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Diffstat (limited to '')
| -rw-r--r-- | block/kyber-iosched.c | 1056 |
1 files changed, 1056 insertions, 0 deletions
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c new file mode 100644 index 000000000..b05357bce --- /dev/null +++ b/block/kyber-iosched.c @@ -0,0 +1,1056 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * The Kyber I/O scheduler. Controls latency by throttling queue depths using + * scalable techniques. + * + * Copyright (C) 2017 Facebook + */ + +#include <linux/kernel.h> +#include <linux/blkdev.h> +#include <linux/blk-mq.h> +#include <linux/module.h> +#include <linux/sbitmap.h> + +#include <trace/events/block.h> + +#include "elevator.h" +#include "blk.h" +#include "blk-mq.h" +#include "blk-mq-debugfs.h" +#include "blk-mq-sched.h" +#include "blk-mq-tag.h" + +#define CREATE_TRACE_POINTS +#include <trace/events/kyber.h> + +/* + * Scheduling domains: the device is divided into multiple domains based on the + * request type. + */ +enum { + KYBER_READ, + KYBER_WRITE, + KYBER_DISCARD, + KYBER_OTHER, + KYBER_NUM_DOMAINS, +}; + +static const char *kyber_domain_names[] = { + [KYBER_READ] = "READ", + [KYBER_WRITE] = "WRITE", + [KYBER_DISCARD] = "DISCARD", + [KYBER_OTHER] = "OTHER", +}; + +enum { + /* + * In order to prevent starvation of synchronous requests by a flood of + * asynchronous requests, we reserve 25% of requests for synchronous + * operations. + */ + KYBER_ASYNC_PERCENT = 75, +}; + +/* + * Maximum device-wide depth for each scheduling domain. + * + * Even for fast devices with lots of tags like NVMe, you can saturate the + * device with only a fraction of the maximum possible queue depth. So, we cap + * these to a reasonable value. + */ +static const unsigned int kyber_depth[] = { + [KYBER_READ] = 256, + [KYBER_WRITE] = 128, + [KYBER_DISCARD] = 64, + [KYBER_OTHER] = 16, +}; + +/* + * Default latency targets for each scheduling domain. + */ +static const u64 kyber_latency_targets[] = { + [KYBER_READ] = 2ULL * NSEC_PER_MSEC, + [KYBER_WRITE] = 10ULL * NSEC_PER_MSEC, + [KYBER_DISCARD] = 5ULL * NSEC_PER_SEC, +}; + +/* + * Batch size (number of requests we'll dispatch in a row) for each scheduling + * domain. + */ +static const unsigned int kyber_batch_size[] = { + [KYBER_READ] = 16, + [KYBER_WRITE] = 8, + [KYBER_DISCARD] = 1, + [KYBER_OTHER] = 1, +}; + +/* + * Requests latencies are recorded in a histogram with buckets defined relative + * to the target latency: + * + * <= 1/4 * target latency + * <= 1/2 * target latency + * <= 3/4 * target latency + * <= target latency + * <= 1 1/4 * target latency + * <= 1 1/2 * target latency + * <= 1 3/4 * target latency + * > 1 3/4 * target latency + */ +enum { + /* + * The width of the latency histogram buckets is + * 1 / (1 << KYBER_LATENCY_SHIFT) * target latency. + */ + KYBER_LATENCY_SHIFT = 2, + /* + * The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency, + * thus, "good". + */ + KYBER_GOOD_BUCKETS = 1 << KYBER_LATENCY_SHIFT, + /* There are also (1 << KYBER_LATENCY_SHIFT) "bad" buckets. */ + KYBER_LATENCY_BUCKETS = 2 << KYBER_LATENCY_SHIFT, +}; + +/* + * We measure both the total latency and the I/O latency (i.e., latency after + * submitting to the device). + */ +enum { + KYBER_TOTAL_LATENCY, + KYBER_IO_LATENCY, +}; + +static const char *kyber_latency_type_names[] = { + [KYBER_TOTAL_LATENCY] = "total", + [KYBER_IO_LATENCY] = "I/O", +}; + +/* + * Per-cpu latency histograms: total latency and I/O latency for each scheduling + * domain except for KYBER_OTHER. + */ +struct kyber_cpu_latency { + atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS]; +}; + +/* + * There is a same mapping between ctx & hctx and kcq & khd, + * we use request->mq_ctx->index_hw to index the kcq in khd. + */ +struct kyber_ctx_queue { + /* + * Used to ensure operations on rq_list and kcq_map to be an atmoic one. + * Also protect the rqs on rq_list when merge. + */ + spinlock_t lock; + struct list_head rq_list[KYBER_NUM_DOMAINS]; +} ____cacheline_aligned_in_smp; + +struct kyber_queue_data { + struct request_queue *q; + dev_t dev; + + /* + * Each scheduling domain has a limited number of in-flight requests + * device-wide, limited by these tokens. + */ + struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS]; + + /* + * Async request percentage, converted to per-word depth for + * sbitmap_get_shallow(). + */ + unsigned int async_depth; + + struct kyber_cpu_latency __percpu *cpu_latency; + + /* Timer for stats aggregation and adjusting domain tokens. */ + struct timer_list timer; + + unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS]; + + unsigned long latency_timeout[KYBER_OTHER]; + + int domain_p99[KYBER_OTHER]; + + /* Target latencies in nanoseconds. */ + u64 latency_targets[KYBER_OTHER]; +}; + +struct kyber_hctx_data { + spinlock_t lock; + struct list_head rqs[KYBER_NUM_DOMAINS]; + unsigned int cur_domain; + unsigned int batching; + struct kyber_ctx_queue *kcqs; + struct sbitmap kcq_map[KYBER_NUM_DOMAINS]; + struct sbq_wait domain_wait[KYBER_NUM_DOMAINS]; + struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS]; + atomic_t wait_index[KYBER_NUM_DOMAINS]; +}; + +static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags, + void *key); + +static unsigned int kyber_sched_domain(blk_opf_t opf) +{ + switch (opf & REQ_OP_MASK) { + case REQ_OP_READ: + return KYBER_READ; + case REQ_OP_WRITE: + return KYBER_WRITE; + case REQ_OP_DISCARD: + return KYBER_DISCARD; + default: + return KYBER_OTHER; + } +} + +static void flush_latency_buckets(struct kyber_queue_data *kqd, + struct kyber_cpu_latency *cpu_latency, + unsigned int sched_domain, unsigned int type) +{ + unsigned int *buckets = kqd->latency_buckets[sched_domain][type]; + atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type]; + unsigned int bucket; + + for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++) + buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0); +} + +/* + * Calculate the histogram bucket with the given percentile rank, or -1 if there + * aren't enough samples yet. + */ +static int calculate_percentile(struct kyber_queue_data *kqd, + unsigned int sched_domain, unsigned int type, + unsigned int percentile) +{ + unsigned int *buckets = kqd->latency_buckets[sched_domain][type]; + unsigned int bucket, samples = 0, percentile_samples; + + for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++) + samples += buckets[bucket]; + + if (!samples) + return -1; + + /* + * We do the calculation once we have 500 samples or one second passes + * since the first sample was recorded, whichever comes first. + */ + if (!kqd->latency_timeout[sched_domain]) + kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL); + if (samples < 500 && + time_is_after_jiffies(kqd->latency_timeout[sched_domain])) { + return -1; + } + kqd->latency_timeout[sched_domain] = 0; + + percentile_samples = DIV_ROUND_UP(samples * percentile, 100); + for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) { + if (buckets[bucket] >= percentile_samples) + break; + percentile_samples -= buckets[bucket]; + } + memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type])); + + trace_kyber_latency(kqd->dev, kyber_domain_names[sched_domain], + kyber_latency_type_names[type], percentile, + bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples); + + return