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;
  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         list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
  65                 if (!blk_stat_is_active(cb))
  66                         continue;
  67
  68                 bucket = cb->bucket_fn(rq);
  69                 if (bucket < 0)
  70                         continue;
  71
  72                 stat = &get_cpu_ptr(cb->cpu_stat)[bucket];
  73                 blk_rq_stat_add(stat, value);
  74                 put_cpu_ptr(cb->cpu_stat);
  75         }
  76         rcu_read_unlock();
  77 }
  78
  79 static void blk_stat_timer_fn(struct timer_list *t)
  80 {
  81         struct blk_stat_callback *cb = from_timer(cb, t, timer);
  82         unsigned int bucket;
  83         int cpu;
  84
  85         for (bucket = 0; bucket < cb->buckets; bucket++)
  86                 blk_rq_stat_init(&cb->stat[bucket]);
  87
  88         for_each_online_cpu(cpu) {
  89                 struct blk_rq_stat *cpu_stat;
  90
  91                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
  92                 for (bucket = 0; bucket < cb->buckets; bucket++) {
  93                         blk_rq_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
  94                         blk_rq_stat_init(&cpu_stat[bucket]);
  95                 }
  96         }
  97
  98         cb->timer_fn(cb);
  99 }
 100
 101 struct blk_stat_callback *
 102 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 103                         int (*bucket_fn)(const struct request *),
 104                         unsigned int buckets, void *data)
 105 {
 106         struct blk_stat_callback *cb;
 107
 108         cb = kmalloc(sizeof(*cb), GFP_KERNEL);
 109         if (!cb)
 110                 return NULL;
 111
 112         cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
 113                                  GFP_KERNEL);
 114         if (!cb->stat) {
 115                 kfree(cb);
 116                 return NULL;
 117         }
 118         cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
 119                                       __alignof__(struct blk_rq_stat));
 120         if (!cb->cpu_stat) {
 121                 kfree(cb->stat);
 122                 kfree(cb);
 123                 return NULL;
 124         }
 125
 126         cb->timer_fn = timer_fn;
 127         cb->bucket_fn = bucket_fn;
 128         cb->data = data;
 129         cb->buckets = buckets;
 130         timer_setup(&cb->timer, blk_stat_timer_fn, 0);
 131
 132         return cb;
 133 }
 134
 135 void blk_stat_add_callback(struct request_queue *q,
 136                            struct blk_stat_callback *cb)
 137 {
 138         unsigned int bucket;
 139         int cpu;
 140
 141         for_each_possible_cpu(cpu) {
 142                 struct blk_rq_stat *cpu_stat;
 143
 144                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
 145                 for (bucket = 0; bucket < cb->buckets; bucket++)
 146                         blk_rq_stat_init(&cpu_stat[bucket]);
 147         }
 148
 149         spin_lock(&q->stats->lock);
 150         list_add_tail_rcu(&cb->list, &q->stats->callbacks);
 151         blk_queue_flag_set(QUEUE_FLAG_STATS, q);
 152         spin_unlock(&q->stats->lock);
 153 }
 154
 155 void blk_stat_remove_callback(struct request_queue *q,
 156                               struct blk_stat_callback *cb)
 157 {
 158         spin_lock(&q->stats->lock);
 159         list_del_rcu(&cb->list);
 160         if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
 161                 blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
 162         spin_unlock(&q->stats->lock);
 163
 164         del_timer_sync(&cb->timer);
 165 }
 166
 167 static void blk_stat_free_callback_rcu(struct rcu_head *head)
 168 {
 169         struct blk_stat_callback *cb;
 170
 171         cb = container_of(head, struct blk_stat_callback, rcu);
 172         free_percpu(cb->cpu_stat);
 173         kfree(cb->stat);
 174         kfree(cb);
 175 }
 176
 177 void blk_stat_free_callback(struct blk_stat_callback *cb)
 178 {
 179         if (cb)
 180                 call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
 181 }
 182
 183 void blk_stat_enable_accounting(struct request_queue *q)
 184 {
 185         spin_lock(&q->stats->lock);
 186         q->stats->enable_accounting = true;
 187         blk_queue_flag_set(QUEUE_FLAG_STATS, q);
 188         spin_unlock(&q->stats->lock);
 189 }
 190 EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);
 191
 192 struct blk_queue_stats *blk_alloc_queue_stats(void)
 193 {
 194         struct blk_queue_stats *stats;
 195
 196         stats = kmalloc(sizeof(*stats), GFP_KERNEL);
 197         if (!stats)
 198                 return NULL;
 199
 200         INIT_LIST_HEAD(&stats->callbacks);
 201         spin_lock_init(&stats->lock);
 202         stats->enable_accounting = false;
 203
 204         return stats;
 205 }
 206
 207 void blk_free_queue_stats(struct blk_queue_stats *stats)
 208 {
 209         if (!stats)
 210                 return;
 211
 212         WARN_ON(!list_empty(&stats->callbacks));
 213
 214         kfree(stats);
 215 }