *rqs;
760 rqs = &khd->rqs[khd->cur_domain];
763 * If we already have a flushed request, then we just need to get a
764 * token for it. Otherwise, if there are pending requests in the kcqs,
765 * flush the kcqs, but only if we can get a token. If not, we should
766 * leave the requests in the kcqs so that they can be merged. Note that
767 * khd->lock serializes the flushes, so if we observed any bit set in
768 * the kcq_map, we will always get a request.
770 rq = list_first_entry_or_null(rqs, struct request, queuelist);
772 nr = kyber_get_domain_token(kqd, khd, hctx);
775 rq_set_domain_token(rq, nr);
776 list_del_init(&rq->queuelist);
779 trace_kyber_throttled(kqd->dev,
780 kyber_domain_names[khd->cur_domain]);
782 } else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) {
783 nr = kyber_get_domain_token(kqd, khd, hctx);
785 kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs);
786 rq = list_first_entry(rqs, struct request, queuelist);
788 rq_set_domain_token(rq, nr);
789 list_del_init(&rq->queuelist);
792 trace_kyber_throttled(kqd->dev,
793 kyber_domain_names[khd->cur_domain]);
797 /* There were either no pending requests or no tokens. */
801 static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx)
803 struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
804 struct kyber_hctx_data *khd = hctx->sched_data;
808 spin_lock(&khd->lock);
811 * First, if we are still entitled to batch, try to dispatch a request
814 if (khd->batching < kyber_batch_size[khd->cur_domain]) {
815 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
822 * 1. We were no longer entitled to a batch.
823 * 2. The domain we were batching didn't have any requests.
824 * 3. The domain we were batching was out of tokens.
826 * Start another batch. Note that this wraps back around to the original
827 * domain if no other domains have requests or tokens.
830 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
831 if (khd->cur_domain == KYBER_NUM_DOMAINS - 1)
836 rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
843 spin_unlock(&khd->lock);
847 static bool kyber_has_work(struct blk_mq_hw_ctx *hctx)
849 struct kyber_hctx_data *khd = hctx->sched_data;
852 for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
853 if (!list_empty_careful(&khd->rqs[i]) ||
854 sbitmap_any_bit_set(&khd->kcq_map[i]))
861 #define KYBER_LAT_SHOW_STORE(domain, name) \
862 static ssize_t kyber_##name##_lat_show(struct elevator_queue *e, \
865 struct kyber_queue_data *kqd = e->elevator_data; \
867 return sprintf(page, "%llu\n", kqd->latency_targets[domain]); \
870 static ssize_t kyber_##name##_lat_store(struct elevator_queue *e, \
871 const char *page, size_t count) \
873 struct kyber_queue_data *kqd = e->elevator_data; \
874 unsigned long long nsec; \
877 ret = kstrtoull(page, 10, &nsec); \
881 kqd->latency_targets[domain] = nsec; \
885 KYBER_LAT_SHOW_STORE(KYBER_READ, read);
886 KYBER_LAT_SHOW_STORE(KYBER_WRITE, write);
887 #undef KYBER_LAT_SHOW_STORE
889 #define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store)
890 static struct elv_fs_entry kyber_sched_attrs[] = {
891 KYBER_LAT_ATTR(read),
892 KYBER_LAT_ATTR(write),
895 #undef KYBER_LAT_ATTR
897 #ifdef CONFIG_BLK_DEBUG_FS
898 #define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name) \
899 static int kyber_##name##_tokens_show(void *data, struct seq_file *m) \
901 struct request_queue *q = data; \
902 struct kyber_queue_data *kqd = q->elevator->elevator_data; \
904 sbitmap_queue_show(&kqd->domain_tokens[domain], m); \
908 static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos) \
909 __acquires(&khd->lock) \
911 struct blk_mq_hw_ctx *hctx = m->private; \
912 struct kyber_hctx_data *khd = hctx->sched_data; \
914 spin_lock(&khd->lock); \
915 return seq_list_start(&khd->rqs[domain], *pos); \
918 static void *kyber_##name##_rqs_next(struct seq_file *m, void *v, \
921 struct blk_mq_hw_ctx *hctx = m->private; \
922 struct kyber_hctx_data *khd = hctx->sched_data; \