bucket; +} + +static void kyber_resize_domain(struct kyber_queue_data *kqd, + unsigned int sched_domain, unsigned int depth) +{ + depth = clamp(depth, 1U, kyber_depth[sched_domain]); + if (depth != kqd->domain_tokens[sched_domain].sb.depth) { + sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth); + trace_kyber_adjust(kqd->dev, kyber_domain_names[sched_domain], + depth); + } +} + +static void kyber_timer_fn(struct timer_list *t) +{ + struct kyber_queue_data *kqd = from_timer(kqd, t, timer); + unsigned int sched_domain; + int cpu; + bool bad = false; + + /* Sum all of the per-cpu latency histograms. */ + for_each_online_cpu(cpu) { + struct kyber_cpu_latency *cpu_latency; + + cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu); + for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) { + flush_latency_buckets(kqd, cpu_latency, sched_domain, + KYBER_TOTAL_LATENCY); + flush_latency_buckets(kqd, cpu_latency, sched_domain, + KYBER_IO_LATENCY); + } + } + + /* + * Check if any domains have a high I/O latency, which might indicate + * congestion in the device. Note that we use the p90; we don't want to + * be too sensitive to outliers here. + */ + for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) { + int p90; + + p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY, + 90); + if (p90 >= KYBER_GOOD_BUCKETS) + bad = true; + } + + /* + * Adjust the scheduling domain depths. If we determined that there was + * congestion, we throttle all domains with good latencies. Either way, + * we ease up on throttling domains with bad latencies. + */ + for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) { + unsigned int orig_depth, depth; + int p99; + + p99 = calculate_percentile(kqd, sched_domain, + KYBER_TOTAL_LATENCY, 99); + /* + * This is kind of subtle: different domains will not + * necessarily have enough samples to calculate the latency + * percentiles during the same window, so we have to remember + * the p99 for the next time we observe congestion; once we do, + * we don't want to throttle again until we get more data, so we + * reset it to -1. + */ + if (bad) { + if (p99 < 0) + p99 = kqd->domain_p99[sched_domain]; + kqd->domain_p99[sched_domain] = -1; + } else if (p99 >= 0) { + kqd->domain_p99[sched_domain] = p99; + } + if (p99 < 0) + continue; + + /* + * If this domain has bad latency, throttle less. Otherwise, + * throttle more iff we determined that there is congestion. + * + * The new depth is scaled linearly with the p99 latency vs the + * latency target. E.g., if the p99 is 3/4 of the target, then + * we throttle down to 3/4 of the current depth, and if the p99 + * is 2x the target, then we double the depth. + */ + if (bad || p99 >= KYBER_GOOD_BUCKETS) { + orig_depth = kqd->domain_tokens[sched_domain].sb.depth; + depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT; + kyber_resize_domain(kqd, sched_domain, depth); + } + } +} + +static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q) +{ + struct kyber_queue_data *kqd; + int ret = -ENOMEM; + int i; + + kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node); + if (!kqd) + goto err; + + kqd->q = q; + kqd->dev = disk_devt(q->disk); + + kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency, + GFP_KERNEL | __GFP_ZERO); + if (!kqd->cpu_latency) + goto err_kqd; + + timer_setup(&kqd->timer, kyber_timer_fn, 0); + + for (i = 0; i < KYBER_NUM_DOMAINS; i++) { + WARN_ON(!kyber_depth[i]); + WARN_ON(!kyber_batch_size[i]); + ret = sbitmap_queue_init_node(&kqd->domain_tokens[i], + kyber_depth[i], -1, false, + GFP_KERNEL, q->node); + if (ret) { + while (--i >= 0) + sbitmap_queue_free(&kqd->domain_tokens[i]); + goto err_buckets; + } + } + + for (i = 0; i < KYBER_OTHER; i++) { + kqd->domain_p99[i] = -1; + kqd->latency_targets[i] = kyber_latency_targets[i]; + } + + return kqd; + +err_buckets: + free_percpu(kqd->cpu_latency); +err_kqd: + kfree(kqd); +err: + return ERR_PTR(ret); +} + +static int kyber_init_sched(struct request_queue *q, struct elevator_type *e) +{ + struct kyber_queue_data *kqd; + struct elevator_queue *eq; + + eq = elevator_alloc(q, e); + if (!eq) + return -ENOMEM; + + kqd = kyber_queue_data_alloc(q); + if (IS_ERR(kqd)) { + kobject_put(&eq->kobj); + return PTR_ERR(kqd); + } + + blk_stat_enable_accounting(q); + + blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q); + + eq->elevator_data = kqd; + q->elevator = eq; + + return 0; +} + +static void kyber_exit_sched(struct elevator_queue *e) +{ + struct kyber_queue_data *kqd = e->elevator_data; + int i; + + del_timer_sync(&kqd->timer); + blk_stat_disable_accounting(kqd->q); + + for (i = 0; i < KYBER_NUM_DOMAINS; i++) + sbitmap_queue_free(&kqd->domain_tokens[i]); + free_percpu(kqd->cpu_latency); + kfree(kqd); +} + +static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq) +{ + unsigned int i; + + spin_lock_init(&kcq->lock); + for (i = 0; i < KYBER_NUM_DOMAINS; i++) + INIT_LIST_HEAD(&kcq->rq_list[i]); +} + +static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx) +{ + struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data; + struct blk_mq_tags *tags = hctx->sched_tags; + unsigned int shift = tags->bitmap_tags.sb.shift; + + kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U; + + sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth); +} + +static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) +{ + struct kyber_hctx_data *khd; + int i; + + khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node); + if (!khd) + return -ENOMEM; + + khd->kcqs = kmalloc_array_node(hctx->nr_ctx, + sizeof(struct kyber_ctx_queue), + GFP_KERNEL, hctx->numa_node); + if (!khd->kcqs) + goto err_khd; + + for (i = 0; i < hctx->nr_ctx; i++) + kyber_ctx_queue_init(&khd->kcqs[i]); + + for (i = 0; i < KYBER_NUM_DOMAINS; i++) { + if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx, + ilog2(8), GFP_KERNEL, hctx->numa_node, + false, false)) { + while (--i >= 0) + sbitmap_free(&khd->kcq_map[i]); + goto err_kcqs; + } + } + + spin_lock_init(&khd->lock); + + for (i = 0; i < KYBER_NUM_DOMAINS; i++) { + INIT_LIST_HEAD(&khd->rqs[i]); + khd->domain_wait[i].sbq = NULL; + init_waitqueue_func_entry(&khd->domain_wait[i].wait, + kyber_domain_wake); + khd->domain_wait[i].wait.private = hctx; + INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry); + atomic_set(&khd->wait_index[i], 0); + } + + khd->cur_domain = 0; + khd->batching = 0; + + hctx->sched_data = khd; + kyber_depth_updated(hctx); + + return 0; + +err_kcqs: + kfree(khd->kcqs); +err_khd: + kfree(khd); + return -ENOMEM; +} + +static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) +{ + struct kyber_hctx_data *khd = hctx->sched_data; + int i; + + for (i = 0; i < KYBER_NUM_DOMAINS; i++) + sbitmap_free(&khd->kcq_map[i]); + kfree(khd->kcqs); + kfree(hctx->sched_data); +} + +static int rq_get_domain_token(struct request *rq) +{ + return (long)rq->elv.priv[0]; +} + +static void rq_set_domain_token(struct request *rq, int token) +{ + rq->elv.priv[0] = (void *)(long)token; +} + +static void rq_clear_domain_token(struct kyber_queue_data *kqd, + struct request *rq) +{ + unsigned