root/drivers/md/bcache/stats.c

DEFINITIONS

1. SHOW
2. STORE
3. bch_stats_release
4. bch_cache_accounting_add_kobjs
5. bch_cache_accounting_clear
6. bch_cache_accounting_destroy
7. scale_stat
8. scale_stats
9. scale_accounting
10. mark_cache_stats
11. bch_mark_cache_accounting
12. bch_mark_cache_readahead
13. bch_mark_cache_miss_collision
14. bch_mark_sectors_bypassed
15. bch_cache_accounting_init

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * bcache stats code
   4  *
   5  * Copyright 2012 Google, Inc.
   6  */
   7 
   8 #include "bcache.h"
   9 #include "stats.h"
  10 #include "btree.h"
  11 #include "sysfs.h"
  12 
  13 /*
  14  * We keep absolute totals of various statistics, and addionally a set of three
  15  * rolling averages.
  16  *
  17  * Every so often, a timer goes off and rescales the rolling averages.
  18  * accounting_rescale[] is how many times the timer has to go off before we
  19  * rescale each set of numbers; that gets us half lives of 5 minutes, one hour,
  20  * and one day.
  21  *
  22  * accounting_delay is how often the timer goes off - 22 times in 5 minutes,
  23  * and accounting_weight is what we use to rescale:
  24  *
  25  * pow(31 / 32, 22) ~= 1/2
  26  *
  27  * So that we don't have to increment each set of numbers every time we (say)
  28  * get a cache hit, we increment a single atomic_t in acc->collector, and when
  29  * the rescale function runs it resets the atomic counter to 0 and adds its
  30  * old value to each of the exported numbers.
  31  *
  32  * To reduce rounding error, the numbers in struct cache_stats are all
  33  * stored left shifted by 16, and scaled back in the sysfs show() function.
  34  */
  35 
  36 static const unsigned int DAY_RESCALE           = 288;
  37 static const unsigned int HOUR_RESCALE          = 12;
  38 static const unsigned int FIVE_MINUTE_RESCALE   = 1;
  39 static const unsigned int accounting_delay      = (HZ * 300) / 22;
  40 static const unsigned int accounting_weight     = 32;
  41 
  42 /* sysfs reading/writing */
  43 
  44 read_attribute(cache_hits);
  45 read_attribute(cache_misses);
  46 read_attribute(cache_bypass_hits);
  47 read_attribute(cache_bypass_misses);
  48 read_attribute(cache_hit_ratio);
  49 read_attribute(cache_readaheads);
  50 read_attribute(cache_miss_collisions);
  51 read_attribute(bypassed);
  52 
  53 SHOW(bch_stats)
  54 {
  55         struct cache_stats *s =
  56                 container_of(kobj, struct cache_stats, kobj);
  57 #define var(stat)               (s->stat >> 16)
  58         var_print(cache_hits);
  59         var_print(cache_misses);
  60         var_print(cache_bypass_hits);
  61         var_print(cache_bypass_misses);
  62 
  63         sysfs_print(cache_hit_ratio,
  64                     DIV_SAFE(var(cache_hits) * 100,
  65                              var(cache_hits) + var(cache_misses)));
  66 
  67         var_print(cache_readaheads);
  68         var_print(cache_miss_collisions);
  69         sysfs_hprint(bypassed,  var(sectors_bypassed) << 9);
  70 #undef var
  71         return 0;
  72 }
  73 
  74 STORE(bch_stats)
  75 {
  76         return size;
  77 }
  78 
  79 static void bch_stats_release(struct kobject *k)
  80 {
  81 }
  82 
  83 static struct attribute *bch_stats_files[] = {
  84         &sysfs_cache_hits,
  85         &sysfs_cache_misses,
  86         &sysfs_cache_bypass_hits,
  87         &sysfs_cache_bypass_misses,
  88         &sysfs_cache_hit_ratio,
  89         &sysfs_cache_readaheads,
  90         &sysfs_cache_miss_collisions,
  91         &sysfs_bypassed,
  92         NULL
  93 };
  94 static KTYPE(bch_stats);
  95 
  96 int bch_cache_accounting_add_kobjs(struct cache_accounting *acc,
  97                                    struct kobject *parent)
  98 {
  99         int ret = kobject_add(&acc->total.kobj, parent,
 100                               "stats_total");
 101         ret = ret ?: kobject_add(&acc->five_minute.kobj, parent,
 102                                  "stats_five_minute");
 103         ret = ret ?: kobject_add(&acc->hour.kobj, parent,
 104                                  "stats_hour");
 105         ret = ret ?: kobject_add(&acc->day.kobj, parent,
 106                                  "stats_day");
 107         return ret;
 108 }
 109 
 110 void bch_cache_accounting_clear(struct cache_accounting *acc)
 111 {
 112         acc->total.cache_hits = 0;
 113         acc->total.cache_misses = 0;
 114         acc->total.cache_bypass_hits = 0;
 115         acc->total.cache_bypass_misses = 0;
 116         acc->total.cache_readaheads = 0;
 117         acc->total.cache_miss_collisions = 0;
 118         acc->total.sectors_bypassed = 0;
 119 }
 120 
 121 void bch_cache_accounting_destroy(struct cache_accounting *acc)
 122 {
 123         kobject_put(&acc->total.kobj);
 124         kobject_put(&acc->five_minute.kobj);
 125         kobject_put(&acc->hour.kobj);
 126         kobject_put(&acc->day.kobj);
