OSCL-LXR linux-6.0.1/​block/​kyber-iosched.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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");

This page was automatically generated by the 2.1.0 LXR engine. The LXR team