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
|
/*
* menu.c - the menu idle governor
*
* Copyright (C) 2006-2007 Adam Belay <abelay@novell.com>
*
* This code is licenced under the GPL.
*/
#include <linux/kernel.h>
#include <linux/cpuidle.h>
#include <linux/pm_qos_params.h>
#include <linux/time.h>
#include <linux/ktime.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
#define BREAK_FUZZ 4 /* 4 us */
struct menu_device {
int last_state_idx;
unsigned int expected_us;
unsigned int predicted_us;
unsigned int last_measured_us;
unsigned int elapsed_us;
};
static DEFINE_PER_CPU(struct menu_device, menu_devices);
/**
* menu_select - selects the next idle state to enter
* @dev: the CPU
*/
static int menu_select(struct cpuidle_device *dev)
{
struct menu_device *data = &__get_cpu_var(menu_devices);
int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
int i;
/* Special case when user has set very strict latency requirement */
if (unlikely(latency_req == 0)) {
data->last_state_idx = 0;
return 0;
}
/* determine the expected residency time */
data->expected_us =
(u32) ktime_to_ns(tick_nohz_get_sleep_length()) / 1000;
/* find the deepest idle state that satisfies our constraints */
for (i = CPUIDLE_DRIVER_STATE_START + 1; i < dev->state_count; i++) {
struct cpuidle_state *s = &dev->states[i];
if (s->target_residency > data->expected_us)
break;
if (s->target_residency > data->predicted_us)
break;
if (s->exit_latency > latency_req)
break;
}
data->last_state_idx = i - 1;
return i - 1;
}
/**
* menu_reflect - attempts to guess what happened after entry
* @dev: the CPU
*
* NOTE: it's important to be fast here because this operation will add to
* the overall exit latency.
*/
static void menu_reflect(struct cpuidle_device *dev)
{
struct menu_device *data = &__get_cpu_var(menu_devices);
int last_idx = data->last_state_idx;
unsigned int measured_us =
cpuidle_get_last_residency(dev) + data->elapsed_us;
struct cpuidle_state *target = &dev->states[last_idx];
/*
* Ugh, this idle state doesn't support residency measurements, so we
* are basically lost in the dark. As a compromise, assume we slept
* for one full standard timer tick. However, be aware that this
* could potentially result in a suboptimal state transition.
*/
if (!(target->flags & CPUIDLE_FLAG_TIME_VALID))
measured_us = USEC_PER_SEC / HZ;
/* Predict time remaining until next break event */
if (measured_us + BREAK_FUZZ < data->expected_us - target->exit_latency) {
data->predicted_us = max(measured_us, data->last_measured_us);
data->last_measured_us = measured_us;
data->elapsed_us = 0;
} else {
if (data->elapsed_us < data->elapsed_us + measured_us)
data->elapsed_us = measured_us;
else
data->elapsed_us = -1;
data->predicted_us = max(measured_us, data->last_measured_us);
}
}
/**
* menu_enable_device - scans a CPU's states and does setup
* @dev: the CPU
*/
static int menu_enable_device(struct cpuidle_device *dev)
{
struct menu_device *data = &per_cpu(menu_devices, dev->cpu);
memset(data, 0, sizeof(struct menu_device));
return 0;
}
static struct cpuidle_governor menu_governor = {
.name = "menu",
.rating = 20,
.enable = menu_enable_device,
.select = menu_select,
.reflect = menu_reflect,
.owner = THIS_MODULE,
};
/**
* init_menu - initializes the governor
*/
static int __init init_menu(void)
{
return cpuidle_register_governor(&menu_governor);
}
/**
* exit_menu - exits the governor
*/
static void __exit exit_menu(void)
{
cpuidle_unregister_governor(&menu_governor);
}
MODULE_LICENSE("GPL");
module_init(init_menu);
module_exit(exit_menu);
|
