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
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* x86 APERF/MPERF KHz calculation for
* /sys/.../cpufreq/scaling_cur_freq
*
* Copyright (C) 2017 Intel Corp.
* Author: Len Brown <len.brown@intel.com>
*/
#include <linux/delay.h>
#include <linux/ktime.h>
#include <linux/math64.h>
#include <linux/percpu.h>
#include <linux/cpufreq.h>
#include <linux/smp.h>
#include <linux/sched/isolation.h>
#include <linux/rcupdate.h>
#include "cpu.h"
struct aperfmperf_sample {
unsigned int khz;
atomic_t scfpending;
ktime_t time;
u64 aperf;
u64 mperf;
};
static DEFINE_PER_CPU(struct aperfmperf_sample, samples);
#define APERFMPERF_CACHE_THRESHOLD_MS 10
#define APERFMPERF_REFRESH_DELAY_MS 10
#define APERFMPERF_STALE_THRESHOLD_MS 1000
/*
* aperfmperf_snapshot_khz()
* On the current CPU, snapshot APERF, MPERF, and jiffies
* unless we already did it within 10ms
* calculate kHz, save snapshot
*/
static void aperfmperf_snapshot_khz(void *dummy)
{
u64 aperf, aperf_delta;
u64 mperf, mperf_delta;
struct aperfmperf_sample *s = this_cpu_ptr(&samples);
unsigned long flags;
local_irq_save(flags);
rdmsrl(MSR_IA32_APERF, aperf);
rdmsrl(MSR_IA32_MPERF, mperf);
local_irq_restore(flags);
aperf_delta = aperf - s->aperf;
mperf_delta = mperf - s->mperf;
/*
* There is no architectural guarantee that MPERF
* increments faster than we can read it.
*/
if (mperf_delta == 0)
return;
s->time = ktime_get();
s->aperf = aperf;
s->mperf = mperf;
s->khz = div64_u64((cpu_khz * aperf_delta), mperf_delta);
atomic_set_release(&s->scfpending, 0);
}
static bool aperfmperf_snapshot_cpu(int cpu, ktime_t now, bool wait)
{
s64 time_delta = ktime_ms_delta(now, per_cpu(samples.time, cpu));
struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu);
/* Don't bother re-computing within the cache threshold time. */
if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS)
return true;
if (!atomic_xchg(&s->scfpending, 1) || wait)
smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, wait);
/* Return false if the previous iteration was too long ago. */
return time_delta <= APERFMPERF_STALE_THRESHOLD_MS;
}
unsigned int aperfmperf_get_khz(int cpu)
{
if (!cpu_khz)
return 0;
if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
return 0;
if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
return 0;
if (rcu_is_idle_cpu(cpu))
return 0; /* Idle CPUs are completely uninteresting. */
aperfmperf_snapshot_cpu(cpu, ktime_get(), true);
return per_cpu(samples.khz, cpu);
}
void arch_freq_prepare_all(void)
{
ktime_t now = ktime_get();
bool wait = false;
int cpu;
if (!cpu_khz)
return;
if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
return;
for_each_online_cpu(cpu) {
if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
continue;
if (rcu_is_idle_cpu(cpu))
continue; /* Idle CPUs are completely uninteresting. */
if (!aperfmperf_snapshot_cpu(cpu, now, false))
wait = true;
}
if (wait)
msleep(APERFMPERF_REFRESH_DELAY_MS);
}
unsigned int arch_freq_get_on_cpu(int cpu)
{
struct aperfmperf_sample *s = per_cpu_ptr(&samples, cpu);
if (!cpu_khz)
return 0;
if (!boot_cpu_has(X86_FEATURE_APERFMPERF))
return 0;
if (!housekeeping_cpu(cpu, HK_FLAG_MISC))
return 0;
if (aperfmperf_snapshot_cpu(cpu, ktime_get(), true))
return per_cpu(samples.khz, cpu);
msleep(APERFMPERF_REFRESH_DELAY_MS);
atomic_set(&s->scfpending, 1);
smp_mb(); /* ->scfpending before smp_call_function_single(). */
smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1);
return per_cpu(samples.khz, cpu);
}
|