 127 
 128         atomic_set(&acc->closing, 1);
 129         if (del_timer_sync(&acc->timer))
 130                 closure_return(&acc->cl);
 131 }
 132 
 133 /* EWMA scaling */
 134 
 135 static void scale_stat(unsigned long *stat)
 136 {
 137         *stat =  ewma_add(*stat, 0, accounting_weight, 0);
 138 }
 139 
 140 static void scale_stats(struct cache_stats *stats, unsigned long rescale_at)
 141 {
 142         if (++stats->rescale == rescale_at) {
 143                 stats->rescale = 0;
 144                 scale_stat(&stats->cache_hits);
 145                 scale_stat(&stats->cache_misses);
 146                 scale_stat(&stats->cache_bypass_hits);
 147                 scale_stat(&stats->cache_bypass_misses);
 148                 scale_stat(&stats->cache_readaheads);
 149                 scale_stat(&stats->cache_miss_collisions);
 150                 scale_stat(&stats->sectors_bypassed);
 151         }
 152 }
 153 
 154 static void scale_accounting(struct timer_list *t)
 155 {
 156         struct cache_accounting *acc = from_timer(acc, t, timer);
 157 
 158 #define move_stat(name) do {                                            \
 159         unsigned int t = atomic_xchg(&acc->collector.name, 0);          \
 160         t <<= 16;                                                       \
 161         acc->five_minute.name += t;                                     \
 162         acc->hour.name += t;                                            \
 163         acc->day.name += t;                                             \
 164         acc->total.name += t;                                           \
 165 } while (0)
 166 
 167         move_stat(cache_hits);
 168         move_stat(cache_misses);
 169         move_stat(cache_bypass_hits);
 170         move_stat(cache_bypass_misses);
 171         move_stat(cache_readaheads);
 172         move_stat(cache_miss_collisions);
 173         move_stat(sectors_bypassed);
 174 
 175         scale_stats(&acc->total, 0);
 176         scale_stats(&acc->day, DAY_RESCALE);
 177         scale_stats(&acc->hour, HOUR_RESCALE);
 178         scale_stats(&acc->five_minute, FIVE_MINUTE_RESCALE);
 179 
 180         acc->timer.expires += accounting_delay;
 181 
 182         if (!atomic_read(&acc->closing))
 183                 add_timer(&acc->timer);
 184         else
 185                 closure_return(&acc->cl);
 186 }
 187 
 188 static void mark_cache_stats(struct cache_stat_collector *stats,
 189                              bool hit, bool bypass)
 190 {
 191         if (!bypass)
 192                 if (hit)
 193                         atomic_inc(&stats->cache_hits);
 194                 else
 195                         atomic_inc(&stats->cache_misses);
 196         else
 197                 if (hit)
 198                         atomic_inc(&stats->cache_bypass_hits);
 199                 else
 200                         atomic_inc(&stats->cache_bypass_misses);
 201 }
 202 
 203 void bch_mark_cache_accounting(struct cache_set *c, struct bcache_device *d,
 204                                bool hit, bool bypass)
 205 {
 206         struct cached_dev *dc = container_of(d, struct cached_dev, disk);
 207 
 208         mark_cache_stats(&dc->accounting.collector, hit, bypass);
 209         mark_cache_stats(&c->accounting.collector, hit, bypass);
 210 }
 211 
 212 void bch_mark_cache_readahead(struct cache_set *c, struct bcache_device *d)
 213 {
 214         struct cached_dev *dc = container_of(d, struct cached_dev, disk);
 215 
 216         atomic_inc(&dc->accounting.collector.cache_readaheads);
 217         atomic_inc(&c->accounting.collector.cache_readaheads);
 218 }
 219 
 220 void bch_mark_cache_miss_collision(struct cache_set *c, struct bcache_device *d)
 221 {
 222         struct cached_dev *dc = container_of(d, struct cached_dev, disk);
 223 
 224         atomic_inc(&dc->accounting.collector.cache_miss_collisions);
 225         atomic_inc(&c->accounting.collector.cache_miss_collisions);
 226 }
 227 
 228 void bch_mark_sectors_bypassed(struct cache_set *c, struct cached_dev *dc,
 229                                int sectors)
 230 {
 231         atomic_add(sectors, &dc->accounting.collector.sectors_bypassed);
 232         atomic_add(sectors, &c->accounting.collector.sectors_bypassed);
 233 }
 234 
 235 void bch_cache_accounting_init(struct cache_accounting *acc,
 236                                struct closure *parent)
 237 {
 238         kobject_init(&acc->total.kobj,          &bch_stats_ktype);
 239         kobject_init(&acc->five_minute.kobj,    &bch_stats_ktype);
 240         kobject_init(&acc->hour.kobj,           &bch_stats_ktype);
 241         kobject_init(&acc->day.kobj,            &bch_stats_ktype);
 242 
 243         closure_init(&acc->cl, parent);
 244         timer_setup(&acc->timer, scale_accounting, 0);
 245         acc->timer.expires      = jiffies + accounting_delay;
 246         add_timer(&acc->timer);
 247 }