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, 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;
  56         u64 value;
  57
  58         value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
  59
  60         blk_throtl_stat_add(rq, value);
  61
  62         rcu_read_lock();
  63         list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
  64                 if (!blk_stat_is_active(cb))
  65                         continue;
  66
  67                 bucket = cb->bucket_fn(rq);
  68                 if (bucket < 0)
  69                         continue;
  70
  71                 stat = &get_cpu_ptr(cb->cpu_stat)[bucket];
  72                 __blk_stat_add(stat, value);
  73                 put_cpu_ptr(cb->cpu_stat);
  74         }
  75         rcu_read_unlock();
  76 }
  77
  78 static void blk_stat_timer_fn(struct timer_list *t)
  79 {
  80         struct blk_stat_callback *cb = from_timer(cb, t, timer);
  81         unsigned int bucket;
  82         int cpu;
  83
  84         for (bucket = 0; bucket < cb->buckets; bucket++)
  85                 blk_stat_init(&cb->stat[bucket]);
  86
  87         for_each_online_cpu(cpu) {
  88                 struct blk_rq_stat *cpu_stat;
  89
  90                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
  91                 for (bucket = 0; bucket < cb->buckets; bucket++) {
  92                         blk_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
  93                         blk_stat_init(&cpu_stat[bucket]);
  94                 }
  95         }
  96
  97         cb->timer_fn(cb);
  98 }
  99
 100 struct blk_stat_callback *
 101 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 102                         int (*bucket_fn)(const struct request *),
 103                         unsigned int buckets, void *data)
 104 {
 105         struct blk_stat_callback *cb;
 106
 107         cb = kmalloc(sizeof(*cb), GFP_KERNEL);
 108         if (!cb)
 109                 return NULL;
 110
 111         cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
 112                                  GFP_KERNEL);
 113         if (!cb->stat) {
 114                 kfree(cb);
 115                 return NULL;
 116         }
 117         cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
 118                                       __alignof__(struct blk_rq_stat));
 119         if (!cb->cpu_stat) {
 120                 kfree(cb->stat);
 121                 kfree(cb);
 122                 return NULL;
 123         }
 124
 125         cb->timer_fn = timer_fn;
 126         cb->bucket_fn = bucket_fn;
 127         cb->data = data;
 128         cb->buckets = buckets;
 129         timer_setup(&cb->timer, blk_stat_timer_fn, 0);
 130
 131         return cb;
 132 }
 133 EXPORT_SYMBOL_GPL(blk_stat_alloc_callback);
 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_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 EXPORT_SYMBOL_GPL(blk_stat_add_callback);
 155
 156 void blk_stat_remove_callback(struct request_queue *q,
 157                               struct blk_stat_callback *cb)
 158 {
 159         spin_lock(&q->stats->lock);
 160         list_del_rcu(&cb->list);
 161         if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
 162                 blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
 163         spin_unlock(&q->stats->lock);
 164
 165         del_timer_sync(&cb->timer);
 166 }
 167 EXPORT_SYMBOL_GPL(blk_stat_remove_callback);
 168
 169 static void blk_stat_free_callback_rcu(struct rcu_head *head)
 170 {
 171         struct blk_stat_callback *cb;
 172
 173         cb = container_of(head, struct blk_stat_callback, rcu);
 174         free_percpu(cb->cpu_stat);
 175         kfree(cb->stat);
 176         kfree(cb);
 177 }
 178
 179 void blk_stat_free_callback(struct blk_stat_callback *cb)
 180 {
 181         if (cb)
 182                 call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
 183 }
 184 EXPORT_SYMBOL_GPL(blk_stat_free_callback);
 185
 186 void blk_stat_enable_accounting(struct request_queue *q)
 187 {
 188         spin_lock(&q->stats->lock);
 189         q->stats->enable_accounting = true;
 190         blk_queue_flag_set(QUEUE_FLAG_STATS, q);
 191         spin_unlock(&q->stats->lock);
 192 }
 193
 194 struct blk_queue_stats *blk_alloc_queue_stats(void)
 195 {
 196         struct blk_queue_stats *stats;
 197
 198         stats = kmalloc(sizeof(*stats), GFP_KERNEL);
 199         if (!stats)
 200                 return NULL;
 201
 202         INIT_LIST_HEAD(&stats->callbacks);
 203         spin_lock_init(&stats->lock);
 204         stats->enable_accounting = false;
 205
 206         return stats;
 207 }
 208
 209 void blk_free_queue_stats(struct blk_queue_stats *stats)
 210 {
 211         if (!stats)
 212                 return;
 213
 214         WARN_ON(!list_empty(&stats->callbacks));
 215
 216         kfree(stats);
 217 }