int sched_domain; + int nr; + + nr = rq_get_domain_token(rq); + if (nr != -1) { + sched_domain = kyber_sched_domain(rq->cmd_flags); + sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr, + rq->mq_ctx->cpu); + } +} + +static void kyber_limit_depth(blk_opf_t opf, struct blk_mq_alloc_data *data) +{ + /* + * We use the scheduler tags as per-hardware queue queueing tokens. + * Async requests can be limited at this stage. + */ + if (!op_is_sync(opf)) { + struct kyber_queue_data *kqd = data->q->elevator->elevator_data; + + data->shallow_depth = kqd->async_depth; + } +} + +static bool kyber_bio_merge(struct request_queue *q, struct bio *bio, + unsigned int nr_segs) +{ + struct blk_mq_ctx *ctx = blk_mq_get_ctx(q); + struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx); + struct kyber_hctx_data *khd = hctx->sched_data; + struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw[hctx->type]]; + unsigned int sched_domain = kyber_sched_domain(bio->bi_opf); + struct list_head *rq_list = &kcq->rq_list[sched_domain]; + bool merged; + + spin_lock(&kcq->lock); + merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs); + spin_unlock(&kcq->lock); + + return merged; +} + +static void kyber_prepare_request(struct request *rq) +{ + rq_set_domain_token(rq, -1); +} + +static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx, + struct list_head *rq_list, bool at_head) +{ + struct kyber_hctx_data *khd = hctx->sched_data; + struct request *rq, *next; + + list_for_each_entry_safe(rq, next, rq_list, queuelist) { + unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags); + struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw[hctx->type]]; + struct list_head *head = &kcq->rq_list[sched_domain]; + + spin_lock(&kcq->lock); + trace_block_rq_insert(rq); + if (at_head) + list_move(&rq->queuelist, head); + else + list_move_tail(&rq->queuelist, head); + sbitmap_set_bit(&khd->kcq_map[sched_domain], + rq->mq_ctx->index_hw[hctx->type]); + spin_unlock(&kcq->lock); + } +} + +static void kyber_finish_request(struct request *rq) +{ + struct kyber_queue_data *kqd = rq->q->elevator->elevator_data; + + rq_clear_domain_token(kqd, rq); +} + +static void add_latency_sample(struct kyber_cpu_latency *cpu_latency, + unsigned int sched_domain, unsigned int type, + u64 target, u64 latency) +{ + unsigned int bucket; + u64 divisor; + + if (latency > 0) { + divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1); + bucket = min_t(unsigned int, div64_u64(latency - 1, divisor), + KYBER_LATENCY_BUCKETS - 1); + } else { + bucket = 0; + } + + atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]); +} + +static void kyber_completed_request(struct request *rq, u64 now) +{ + struct kyber_queue_data *kqd = rq->q->elevator->elevator_data; + struct kyber_cpu_latency *cpu_latency; + unsigned int sched_domain; + u64 target; + + sched_domain = kyber_sched_domain(rq->cmd_flags); + if (sched_domain == KYBER_OTHER) + return; + + cpu_latency = get_cpu_ptr(kqd->cpu_latency); + target = kqd->latency_targets[sched_domain]; + add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY, + target, now - rq->start_time_ns); + add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target, + now - rq->io_start_time_ns); + put_cpu_ptr(kqd->cpu_latency); + + timer_reduce(&kqd->timer, jiffies + HZ / 10); +} + +struct flush_kcq_data { + struct kyber_hctx_data *khd; + unsigned int sched_domain; + struct list_head *list; +}; + +static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data) +{ + struct flush_kcq_data *flush_data = data; + struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr]; + + spin_lock(&kcq->lock); + list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain], + flush_data->list); + sbitmap_clear_bit(sb, bitnr); + spin_unlock(&kcq->lock); + + return true; +} + +static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd, + unsigned int sched_domain, + struct list_head *list) +{ + struct flush_kcq_data data = { + .khd = khd, + .sched_domain = sched_domain, + .list = list, + }; + + sbitmap_for_each_set(&khd->kcq_map[sched_domain], + flush_busy_kcq, &data); +} + +static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags, + void *key) +{ + struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private); + struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait); + + sbitmap_del_wait_queue(wait); + blk_mq_run_hw_queue(hctx, true); + return 1; +} + +static int kyber_get_domain_token(struct kyber_queue_data *kqd, + struct kyber_hctx_data *khd, + struct blk_mq_hw_ctx *hctx) +{ + unsigned int sched_domain = khd->cur_domain; + struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain]; + struct sbq_wait *wait = &khd->domain_wait[sched_domain]; + struct sbq_wait_state *ws; + int nr; + + nr = __sbitmap_queue_get(domain_tokens); + + /* + * If we failed to get a domain token, make sure the hardware queue is + * run when one becomes available. Note that this is serialized on + * khd->lock, but we still need to be careful about the waker. + */ + if (nr < 0 && list_empty_careful(&wait->wait.entry)) { + ws = sbq_wait_ptr(domain_tokens, + &khd->wait_index[sched_domain]); + khd->domain_ws[sched_domain] = ws; + sbitmap_add_wait_queue(domain_tokens, ws, wait); + + /* + * Try again in case a token was freed before we got on the wait + * queue. + */ + nr = __sbitmap_queue_get(domain_tokens); + } + + /* + * If we got a token while we were on the wait queue, remove ourselves + * from the wait queue to ensure that all wake ups make forward + * progress. It's possible that the waker already deleted the entry + * between the !list_empty_careful() check and us grabbing the lock, but + * list_del_init() is okay with that. + */ + if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) { + ws = khd->domain_ws[sched_domain]; + spin_lock_irq(&ws->wait.lock); + sbitmap_del_wait_queue(wait); + spin_unlock_irq(&ws->wait.lock); + } + + return nr; +} + +static struct request * +kyber_dispatch_cur_domain(struct kyber_queue_data *kqd, + struct kyber_hctx_data *khd, + struct blk_mq_hw_ctx *hctx) +{ + struct list_head *rqs; + struct request *rq; + int nr; + + rqs = &khd->rqs[khd->cur_domain]; + + /* + * If we already have a flushed request, then we just need to get a + * token for it. Otherwise, if there are pending requests in the kcqs, + * flush the kcqs, but only if we can get a token. If not, we should + * leave the requests in the kcqs so that they can be merged. Note that + * khd->lock serializes the flushes, so if we observed any bit set in + * the kcq_map, we will always get a request. + */ + rq = list_first_entry_or_null(rqs, struct request, queuelist); + if (rq) { + nr = kyber_get_domain_token(kqd, khd, hctx); + if (nr >= 0) { + khd->batching++; + rq_set_domain_token(rq, nr); + list_del_init(&rq->queuelist); + return rq; + } else { + trace_kyber_throttled(kqd->dev, + kyber_domain_names[khd->cur_domain]); + } + } else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) { + nr = kyber_get_domain_token(kqd, khd, hctx); + if (nr >= 0) { + kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs); + rq = list_first_entry(rqs, struct request, queuelist); + khd->batching++; + rq_set_domain_token(rq, nr); + list_del_init(&rq->queuelist); + return