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 } 248