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 memset(&acc->total.cache_hits, 113 0, 114 sizeof(struct cache_stats)); 115 } 116 117 void bch_cache_accounting_destroy(struct cache_accounting *acc) 118 { 119 kobject_put(&acc->total.kobj); 120 kobject_put(&acc->five_minute.kobj); 121 kobject_put(&acc->hour.kobj); 122 kobject_put(&acc->day.kobj); 123 124 atomic_set(&acc->closing, 1); 125 if (del_timer_sync(&acc->timer)) 126 closure_return(&acc->cl); 127 } 128 129 /* EWMA scaling */ 130 131 static void scale_stat(unsigned long *stat) 132 { 133 *stat = ewma_add(*stat, 0, accounting_weight, 0); 134 } 135 136 static void scale_stats(struct cache_stats *stats, unsigned long rescale_at) 137 { 138 if (++stats->rescale == rescale_at) { 139 stats->rescale = 0; 140 scale_stat(&stats->cache_hits); 141 scale_stat(&stats->cache_misses); 142 scale_stat(&stats->cache_bypass_hits); 143 scale_stat(&stats->cache_bypass_misses); 144 scale_stat(&stats->cache_readaheads); 145 scale_stat(&stats->cache_miss_collisions); 146 scale_stat(&stats->sectors_bypassed); 147 } 148 } 149 150 static void scale_accounting(struct timer_list *t) 151 { 152 struct cache_accounting *acc = from_timer(acc, t, timer); 153 154 #define move_stat(name) do { \ 155 unsigned int t = atomic_xchg(&acc->collector.name, 0); \ 156 t <<= 16; \ 157 acc->five_minute.name += t; \ 158 acc->hour.name += t; \ 159 acc->day.name += t; \ 160 acc->total.name += t; \ 161 } while (0) 162 163 move_stat(cache_hits); 164 move_stat(cache_misses); 165 move_stat(cache_bypass_hits); 166 move_stat(cache_bypass_misses); 167 move_stat(cache_readaheads); 168 move_stat(cache_miss_collisions); 169 move_stat(sectors_bypassed); 170 171 scale_stats(&acc->total, 0); 172 scale_stats(&acc->day, DAY_RESCALE); 173 scale_stats(&acc->hour, HOUR_RESCALE); 174 scale_stats(&acc->five_minute, FIVE_MINUTE_RESCALE); 175 176 acc->timer.expires += accounting_delay; 177 178 if (!atomic_read(&acc->closing)) 179 add_timer(&acc->timer); 180 else 181 closure_return(&acc->cl); 182 } 183 184 static void mark_cache_stats(struct cache_stat_collector *stats, 185 bool hit, bool bypass) 186 { 187 if (!bypass) 188 if (hit) 189 atomic_inc(&stats->cache_hits); 190 else 191 atomic_inc(&stats->cache_misses); 192 else 193 if (hit) 194 atomic_inc(&stats->cache_bypass_hits); 195 else 196 atomic_inc(&stats->cache_bypass_misses); 197 } 198 199 void bch_mark_cache_accounting(struct cache_set *c, struct bcache_device *d, 200 bool hit, bool bypass) 201 { 202 struct cached_dev *dc = container_of(d, struct cached_dev, disk); 203 204 mark_cache_stats(&dc->accounting.collector, hit, bypass); 205 mark_cache_stats(&c->accounting.collector, hit, bypass); 206 } 207 208 void bch_mark_cache_readahead(struct cache_set *c, struct bcache_device *d) 209 { 210 struct cached_dev *dc = container_of(d, struct cached_dev, disk); 211 212 atomic_inc(&dc->accounting.collector.cache_readaheads); 213 atomic_inc(&c->accounting.collector.cache_readaheads); 214 } 215 216 void bch_mark_cache_miss_collision(struct cache_set *c, struct bcache_device *d) 217 { 218 struct cached_dev *dc = container_of(d, struct cached_dev, disk); 219 220 atomic_inc(&dc->accounting.collector.cache_miss_collisions); 221 atomic_inc(&c->accounting.collector.cache_miss_collisions); 222 } 223 224 void bch_mark_sectors_bypassed(struct cache_set *c, struct cached_dev *dc, 225 int sectors) 226 { 227 atomic_add(sectors, &dc->accounting.collector.sectors_bypassed); 228 atomic_add(sectors, &c->accounting.collector.sectors_bypassed); 229 } 230 231 void bch_cache_accounting_init(struct cache_accounting *acc, 232 struct closure *parent) 233 { 234 kobject_init(&acc->total.kobj, &bch_stats_ktype); 235 kobject_init(&acc->five_minute.kobj, &bch_stats_ktype); 236 kobject_init(&acc->hour.kobj, &bch_stats_ktype); 237 kobject_init(&acc->day.kobj, &bch_stats_ktype); 238 239 closure_init(&acc->cl, parent); 240 timer_setup(&acc->timer, scale_accounting, 0); 241 acc->timer.expires = jiffies + accounting_delay; 242 add_timer(&acc->timer); 243 } 244