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
  13 #define BLK_RQ_STAT_BATCH       64
  14
  15 struct blk_queue_stats {
  16         struct list_head callbacks;
  17         spinlock_t lock;
  18 };
  19
  20 unsigned int blk_stat_rq_ddir(const struct request *rq)
  21 {
  22         return rq_data_dir(rq);
  23 }
  24 EXPORT_SYMBOL_GPL(blk_stat_rq_ddir);
  25
  26 static void blk_stat_init(struct blk_rq_stat *stat)
  27 {
  28         stat->min = -1ULL;
  29         stat->max = stat->nr_samples = stat->mean = 0;
  30         stat->batch = stat->nr_batch = 0;
  31 }
  32
  33 static void blk_stat_flush_batch(struct blk_rq_stat *stat)
  34 {
  35         const s32 nr_batch = READ_ONCE(stat->nr_batch);
  36         const s32 nr_samples = READ_ONCE(stat->nr_samples);
  37
  38         if (!nr_batch)
  39                 return;
  40         if (!nr_samples)
  41                 stat->mean = div64_s64(stat->batch, nr_batch);
  42         else {
  43                 stat->mean = div64_s64((stat->mean * nr_samples) +
  44                                         stat->batch,
  45                                         nr_batch + nr_samples);
  46         }
  47
  48         stat->nr_samples += nr_batch;
  49         stat->nr_batch = stat->batch = 0;
  50 }
  51
  52 static void blk_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
  53 {
  54         blk_stat_flush_batch(src);
  55
  56         if (!src->nr_samples)
  57                 return;
  58
  59         dst->min = min(dst->min, src->min);
  60         dst->max = max(dst->max, src->max);
  61
  62         if (!dst->nr_samples)
  63                 dst->mean = src->mean;
  64         else {
  65                 dst->mean = div64_s64((src->mean * src->nr_samples) +
  66                                         (dst->mean * dst->nr_samples),
  67                                         dst->nr_samples + src->nr_samples);
  68         }
  69         dst->nr_samples += src->nr_samples;
  70 }
  71
  72 static void __blk_stat_add(struct blk_rq_stat *stat, u64 value)
  73 {
  74         stat->min = min(stat->min, value);
  75         stat->max = max(stat->max, value);
  76
  77         if (stat->batch + value < stat->batch ||
  78             stat->nr_batch + 1 == BLK_RQ_STAT_BATCH)
  79                 blk_stat_flush_batch(stat);
  80
  81         stat->batch += value;
  82         stat->nr_batch++;
  83 }
  84
  85 void blk_stat_add(struct request *rq)
  86 {
  87         struct request_queue *q = rq->q;
  88         struct blk_stat_callback *cb;
  89         struct blk_rq_stat *stat;
  90         int bucket;
  91         s64 now, value;
  92
  93         now = __blk_stat_time(ktime_to_ns(ktime_get()));
  94         if (now < blk_stat_time(&rq->issue_stat))
  95                 return;
  96
  97         value = now - blk_stat_time(&rq->issue_stat);
  98
  99         rcu_read_lock();
 100         list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
 101                 if (blk_stat_is_active(cb)) {
 102                         bucket = cb->bucket_fn(rq);
 103                         stat = &this_cpu_ptr(cb->cpu_stat)[bucket];
 104                         __blk_stat_add(stat, value);
 105                 }
 106         }
 107         rcu_read_unlock();
 108 }
 109
 110 static void blk_stat_timer_fn(unsigned long data)
 111 {
 112         struct blk_stat_callback *cb = (void *)data;
 113         unsigned int bucket;
 114         int cpu;
 115
 116         for (bucket = 0; bucket < cb->buckets; bucket++)
 117                 blk_stat_init(&cb->stat[bucket]);
 118
 119         for_each_online_cpu(cpu) {
 120                 struct blk_rq_stat *cpu_stat;
 121
 122                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
 123                 for (bucket = 0; bucket < cb->buckets; bucket++) {
