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/*
* bcache stats code
*
* Copyright 2012 Google, Inc.
*/
#include "bcache.h"
#include "stats.h"
#include "btree.h"
#include "sysfs.h"
/*
* We keep absolute totals of various statistics, and addionally a set of three
* rolling averages.
*
* Every so often, a timer goes off and rescales the rolling averages.
* accounting_rescale[] is how many times the timer has to go off before we
* rescale each set of numbers; that gets us half lives of 5 minutes, one hour,
* and one day.
*
* accounting_delay is how often the timer goes off - 22 times in 5 minutes,
* and accounting_weight is what we use to rescale:
*
* pow(31 / 32, 22) ~= 1/2
*
* So that we don't have to increment each set of numbers every time we (say)
* get a cache hit, we increment a single atomic_t in acc->collector, and when
* the rescale function runs it resets the atomic counter to 0 and adds its
* old value to each of the exported numbers.
*
* To reduce rounding error, the numbers in struct cache_stats are all
* stored left shifted by 16, and scaled back in the sysfs show() function.
*/
static const unsigned DAY_RESCALE = 288;
static const unsigned HOUR_RESCALE = 12;
static const unsigned FIVE_MINUTE_RESCALE = 1;
static const unsigned accounting_delay = (HZ * 300) / 22;
static const unsigned accounting_weight = 32;
/* sysfs reading/writing */
read_attribute(cache_hits);
read_attribute(cache_misses);
read_attribute(cache_bypass_hits);
read_attribute(cache_bypass_misses);
read_attribute(cache_hit_ratio);
read_attribute(cache_readaheads);
read_attribute(cache_miss_collisions);
read_attribute(bypassed);
SHOW(bch_stats)
{
struct cache_stats *s =
container_of(kobj, struct cache_stats, kobj);
#define var(stat) (s->stat >> 16)
var_print(cache_hits);
var_print(cache_misses);
var_print(cache_bypass_hits);
var_print(cache_bypass_misses);
sysfs_print(cache_hit_ratio,
DIV_SAFE(var(cache_hits) * 100,
var(cache_hits) + var(cache_misses)));
var_print(cache_readaheads);
var_print(cache_miss_collisions);
sysfs_hprint(bypassed, var(sectors_bypassed) << 9);
#undef var
return 0;
}
STORE(bch_stats)
{
return size;
}
static void bch_stats_release(struct kobject *k)
{
}
static struct attribute *bch_stats_files[] = {
&sysfs_cache_hits,
&sysfs_cache_misses,
&sysfs_cache_bypass_hits,
&sysfs_cache_bypass_misses,
&sysfs_cache_hit_ratio,
&sysfs_cache_readaheads,
&sysfs_cache_miss_collisions,
&sysfs_bypassed,
NULL
};
static KTYPE(bch_stats);
int bch_cache_accounting_add_kobjs(struct cache_accounting *acc,
struct kobject *parent)
{
int ret = kobject_add(&acc->total.kobj, parent,
"stats_total");
ret = ret ?: kobject_add(&acc->five_minute.kobj, parent,
"stats_five_minute");
ret = ret ?: kobject_add(&acc->hour.kobj, parent,
"stats_hour");
ret = ret ?: kobject_add(&acc->day.kobj, parent,
"stats_day");
return ret;
}
void bch_cache_accounting_clear(struct cache_accounting *acc)
{
memset(&acc->total.cache_hits,
0,
sizeof(unsigned long) * 7);
}
void bch_cache_accounting_destroy(struct cache_accounting *acc)
{
kobject_put(&acc->total.kobj);
kobject_put(&acc->five_minute.kobj);
kobject_put(&acc->hour.kobj);
kobject_put(&acc->day.kobj);
atomic_set(&acc->closing, 1);
if (del_timer_sync(&acc->timer))
