block/blk-stat.c

   1 /*
   2  * Block stat tracking code
   3  *
   4  * Copyright (C) 2016 Jens Axboe
   5  */
   6 #include <linux/kernel.h>
   7 #include <linux/rculist.h>
   8 #include <linux/blk-mq.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         bool enable_accounting;
  18 };
  19
  20 static void blk_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 static void blk_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
  29 {
  30         if (!src->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 static void __blk_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)
  51 {
  52         struct request_queue *q = rq->q;
  53         struct blk_stat_callback *cb;
  54         struct blk_rq_stat *stat;
  55         int bucket;
  56         u64 now, value;
  57
  58         now = __blk_stat_time(ktime_to_ns(ktime_get()));
  59         if (now < blk_stat_time(&rq->issue_stat))
  60                 return;
  61
  62         value = now - blk_stat_time(&rq->issue_stat);
  63
  64         blk_throtl_stat_add(rq, value);
  65
  66         rcu_read_lock();
  67         list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
  68                 if (!blk_stat_is_active(cb))
  69                         continue;
  70
  71                 bucket = cb->bucket_fn(rq);
  72                 if (bucket < 0)
  73                         continue;
  74
  75                 stat = &get_cpu_ptr(cb->cpu_stat)[bucket];
  76                 __blk_stat_add(stat, value);
  77                 put_cpu_ptr(cb->cpu_stat);
  78         }
  79         rcu_read_unlock();
  80 }
  81
  82 static void blk_stat_timer_fn(unsigned long data)
  83 {
  84         struct blk_stat_callback *cb = (void *)data;
  85         unsigned int bucket;
  86         int cpu;
  87
  88         for (bucket = 0; bucket < cb->buckets; bucket++)
  89                 blk_stat_init(&cb->stat[bucket]);
  90
  91         for_each_online_cpu(cpu) {
  92                 struct blk_rq_stat *cpu_stat;
  93
  94                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
  95                 for (bucket = 0; bucket < cb->buckets; bucket++) {
  96                         blk_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
  97                         blk_stat_init(&cpu_stat[bucket]);
  98                 }
  99         }
 100
 101         cb->timer_fn(cb);
 102 }
 103
 104 struct blk_stat_callback *
 105 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 106                         int (*bucket_fn)(const struct request *),
 107                         unsigned int buckets, void *data)
 108 {
 109         struct blk_stat_callback *cb;
 110
 111         cb = kmalloc(sizeof(*cb), GFP_KERNEL);
 112         if (!cb)
 113                 return NULL;
 114
 115         cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
 116                                  GFP_KERNEL);
 117         if (!cb->stat) {
 118                 kfree(cb);
 119                 return NULL;
 120         }
 121         cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
 122                                       __alignof__(struct blk_rq_stat));
 123         if (!cb->cpu_stat) {
 124                 kfree(cb->stat);
 125                 kfree(cb);
 126                 return NULL;
 127         }
 128
 129         cb->timer_fn = timer_fn;
 130         cb->bucket_fn = bucket_fn;
 131         cb->data = data;
 132         cb->buckets = buckets;
 133         setup_timer(&cb->timer, blk_stat_timer_fn, (unsigned long)cb);
 134
 135         return cb;
 136 }
 137 EXPORT_SYMBOL_GPL(blk_stat_alloc_callback);
 138
 139 void blk_stat_add_callback(struct request_queue *q,
 140                            struct blk_stat_callback *cb)
 141 {
 142         unsigned int bucket;
 143         int cpu;
 144
 145         for_each_possible_cpu(cpu) {
 146                 struct blk_rq_stat *cpu_stat;
 147
 148                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
 149                 for (bucket = 0; bucket < cb->buckets; bucket++)
 150                         blk_stat_init(&cpu_stat[bucket]);
 151         }
 152
 153         spin_lock(&q->stats->lock);
 154         list_add_tail_rcu(&cb->list, &q->stats->callbacks);
 155         set_bit(QUEUE_FLAG_STATS, &q->queue_flags);
 156         spin_unlock(&q->stats->lock);
 157 }
 158 EXPORT_SYMBOL_GPL(blk_stat_add_callback);
 159
 160 void blk_stat_remove_callback(struct request_queue *q,
 161                               struct blk_stat_callback *cb)
 162 {
 163         spin_lock(&q->stats->lock);
 164         list_del_rcu(&cb->list);
 165         if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
 166                 clear_bit(QUEUE_FLAG_STATS, &q->queue_flags);
 167         spin_unlock(&q->stats->lock);
 168
 169         del_timer_sync(&cb->timer);
 170 }
 171 EXPORT_SYMBOL_GPL(blk_stat_remove_callback);
 172
 173 static void blk_stat_free_callback_rcu(struct rcu_head *head)
 174 {
 175         struct blk_stat_callback *cb;
 176
 177         cb = container_of(head, struct blk_stat_callback, rcu);
 178         free_percpu(cb->cpu_stat);
 179         kfree(cb->stat);
 180         kfree(cb);
 181 }
 182
 183 void blk_stat_free_callback(struct blk_stat_callback *cb)
 184 {
 185         if (cb)
 186                 call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
 187 }
 188 EXPORT_SYMBOL_GPL(blk_stat_free_callback);
 189
 190 void blk_stat_enable_accounting(struct request_queue *q)
 191 {
 192         spin_lock(&q->stats->lock);
 193         q->stats->enable_accounting = true;
 194         set_bit(QUEUE_FLAG_STATS, &q->queue_flags);
 195         spin_unlock(&q->stats->lock);
 196 }
 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 }