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