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
  10 #include "blk-stat.h"
  11 #include "blk-mq.h"
  12 #include "blk.h"
  13
  14 struct blk_queue_stats {
  15         struct list_head callbacks;
  16         spinlock_t lock;
  17         int accounting;
  18 };
  19
  20 void blk_rq_stat_init(struct blk_rq_stat *stat)
  21 {
  22         stat->min = -1ULL;
  23         stat->max = stat->nr_samples = stat->mean = 0;
  24         stat->batch = 0;
  25 }
  26
  27 /* src is a per-cpu stat, mean isn't initialized */
  28 void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
  29 {
  30         if (dst->nr_samples + src->nr_samples <= dst->nr_samples)
  31                 return;
  32
  33         dst->min = min(dst->min, src->min);
  34         dst->max = max(dst->max, src->max);
  35
  36         dst->mean = div_u64(src->batch + dst->mean * dst->nr_samples,
  37                                 dst->nr_samples + src->nr_samples);
  38
  39         dst->nr_samples += src->nr_samples;
  40 }
  41
  42 void blk_rq_stat_add(struct blk_rq_stat *stat, u64 value)
  43 {
  44         stat->min = min(stat->min, value);
  45         stat->max = max(stat->max, value);
  46         stat->batch += value;
  47         stat->nr_samples++;
  48 }
  49
  50 void blk_stat_add(struct request *rq, u64 now)
  51 {
  52         struct request_queue *q = rq->q;
  53         struct blk_stat_callback *cb;
  54         struct blk_rq_stat *stat;
  55         int bucket, cpu;
  56         u64 value;
  57
  58         value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
  59
  60         rcu_read_lock();
  61         cpu = get_cpu();
  62         list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
  63                 if (!blk_stat_is_active(cb))
  64                         continue;
  65
  66                 bucket = cb->bucket_fn(rq);
  67                 if (bucket < 0)
  68                         continue;
  69
  70                 stat = &per_cpu_ptr(cb->cpu_stat, cpu)[bucket];
  71                 blk_rq_stat_add(stat, value);
  72         }
  73         put_cpu();
  74         rcu_read_unlock();
  75 }
  76
  77 static void blk_stat_timer_fn(struct timer_list *t)
  78 {
  79         struct blk_stat_callback *cb = from_timer(cb, t, timer);
  80         unsigned int bucket;
  81         int cpu;
  82
  83         for (bucket = 0; bucket < cb->buckets; bucket++)
  84                 blk_rq_stat_init(&cb->stat[bucket]);
  85
  86         for_each_online_cpu(cpu) {
  87                 struct blk_rq_stat *cpu_stat;
  88
  89                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
  90                 for (bucket = 0; bucket < cb->buckets; bucket++) {
  91                         blk_rq_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
  92                         blk_rq_stat_init(&cpu_stat[bucket]);
  93                 }
  94         }
  95
  96         cb->timer_fn(cb);
  97 }
  98
  99 struct blk_stat_callback *
 100 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 101                         int (*bucket_fn)(const struct request *),
 102                         unsigned int buckets, void *data)
 103 {
 104         struct blk_stat_callback *cb;
 105
 106         cb = kmalloc(sizeof(*cb), GFP_KERNEL);
 107         if (!cb)
 108                 return NULL;
 109
 110         cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
 111                                  GFP_KERNEL);
 112         if (!cb->stat) {
 113                 kfree(cb);
 114                 return NULL;
 115         }
 116         cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
 117                                       __alignof__(struct blk_rq_stat));
 118         if (!cb->cpu_stat) {
 119                 kfree(cb->stat);
 120                 kfree(cb);
 121                 return NULL;
 122         }
 123
 124         cb->timer_fn = timer_fn;
 125         cb->bucket_fn = bucket_fn;
 126         cb->data = data;
 127         cb->buckets = buckets;
 128         timer_setup(&cb->timer, blk_stat_timer_fn, 0);
 129
 130         return cb;
 131 }
 132
 133 void blk_stat_add_callback(struct request_queue *q,
 134                            struct blk_stat_callback *cb)
 135 {
 136         unsigned int bucket;
 137         unsigned long flags;
 138         int cpu;
 139
 140         for_each_possible_cpu(cpu) {
 141                 struct blk_rq_stat *cpu_stat;
 142
 143                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
 144                 for (bucket = 0; bucket < cb->buckets; bucket++)
 145                         blk_rq_stat_init(&cpu_stat[bucket]);
 146         }
 147
 148         spin_lock_irqsave(&q->stats->lock, flags);
 149         list_add_tail_rcu(&cb->list, &q->stats->callbacks);
 150         blk_queue_flag_set(QUEUE_FLAG_STATS, q);
 151         spin_unlock_irqrestore(&q->stats->lock, flags);
 152 }
 153
 154 void blk_stat_remove_callback(struct request_queue *q,
 155                               struct blk_stat_callback *cb)
 156 {
 157         unsigned long flags;
 158
 159         spin_lock_irqsave(&q->stats->lock, flags);
 160         list_del_rcu(&cb->list);
 161         if (list_empty(&q->stats->callbacks) && !q->stats->accounting)
 162                 blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
 163         spin_unlock_irqrestore(&q->stats->lock, flags);
 164
 165         del_timer_sync(&cb->timer);
 166 }
 167
 168 static void blk_stat_free_callback_rcu(struct rcu_head *head)
 169 {
 170         struct blk_stat_callback *cb;
 171
 172         cb = container_of(head, struct blk_stat_callback, rcu);
 173         free_percpu(cb->cpu_stat);
 174         kfree(cb->stat);
 175         kfree(cb);
 176 }
 177
 178 void blk_stat_free_callback(struct blk_stat_callback *cb)
 179 {
 180         if (cb)
 181                 call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
 182 }
 183
 184 void blk_stat_disable_accounting(struct request_queue *q)
 185 {
 186         unsigned long flags;
 187
 188         spin_lock_irqsave(&q->stats->lock, flags);
 189         if (!--q->stats->accounting && list_empty(&q->stats->callbacks))
 190                 blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
 191         spin_unlock_irqrestore(&q->stats->lock, flags);
 192 }
 193 EXPORT_SYMBOL_GPL(blk_stat_disable_accounting);
 194
 195 void blk_stat_enable_accounting(struct request_queue *q)
 196 {
 197         unsigned long flags;
 198
 199         spin_lock_irqsave(&q->stats->lock, flags);
 200         if (!q->stats->accounting++ && list_empty(&q->stats->callbacks))
 201                 blk_queue_flag_set(QUEUE_FLAG_STATS, q);
 202         spin_unlock_irqrestore(&q->stats->lock, flags);
 203 }
 204 EXPORT_SYMBOL_GPL(blk_stat_enable_accounting);
 205
 206 struct blk_queue_stats *blk_alloc_queue_stats(void)
 207 {
 208         struct blk_queue_stats *stats;
 209
 210         stats = kmalloc(sizeof(*stats), GFP_KERNEL);
 211         if (!stats)
 212                 return NULL;
 213
 214         INIT_LIST_HEAD(&stats->callbacks);
 215         spin_lock_init(&stats->lock);
 216         stats->accounting = 0;
 217
 218         return stats;
 219 }
 220
 221 void blk_free_queue_stats(struct blk_queue_stats *stats)
 222 {
 223         if (!stats)
 224                 return;
 225
 226         WARN_ON(!list_empty(&stats->callbacks));
 227
 228         kfree(stats);
 229 }