1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
|
// SPDX-License-Identifier: GPL-2.0
/*
* 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);
}
|