closure_return(&acc->cl);
}
/* EWMA scaling */
static void scale_stat(unsigned long *stat)
{
*stat = ewma_add(*stat, 0, accounting_weight, 0);
}
static void scale_stats(struct cache_stats *stats, unsigned long rescale_at)
{
if (++stats->rescale == rescale_at) {
stats->rescale = 0;
scale_stat(&stats->cache_hits);
scale_stat(&stats->cache_misses);
scale_stat(&stats->cache_bypass_hits);
scale_stat(&stats->cache_bypass_misses);
scale_stat(&stats->cache_readaheads);
scale_stat(&stats->cache_miss_collisions);
scale_stat(&stats->sectors_bypassed);
}
}
static void scale_accounting(unsigned long data)
{
struct cache_accounting *acc = (struct cache_accounting *) data;
#define move_stat(name) do { \
unsigned t = atomic_xchg(&acc->collector.name, 0); \
t <<= 16; \
acc->five_minute.name += t; \
acc->hour.name += t; \
acc->day.name += t; \
acc->total.name += t; \
} while (0)
move_stat(cache_hits);
move_stat(cache_misses);
move_stat(cache_bypass_hits);
move_stat(cache_bypass_misses);
move_stat(cache_readaheads);
move_stat(cache_miss_collisions);
move_stat(sectors_bypassed);
scale_stats(&acc->total, 0);
scale_stats(&acc->day, DAY_RESCALE);
scale_stats(&acc->hour, HOUR_RESCALE);
scale_stats(&acc->five_minute, FIVE_MINUTE_RESCALE);
acc->timer.expires += accounting_delay;
if (!atomic_read(&acc->closing))
add_timer(&acc->timer);
else
closure_return(&acc->cl);
}
static void mark_cache_stats(struct cache_stat_collector *stats,
bool hit, bool bypass)
{
if (!bypass)
if (hit)
atomic_inc(&stats->cache_hits);
else
atomic_inc(&stats->cache_misses);
else
if (hit)
atomic_inc(&stats->cache_bypass_hits);
else
atomic_inc(&stats->cache_bypass_misses);
}
void bch_mark_cache_accounting(struct cache_set *c, struct bcache_device *d,
bool hit, bool bypass)
{
struct cached_dev *dc = container_of(d, struct cached_dev, disk);
mark_cache_stats(&dc->accounting.collector, hit, bypass);
mark_cache_stats(&c->accounting.collector, hit, bypass);
}
void bch_mark_cache_readahead(struct cache_set *c, struct bcache_device *d)
{
struct cached_dev *dc = container_of(d, struct cached_dev, disk);
atomic_inc(&dc->accounting.collector.cache_readaheads);
atomic_inc(&c->accounting.collector.cache_readaheads);
}
void bch_mark_cache_miss_collision(struct cache_set *c, struct bcache_device *d)
{
struct cached_dev *dc = container_of(d, struct cached_dev, disk);
atomic_inc(&dc->accounting.collector.cache_miss_collisions);
atomic_inc(&c->accounting.collector.cache_miss_collisions);
}
void bch_mark_sectors_bypassed(struct cache_set *c, struct cached_dev *dc,
int sectors)
{
atomic_add(sectors, &dc->accounting.collector.sectors_bypassed);
atomic_add(sectors, &c->accounting.collector.sectors_bypassed);
}
void bch_cache_accounting_init(struct cache_accounting *acc,
struct closure *parent)
{
kobject_init(&acc->total.kobj, &bch_stats_ktype);
kobject_init(&acc->five_minute.kobj, &bch_stats_ktype);
kobject_init(&acc->hour.kobj, &bch_stats_ktype);
kobject_init(&acc->day.kobj, &bch_stats_ktype);
closure_init(&acc->cl, parent);
init_timer(&acc->timer);
acc->timer.expires = jiffies + accounting_delay;
acc->timer.data = (unsigned long) acc;
acc->timer.function = scale_accounting;
add_timer(&acc->timer);
}
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