 124                         blk_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
 125                         blk_stat_init(&cpu_stat[bucket]);
 126                 }
 127         }
 128
 129         cb->timer_fn(cb);
 130 }
 131
 132 struct blk_stat_callback *
 133 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 134                         unsigned int (*bucket_fn)(const struct request *),
 135                         unsigned int buckets, void *data)
 136 {
 137         struct blk_stat_callback *cb;
 138
 139         cb = kmalloc(sizeof(*cb), GFP_KERNEL);
 140         if (!cb)
 141                 return NULL;
 142
 143         cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
 144                                  GFP_KERNEL);
 145         if (!cb->stat) {
 146                 kfree(cb);
 147                 return NULL;
 148         }
 149         cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
 150                                       __alignof__(struct blk_rq_stat));
 151         if (!cb->cpu_stat) {
 152                 kfree(cb->stat);
 153                 kfree(cb);
 154                 return NULL;
 155         }
 156
 157         cb->timer_fn = timer_fn;
 158         cb->bucket_fn = bucket_fn;
 159         cb->data = data;
 160         cb->buckets = buckets;
 161         setup_timer(&cb->timer, blk_stat_timer_fn, (unsigned long)cb);
 162
 163         return cb;
 164 }
 165 EXPORT_SYMBOL_GPL(blk_stat_alloc_callback);
 166
 167 void blk_stat_add_callback(struct request_queue *q,
 168                            struct blk_stat_callback *cb)
 169 {
 170         unsigned int bucket;
 171         int cpu;
 172
 173         for_each_possible_cpu(cpu) {
 174                 struct blk_rq_stat *cpu_stat;
 175
 176                 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
 177                 for (bucket = 0; bucket < cb->buckets; bucket++)
 178                         blk_stat_init(&cpu_stat[bucket]);
 179         }
 180
 181         spin_lock(&q->stats->lock);
 182         list_add_tail_rcu(&cb->list, &q->stats->callbacks);
 183         set_bit(QUEUE_FLAG_STATS, &q->queue_flags);
 184         spin_unlock(&q->stats->lock);
 185 }
 186 EXPORT_SYMBOL_GPL(blk_stat_add_callback);
 187
 188 void blk_stat_remove_callback(struct request_queue *q,
 189                               struct blk_stat_callback *cb)
 190 {
 191         spin_lock(&q->stats->lock);
 192         list_del_rcu(&cb->list);
 193         if (list_empty(&q->stats->callbacks))
 194                 clear_bit(QUEUE_FLAG_STATS, &q->queue_flags);
 195         spin_unlock(&q->stats->lock);
 196
 197         del_timer_sync(&cb->timer);
 198 }
 199 EXPORT_SYMBOL_GPL(blk_stat_remove_callback);
 200
 201 static void blk_stat_free_callback_rcu(struct rcu_head *head)
 202 {
 203         struct blk_stat_callback *cb;
 204
 205         cb = container_of(head, struct blk_stat_callback, rcu);
 206         free_percpu(cb->cpu_stat);
 207         kfree(cb->stat);
 208         kfree(cb);
 209 }
 210
 211 void blk_stat_free_callback(struct blk_stat_callback *cb)
 212 {
 213         if (cb)
 214                 call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
 215 }
 216 EXPORT_SYMBOL_GPL(blk_stat_free_callback);
 217
 218 struct blk_queue_stats *blk_alloc_queue_stats(void)
 219 {
 220         struct blk_queue_stats *stats;
 221
 222         stats = kmalloc(sizeof(*stats), GFP_KERNEL);
 223         if (!stats)
 224                 return NULL;
 225
 226         INIT_LIST_HEAD(&stats->callbacks);
 227         spin_lock_init(&stats->lock);
 228
 229         return stats;
 230 }
 231
 232 void blk_free_queue_stats(struct blk_queue_stats *stats)
 233 {
 234         if (!stats)
 235                 return;
 236
 237         WARN_ON(!list_empty(&stats->callbacks));
 238
 239         kfree(stats);
 240 }