linux/block/blk-stat.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Block stat tracking code
   4 *
   5 * Copyright (C) 2016 Jens Axboe
   6 */
   7#include <linux/kernel.h>
   8#include <linux/rculist.h>
   9#include <linux/blk-mq.h>
  10
  11#include "blk-stat.h"
  12#include "blk-mq.h"
  13#include "blk.h"
  14
  15struct blk_queue_stats {
  16        struct list_head callbacks;
  17        spinlock_t lock;
  18        bool enable_accounting;
  19};
  20
  21void blk_rq_stat_init(struct blk_rq_stat *stat)
  22{
  23        stat->min = -1ULL;
  24        stat->max = stat->nr_samples = stat->mean = 0;
  25        stat->batch = 0;
  26}
  27
  28/* src is a per-cpu stat, mean isn't initialized */
  29void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
  30{
  31        if (!src->nr_samples)
  32                return;
  33
  34        dst->min = min(dst->min, src->min);
  35        dst->max = max(dst->max, src->max);
  36
  37        dst->mean = div_u64(src->batch + dst->mean * dst->nr_samples,
  38                                dst->nr_samples + src->nr_samples);
  39
  40        dst->nr_samples += src->nr_samples;
  41}
  42
  43void blk_rq_stat_add(struct blk_rq_stat *stat, u64 value)
  44{
  45        stat->min = min(stat->min, value);
  46        stat->max = max(stat->max, value);
  47        stat->batch += value;
  48        stat->nr_samples++;
  49}
  50
  51void blk_stat_add(struct request *rq, u64 now)
  52{
  53        struct request_queue *q = rq->q;
  54        struct blk_stat_callback *cb;
  55        struct blk_rq_stat *stat;
  56        int bucket, cpu;
  57        u64 value;
  58
  59        value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
  60
  61        blk_throtl_stat_add(rq, value);
  62
  63        rcu_read_lock();
  64        cpu = get_cpu();
  65        list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
  66                if (!blk_stat_is_active(cb))
  67                        continue;
  68
  69                bucket = cb->bucket_fn(rq);
  70                if (bucket < 0)
  71                        continue;
  72
  73                stat = &per_cpu_ptr(cb->cpu_stat, cpu)[bucket];
  74                blk_rq_stat_add(stat, value);
  75        }
  76        put_cpu();
  77        rcu_read_unlock();
  78}
  79
  80static void blk_stat_timer_fn(struct timer_list *t)
  81{
  82        struct blk_stat_callback *cb = from_timer(cb, t, timer);
  83        unsigned int bucket;
  84        int cpu;
  85
  86        for (bucket = 0; bucket < cb->buckets; bucket++)
  87                blk_rq_stat_init(&cb->stat[bucket]);
  88
  89        for_each_online_cpu(cpu) {
  90                struct blk_rq_stat *cpu_stat;
  91
  92                cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
  93                for (bucket = 0; bucket < cb->buckets; bucket++) {
  94                        blk_rq_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
  95                        blk_rq_stat_init(&cpu_stat[bucket]);
  96                }
  97        }
  98
  99        cb->timer_fn(cb);
 100}
 101
 102struct blk_stat_callback *
 103blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 104                        int (*bucket_fn)(const struct request *),
 105                        unsigned int buckets, void *data)
 106{
 107        struct blk_stat_callback *cb;
 108
 109        cb = kmalloc(sizeof(*cb), GFP_KERNEL);
 110        if (!cb)
 111                return NULL;
 112
 113        cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
 114                                 GFP_KERNEL);
 115        if (!cb->stat) {
 116                kfree(cb);
 117                return NULL;
 118        }
 119        cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
 120                                      __alignof__(struct blk_rq_stat));
 121        if (!cb->cpu_stat) {
 122                kfree(cb->stat);
 123                kfree(cb);
 124                return NULL;
 125        }
 126
 127        cb->timer_fn = timer_fn;
 128        cb->bucket_fn = bucket_fn;
 129        cb->data = data;
 130        cb->buckets = buckets;
 131        timer_setup(&cb->timer, blk_stat_timer_fn, 0);
 132
 133        return cb;
 134}
 135
 136void blk_stat_add_callback(struct request_queue *q,
 137                           struct blk_stat_callback *cb)
 138{
 139        unsigned int bucket;
 140        unsigned long flags;
 141        int cpu;
 142
 143        for_each_possible_cpu(cpu) {
 144                struct blk_rq_stat *cpu_stat;
 145
 146                cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
 147                for (bucket = 0; bucket < cb->buckets; bucket++)
 148                        blk_rq_stat_init(&cpu_stat[bucket]);
 149        }
 150
 151        spin_lock_irqsave(&q->stats->lock, flags);
 152        list_add_tail_rcu(&cb->list, &q->stats->callbacks);
 153        blk_queue_flag_set(QUEUE_FLAG_STATS, q);
 154        spin_unlock_irqrestore(&q->stats->lock, flags);
 155}
 156
 157void blk_stat_remove_callback(struct request_queue *q,
 158                              struct blk_stat_callback *cb)
 159{
 160        unsigned long flags;
 161
 162        spin_lock_irqsave(&q->stats->lock, flags);
 163        list_del_rcu(&cb->list);
 164        if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
 165                blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
 166        spin_unlock_irqrestore(&q->stats->lock, flags);
 167
 168        del_timer_sync(&cb->timer);
 169}
 170
 171static void blk_stat_free_callback_rcu(struct rcu_head *head)
 172{
 173        struct blk_stat_callback *cb;
 174
 175        cb = container_of(head, struct blk_stat_callback, rcu);
 176        free_percpu(cb->cpu_stat);
 177        kfree(cb->stat);
 178        kfree(cb);
 179}
 180
 181void blk_stat_free_callback(struct blk_stat_callback *cb)
 182{
 183        if (cb)
 184                call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
 185}
 186
 187void blk_stat_enable_accounting(struct request_queue *q)
 188{
 189        unsigned long flags;
 190
 191        spin_lock_irqsave(&q->stats->lock, flags);
 192        q->stats->enable_accounting = true;
 193        blk_queue_flag_set(QUEUE_FLAG_STATS, q);
 194        spin_unlock_irqrestore(&q->stats->lock, flags);
 195}
 196EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);
 197
 198struct blk_queue_stats *blk_alloc_queue_stats(void)
 199{
 200        struct blk_queue_stats *stats;
 201
 202        stats = kmalloc(sizeof(*stats), GFP_KERNEL);
 203        if (!stats)
 204                return NULL;
 205
 206        INIT_LIST_HEAD(&stats->callbacks);
 207        spin_lock_init(&stats->lock);
 208        stats->enable_accounting = false;
 209
 210        return stats;
 211}
 212
 213void blk_free_queue_stats(struct blk_queue_stats *stats)
 214{
 215        if (!stats)
 216                return;
 217
 218        WARN_ON(!list_empty(&stats->callbacks));
 219
 220        kfree(stats);
 221}
 222
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