block/blk-stat.c

   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
  15 struct blk_queue_stats {
  16         struct list_head callbacks;
  17         spinlock_t lock;
  18         bool enable_accounting;
  19 };
  20
  21 void 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 */
  29 void 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
  43 void 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
  51 void 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
  80 static 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
 102 struct blk_stat_callback *
 103 blk_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
 136 void 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
 157 void 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
 171 static 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
 181 void 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
 187 void 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 }
 196 EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);
 197
 198 struct 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
 213 void 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 }