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![Pavel Begunkov](/assets/img/avatar_default.png)
blk_stat_add() calls {get,put}_cpu_ptr() in a loop, which entails overhead of disabling/enabling preemption. The loop is under RCU (i.e.short) anyway, so do get_cpu() in advance. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
216 lines
4.6 KiB
C
216 lines
4.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Block stat tracking code
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*
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* Copyright (C) 2016 Jens Axboe
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*/
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#include <linux/kernel.h>
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#include <linux/rculist.h>
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#include <linux/blk-mq.h>
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#include "blk-stat.h"
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#include "blk-mq.h"
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#include "blk.h"
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struct blk_queue_stats {
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struct list_head callbacks;
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spinlock_t lock;
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bool enable_accounting;
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};
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void blk_rq_stat_init(struct blk_rq_stat *stat)
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{
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stat->min = -1ULL;
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stat->max = stat->nr_samples = stat->mean = 0;
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stat->batch = 0;
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}
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/* src is a per-cpu stat, mean isn't initialized */
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void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
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{
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if (!src->nr_samples)
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return;
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dst->min = min(dst->min, src->min);
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dst->max = max(dst->max, src->max);
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dst->mean = div_u64(src->batch + dst->mean * dst->nr_samples,
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dst->nr_samples + src->nr_samples);
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dst->nr_samples += src->nr_samples;
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}
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void blk_rq_stat_add(struct blk_rq_stat *stat, u64 value)
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{
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stat->min = min(stat->min, value);
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stat->max = max(stat->max, value);
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stat->batch += value;
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stat->nr_samples++;
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}
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void blk_stat_add(struct request *rq, u64 now)
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{
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struct request_queue *q = rq->q;
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struct blk_stat_callback *cb;
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struct blk_rq_stat *stat;
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int bucket, cpu;
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u64 value;
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value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
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blk_throtl_stat_add(rq, value);
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rcu_read_lock();
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cpu = get_cpu();
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list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
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if (!blk_stat_is_active(cb))
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continue;
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bucket = cb->bucket_fn(rq);
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if (bucket < 0)
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continue;
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stat = &per_cpu_ptr(cb->cpu_stat, cpu)[bucket];
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blk_rq_stat_add(stat, value);
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}
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put_cpu();
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rcu_read_unlock();
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}
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static void blk_stat_timer_fn(struct timer_list *t)
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{
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struct blk_stat_callback *cb = from_timer(cb, t, timer);
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unsigned int bucket;
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int cpu;
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for (bucket = 0; bucket < cb->buckets; bucket++)
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blk_rq_stat_init(&cb->stat[bucket]);
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for_each_online_cpu(cpu) {
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struct blk_rq_stat *cpu_stat;
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cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
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for (bucket = 0; bucket < cb->buckets; bucket++) {
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blk_rq_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
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blk_rq_stat_init(&cpu_stat[bucket]);
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}
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}
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cb->timer_fn(cb);
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}
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struct blk_stat_callback *
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blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
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int (*bucket_fn)(const struct request *),
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unsigned int buckets, void *data)
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{
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struct blk_stat_callback *cb;
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cb = kmalloc(sizeof(*cb), GFP_KERNEL);
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if (!cb)
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return NULL;
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cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
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GFP_KERNEL);
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if (!cb->stat) {
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kfree(cb);
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return NULL;
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}
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cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
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__alignof__(struct blk_rq_stat));
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if (!cb->cpu_stat) {
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kfree(cb->stat);
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kfree(cb);
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return NULL;
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}
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cb->timer_fn = timer_fn;
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cb->bucket_fn = bucket_fn;
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cb->data = data;
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cb->buckets = buckets;
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timer_setup(&cb->timer, blk_stat_timer_fn, 0);
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return cb;
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}
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void blk_stat_add_callback(struct request_queue *q,
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struct blk_stat_callback *cb)
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{
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unsigned int bucket;
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int cpu;
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for_each_possible_cpu(cpu) {
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struct blk_rq_stat *cpu_stat;
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cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
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for (bucket = 0; bucket < cb->buckets; bucket++)
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blk_rq_stat_init(&cpu_stat[bucket]);
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}
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spin_lock(&q->stats->lock);
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list_add_tail_rcu(&cb->list, &q->stats->callbacks);
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blk_queue_flag_set(QUEUE_FLAG_STATS, q);
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spin_unlock(&q->stats->lock);
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}
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void blk_stat_remove_callback(struct request_queue *q,
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struct blk_stat_callback *cb)
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{
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spin_lock(&q->stats->lock);
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list_del_rcu(&cb->list);
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if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
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blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
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spin_unlock(&q->stats->lock);
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del_timer_sync(&cb->timer);
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}
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static void blk_stat_free_callback_rcu(struct rcu_head *head)
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{
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struct blk_stat_callback *cb;
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cb = container_of(head, struct blk_stat_callback, rcu);
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free_percpu(cb->cpu_stat);
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kfree(cb->stat);
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kfree(cb);
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}
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void blk_stat_free_callback(struct blk_stat_callback *cb)
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{
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if (cb)
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call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
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}
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void blk_stat_enable_accounting(struct request_queue *q)
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{
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spin_lock(&q->stats->lock);
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q->stats->enable_accounting = true;
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blk_queue_flag_set(QUEUE_FLAG_STATS, q);
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spin_unlock(&q->stats->lock);
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}
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EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);
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struct blk_queue_stats *blk_alloc_queue_stats(void)
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{
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struct blk_queue_stats *stats;
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stats = kmalloc(sizeof(*stats), GFP_KERNEL);
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if (!stats)
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return NULL;
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INIT_LIST_HEAD(&stats->callbacks);
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spin_lock_init(&stats->lock);
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stats->enable_accounting = false;
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return stats;
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}
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void blk_free_queue_stats(struct blk_queue_stats *stats)
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{
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if (!stats)
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return;
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WARN_ON(!list_empty(&stats->callbacks));
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kfree(stats);
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}
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