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
|
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/gfp.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/ktime.h>
#include <linux/percpu.h>
#include <linux/seq_buf.h>
#include <linux/spinlock.h>
#include <linux/time_stats.h>
#include <linux/timekeeping.h>
static inline unsigned int eytzinger1_child(unsigned int i, unsigned int child)
{
return (i << 1) + child;
}
static inline unsigned int eytzinger1_right_child(unsigned int i)
{
return eytzinger1_child(i, 1);
}
static inline unsigned int eytzinger1_next(unsigned int i, unsigned int size)
{
if (eytzinger1_right_child(i) <= size) {
i = eytzinger1_right_child(i);
i <<= __fls(size + 1) - __fls(i);
i >>= i > size;
} else {
i >>= ffz(i) + 1;
}
return i;
}
static inline unsigned int eytzinger0_child(unsigned int i, unsigned int child)
{
return (i << 1) + 1 + child;
}
static inline unsigned int eytzinger0_first(unsigned int size)
{
return rounddown_pow_of_two(size) - 1;
}
static inline unsigned int eytzinger0_next(unsigned int i, unsigned int size)
{
return eytzinger1_next(i + 1, size) - 1;
}
#define eytzinger0_for_each(_i, _size) \
for ((_i) = eytzinger0_first((_size)); \
(_i) != -1; \
(_i) = eytzinger0_next((_i), (_size)))
#define ewma_add(ewma, val, weight) \
({ \
typeof(ewma) _ewma = (ewma); \
typeof(weight) _weight = (weight); \
\
(((_ewma << _weight) - _ewma) + (val)) >> _weight; \
})
static void quantiles_update(struct quantiles *q, u64 v)
{
unsigned int i = 0;
while (i < ARRAY_SIZE(q->entries)) {
struct quantile_entry *e = q->entries + i;
if (unlikely(!e->step)) {
e->m = v;
e->step = max_t(unsigned int, v / 2, 1024);
} else if (e->m > v) {
e->m = e->m >= e->step
? e->m - e->step
: 0;
} else if (e->m < v) {
e->m = e->m + e->step > e->m
? e->m + e->step
: U32_MAX;
}
if ((e->m > v ? e->m - v : v - e->m) < e->step)
e->step = max_t(unsigned int, e->step / 2, 1);
if (v >= e->m)
break;
i = eytzinger0_child(i, v > e->m);
}
}
static void time_stats_update_one(struct time_stats *stats,
u64 start, u64 end)
{
u64 duration, freq;
duration = time_after64(end, start)
? end - start : 0;
freq = time_after64(end, stats->last_event)
? end - stats->last_event : 0;
stats->count++;
stats->average_duration = stats->average_duration
? ewma_add(stats->average_duration, duration, 6)
: duration;
stats->average_frequency = stats->average_frequency
? ewma_add(stats->average_frequency, freq, 6)
: freq;
stats->max_duration = max(stats->max_duration, duration);
stats->last_event = end;
quantiles_update(&stats->quantiles, duration);
}
void time_stats_update(struct time_stats *stats, u64 start)
{
u64 end = ktime_get_ns();
unsigned long flags;
if (!stats->buffer) {
spin_lock_irqsave(&stats->lock, flags);
time_stats_update_one(stats, start, end);
if (stats->average_frequency < 32 &&
stats->count > 1024)
stats->buffer =
alloc_percpu_gfp(struct time_stat_buffer,
GFP_ATOMIC);
spin_unlock_irqrestore(&stats->lock, flags);
} else {
struct time_stat_buffer_entry *i;
struct time_stat_buffer *b;
preempt_disable();
b = this_cpu_ptr(stats->buffer);
BUG_ON(b->nr >= ARRAY_SIZE(b->entries));
b->entries[b->nr++] = (struct time_stat_buffer_entry) {
.start = start,
.end = end
};
if (b->nr == ARRAY_SIZE(b->entries)) {
spin_lock_irqsave(&stats->lock, flags);
for (i = b->entries;
i < b->entries + ARRAY_SIZE(b->entries);
i++)
time_stats_update_one(stats, i->start, i->end);
spin_unlock_irqrestore(&stats->lock, flags);
b->nr = 0;
}
preempt_enable();
}
}
EXPORT_SYMBOL(time_stats_update);
static const struct time_unit {
const char *name;
u32 nsecs;
} time_units[] = {
{ "ns", 1 },
{ "us", NSEC_PER_USEC },
{ "ms", NSEC_PER_MSEC },
{ "sec", NSEC_PER_SEC },
};
static const struct time_unit *pick_time_units(u64 ns)
{
const struct time_unit *u;
for (u = time_units;
u + 1 < time_units + ARRAY_SIZE(time_units) &&
ns >= u[1].nsecs << 1;
u++)
;
return u;
}
static void pr_time_units(struct seq_buf *out, u64 ns)
{
const struct time_unit *u = pick_time_units(ns);
seq_buf_printf(out, "%llu %s", div_u64(ns, u->nsecs), u->name);
}
void time_stats_to_text(struct seq_buf *out, struct time_stats *stats)
{
const struct time_unit *u;
u64 freq = READ_ONCE(stats->average_frequency);
u64 q, last_q = 0;
int i;
seq_buf_printf(out, "count: %llu\n", stats->count);
seq_buf_printf(out, "rate: %llu/sec\n",
freq ? div64_u64(NSEC_PER_SEC, freq) : 0);
seq_buf_printf(out, "frequency: ");
pr_time_units(out, freq);
seq_buf_putc(out, '\n');
seq_buf_printf(out, "avg duration: ");
pr_time_units(out, stats->average_duration);
seq_buf_putc(out, '\n');
seq_buf_printf(out, "max duration: ");
pr_time_units(out, stats->max_duration);
seq_buf_putc(out, '\n');
i = eytzinger0_first(NR_QUANTILES);
u = pick_time_units(stats->quantiles.entries[i].m);
seq_buf_printf(out, "quantiles (%s): ", u->name);
eytzinger0_for_each(i, NR_QUANTILES) {
q = max(stats->quantiles.entries[i].m, last_q);
seq_buf_printf(out, "%llu ", div_u64(q, u->nsecs));
last_q = q;
}
seq_buf_putc(out, '\n');
}
EXPORT_SYMBOL_GPL(time_stats_to_text);
void time_stats_exit(struct time_stats *stats)
{
free_percpu(stats->buffer);
stats->buffer = NULL;
}
EXPORT_SYMBOL_GPL(time_stats_exit);
|