924 return seq_list_next(v, &khd->rqs[domain], pos); \
927 static void kyber_##name##_rqs_stop(struct seq_file *m, void *v) \
928 __releases(&khd->lock) \
930 struct blk_mq_hw_ctx *hctx = m->private; \
931 struct kyber_hctx_data *khd = hctx->sched_data; \
933 spin_unlock(&khd->lock); \
936 static const struct seq_operations kyber_##name##_rqs_seq_ops = { \
937 .start = kyber_##name##_rqs_start, \
938 .next = kyber_##name##_rqs_next, \
939 .stop = kyber_##name##_rqs_stop, \
940 .show = blk_mq_debugfs_rq_show, \
943 static int kyber_##name##_waiting_show(void *data, struct seq_file *m) \
945 struct blk_mq_hw_ctx *hctx = data; \
946 struct kyber_hctx_data *khd = hctx->sched_data; \
947 wait_queue_entry_t *wait = &khd->domain_wait[domain].wait; \
949 seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \
952 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
953 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write)
954 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard)
955 KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other)
956 #undef KYBER_DEBUGFS_DOMAIN_ATTRS
958 static int kyber_async_depth_show(void *data, struct seq_file *m)
960 struct request_queue *q = data;
961 struct kyber_queue_data *kqd = q->elevator->elevator_data;
963 seq_printf(m, "%u\n", kqd->async_depth);
967 static int kyber_cur_domain_show(void *data, struct seq_file *m)
969 struct blk_mq_hw_ctx *hctx = data;
970 struct kyber_hctx_data *khd = hctx->sched_data;
972 seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);
976 static int kyber_batching_show(void *data, struct seq_file *m)
978 struct blk_mq_hw_ctx *hctx = data;
979 struct kyber_hctx_data *khd = hctx->sched_data;
981 seq_printf(m, "%u\n", khd->batching);
985 #define KYBER_QUEUE_DOMAIN_ATTRS(name) \
986 {#name "_tokens", 0400, kyber_##name##_tokens_show}
987 static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = {
988 KYBER_QUEUE_DOMAIN_ATTRS(read),
989 KYBER_QUEUE_DOMAIN_ATTRS(write),
990 KYBER_QUEUE_DOMAIN_ATTRS(discard),
991 KYBER_QUEUE_DOMAIN_ATTRS(other),
992 {"async_depth", 0400, kyber_async_depth_show},
995 #undef KYBER_QUEUE_DOMAIN_ATTRS
997 #define KYBER_HCTX_DOMAIN_ATTRS(name) \
998 {#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops}, \
999 {#name "_waiting", 0400, kyber_##name##_waiting_show}
1000 static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = {
1001 KYBER_HCTX_DOMAIN_ATTRS(read),
1002 KYBER_HCTX_DOMAIN_ATTRS(write),
1003 KYBER_HCTX_DOMAIN_ATTRS(discard),
1004 KYBER_HCTX_DOMAIN_ATTRS(other),
1005 {"cur_domain", 0400, kyber_cur_domain_show},
1006 {"batching", 0400, kyber_batching_show},
1009 #undef KYBER_HCTX_DOMAIN_ATTRS
1012 static struct elevator_type kyber_sched = {
1014 .init_sched = kyber_init_sched,
1015 .exit_sched = kyber_exit_sched,
1016 .init_hctx = kyber_init_hctx,
1017 .exit_hctx = kyber_exit_hctx,
1018 .limit_depth = kyber_limit_depth,
1019 .bio_merge = kyber_bio_merge,
1020 .prepare_request = kyber_prepare_request,
1021 .insert_requests = kyber_insert_requests,
1022 .finish_request = kyber_finish_request,
1023 .requeue_request = kyber_finish_request,
1024 .completed_request = kyber_completed_request,
1025 .dispatch_request = kyber_dispatch_request,
1026 .has_work = kyber_has_work,
1027 .depth_updated = kyber_depth_updated,
1029 #ifdef CONFIG_BLK_DEBUG_FS
1030 .queue_debugfs_attrs = kyber_queue_debugfs_attrs,
1031 .hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
1033 .elevator_attrs = kyber_sched_attrs,
1034 .elevator_name = "kyber",
1035 .elevator_features = ELEVATOR_F_MQ_AWARE,
1036 .elevator_owner = THIS_MODULE,
1039 static int __init kyber_init(void)
1041 return elv_register(&kyber_sched);
1044 static void __exit kyber_exit(void)
1046 elv_unregister(&kyber_sched);
1049 module_init(kyber_init);
1050 module_exit(kyber_exit);
1052 MODULE_AUTHOR("Omar Sandoval");
1053 MODULE_LICENSE("GPL");
1054 MODULE_DESCRIPTION("Kyber I/O scheduler");