rq; + } else { + trace_kyber_throttled(kqd->dev, + kyber_domain_names[khd->cur_domain]); + } + } + + /* There were either no pending requests or no tokens. */ + return NULL; +} + +static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx) +{ + struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data; + struct kyber_hctx_data *khd = hctx->sched_data; + struct request *rq; + int i; + + spin_lock(&khd->lock); + + /* + * First, if we are still entitled to batch, try to dispatch a request + * from the batch. + */ + if (khd->batching < kyber_batch_size[khd->cur_domain]) { + rq = kyber_dispatch_cur_domain(kqd, khd, hctx); + if (rq) + goto out; + } + + /* + * Either, + * 1. We were no longer entitled to a batch. + * 2. The domain we were batching didn't have any requests. + * 3. The domain we were batching was out of tokens. + * + * Start another batch. Note that this wraps back around to the original + * domain if no other domains have requests or tokens. + */ + khd->batching = 0; + for (i = 0; i < KYBER_NUM_DOMAINS; i++) { + if (khd->cur_domain == KYBER_NUM_DOMAINS - 1) + khd->cur_domain = 0; + else + khd->cur_domain++; + + rq = kyber_dispatch_cur_domain(kqd, khd, hctx); + if (rq) + goto out; + } + + rq = NULL; +out: + spin_unlock(&khd->lock); + return rq; +} + +static bool kyber_has_work(struct blk_mq_hw_ctx *hctx) +{ + struct kyber_hctx_data *khd = hctx->sched_data; + int i; + + for (i = 0; i < KYBER_NUM_DOMAINS; i++) { + if (!list_empty_careful(&khd->rqs[i]) || + sbitmap_any_bit_set(&khd->kcq_map[i])) + return true; + } + + return false; +} + +#define KYBER_LAT_SHOW_STORE(domain, name) \ +static ssize_t kyber_##name##_lat_show(struct elevator_queue *e, \ + char *page) \ +{ \ + struct kyber_queue_data *kqd = e->elevator_data; \ + \ + return sprintf(page, "%llu\n", kqd->latency_targets[domain]); \ +} \ + \ +static ssize_t kyber_##name##_lat_store(struct elevator_queue *e, \ + const char *page, size_t count) \ +{ \ + struct kyber_queue_data *kqd = e->elevator_data; \ + unsigned long long nsec; \ + int ret; \ + \ + ret = kstrtoull(page, 10, &nsec); \ + if (ret) \ + return ret; \ + \ + kqd->latency_targets[domain] = nsec; \ + \ + return count; \ +} +KYBER_LAT_SHOW_STORE(KYBER_READ, read); +KYBER_LAT_SHOW_STORE(KYBER_WRITE, write); +#undef KYBER_LAT_SHOW_STORE + +#define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store) +static struct elv_fs_entry kyber_sched_attrs[] = { + KYBER_LAT_ATTR(read), + KYBER_LAT_ATTR(write), + __ATTR_NULL +}; +#undef KYBER_LAT_ATTR + +#ifdef CONFIG_BLK_DEBUG_FS +#define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name) \ +static int kyber_##name##_tokens_show(void *data, struct seq_file *m) \ +{ \ + struct request_queue *q = data; \ + struct kyber_queue_data *kqd = q->elevator->elevator_data; \ + \ + sbitmap_queue_show(&kqd->domain_tokens[domain], m); \ + return 0; \ +} \ + \ +static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos) \ + __acquires(&khd->lock) \ +{ \ + struct blk_mq_hw_ctx *hctx = m->private; \ + struct kyber_hctx_data *khd = hctx->sched_data; \ + \ + spin_lock(&khd->lock); \ + return seq_list_start(&khd->rqs[domain], *pos); \ +} \ + \ +static void *kyber_##name##_rqs_next(struct seq_file *m, void *v, \ + loff_t *pos) \ +{ \ + struct blk_mq_hw_ctx *hctx = m->private; \ + struct kyber_hctx_data *khd = hctx->sched_data; \ + \ + return seq_list_next(v, &khd->rqs[domain], pos); \ +} \ + \ +static void kyber_##name##_rqs_stop(struct seq_file *m, void *v) \ + __releases(&khd->lock) \ +{ \ + struct blk_mq_hw_ctx *hctx = m->private; \ + struct kyber_hctx_data *khd = hctx->sched_data; \ + \ + spin_unlock(&khd->lock); \ +} \ + \ +static const struct seq_operations kyber_##name##_rqs_seq_ops = { \ + .start = kyber_##name##_rqs_start, \ + .next = kyber_##name##_rqs_next, \ + .stop = kyber_##name##_rqs_stop, \ + .show = blk_mq_debugfs_rq_show, \ +}; \ + \ +static int kyber_##name##_waiting_show(void *data, struct seq_file *m) \ +{ \ + struct blk_mq_hw_ctx *hctx = data; \ + struct kyber_hctx_data *khd = hctx->sched_data; \ + wait_queue_entry_t *wait = &khd->domain_wait[domain].wait; \ + \ + seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \ + return 0; \ +} +KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read) +KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write) +KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard) +KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other) +#undef KYBER_DEBUGFS_DOMAIN_ATTRS + +static int kyber_async_depth_show(void *data, struct seq_file *m) +{ + struct request_queue *q = data; + struct kyber_queue_data *kqd = q->elevator->elevator_data; + + seq_printf(m, "%u\n", kqd->async_depth); + return 0; +} + +static int kyber_cur_domain_show(void *data, struct seq_file *m) +{ + struct blk_mq_hw_ctx *hctx = data; + struct kyber_hctx_data *khd = hctx->sched_data; + + seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]); + return 0; +} + +static int kyber_batching_show(void *data, struct seq_file *m) +{ + struct blk_mq_hw_ctx *hctx = data; + struct kyber_hctx_data *khd = hctx->sched_data; + + seq_printf(m, "%u\n", khd->batching); + return 0; +} + +#define KYBER_QUEUE_DOMAIN_ATTRS(name) \ + {#name "_tokens", 0400, kyber_##name##_tokens_show} +static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = { + KYBER_QUEUE_DOMAIN_ATTRS(read), + KYBER_QUEUE_DOMAIN_ATTRS(write), + KYBER_QUEUE_DOMAIN_ATTRS(discard), + KYBER_QUEUE_DOMAIN_ATTRS(other), + {"async_depth", 0400, kyber_async_depth_show}, + {}, +}; +#undef KYBER_QUEUE_DOMAIN_ATTRS + +#define KYBER_HCTX_DOMAIN_ATTRS(name) \ + {#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops}, \ + {#name "_waiting", 0400, kyber_##name##_waiting_show} +static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = { + KYBER_HCTX_DOMAIN_ATTRS(read), + KYBER_HCTX_DOMAIN_ATTRS(write), + KYBER_HCTX_DOMAIN_ATTRS(discard), + KYBER_HCTX_DOMAIN_ATTRS(other), + {"cur_domain", 0400, kyber_cur_domain_show}, + {"batching", 0400, kyber_batching_show}, + {}, +}; +#undef KYBER_HCTX_DOMAIN_ATTRS +#endif + +static struct elevator_type kyber_sched = { + .ops = { + .init_sched = kyber_init_sched, + .exit_sched = kyber_exit_sched, + .init_hctx = kyber_init_hctx, + .exit_hctx = kyber_exit_hctx, + .limit_depth = kyber_limit_depth, + .bio_merge = kyber_bio_merge, + .prepare_request = kyber_prepare_request, + .insert_requests = kyber_insert_requests, + .finish_request = kyber_finish_request, + .requeue_request = kyber_finish_request, + .completed_request = kyber_completed_request, + .dispatch_request = kyber_dispatch_request, + .has_work = kyber_has_work, + .depth_updated = kyber_depth_updated, + }, +#ifdef CONFIG_BLK_DEBUG_FS + .queue_debugfs_attrs = kyber_queue_debugfs_attrs, + .hctx_debugfs_attrs = kyber_hctx_debugfs_attrs, +#endif + .elevator_attrs = kyber_sched_attrs, + .elevator_name = "kyber", + .elevator_owner = THIS_MODULE, +}; + +static int __init kyber_init(void) +{ + return elv_register(&kyber_sched); +} + +static void __exit kyber_exit(void) +{ + elv_unregister(&kyber_sched); +} + +module_init(kyber_init); +module_exit(kyber_exit); + +MODULE_AUTHOR("Omar Sandoval"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Kyber I/O scheduler"); |