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
|
/*
* ladder.c - the residency ladder algorithm
*
* Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
* Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
* Copyright (C) 2004, 2005 Dominik Brodowski <linux@brodo.de>
*
* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
* Shaohua Li <shaohua.li@intel.com>
* Adam Belay <abelay@novell.com>
*
* This code is licenced under the GPL.
*/
#include <linux/kernel.h>
#include <linux/cpuidle.h>
#include <linux/jiffies.h>
#include <linux/tick.h>
#include <asm/io.h>
#include <linux/uaccess.h>
#define PROMOTION_COUNT 4
#define DEMOTION_COUNT 1
struct ladder_device_state {
struct {
u32 promotion_count;
u32 demotion_count;
u32 promotion_time;
u32 demotion_time;
} threshold;
struct {
int promotion_count;
int demotion_count;
} stats;
};
struct ladder_device {
struct ladder_device_state states[CPUIDLE_STATE_MAX];
int last_state_idx;
};
static DEFINE_PER_CPU(struct ladder_device, ladder_devices);
/**
* ladder_do_selection - prepares private data for a state change
* @ldev: the ladder device
* @old_idx: the current state index
* @new_idx: the new target state index
*/
static inline void ladder_do_selection(struct ladder_device *ldev,
int old_idx, int new_idx)
{
ldev->states[old_idx].stats.promotion_count = 0;
ldev->states[old_idx].stats.demotion_count = 0;
ldev->last_state_idx = new_idx;
}
/**
* ladder_select_state - selects the next state to enter
* @drv: cpuidle driver
* @dev: the CPU
* @dummy: not used
*/
static int ladder_select_state(struct cpuidle_driver *drv,
struct cpuidle_device *dev, bool *dummy)
{
struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
struct ladder_device_state *last_state;
int last_residency, last_idx = ldev->last_state_idx;
int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
int latency_req = cpuidle_governor_latency_req(dev->cpu);
/* Special case when user has set very strict latency requirement */
if (unlikely(latency_req == 0)) {
ladder_do_selection(ldev, last_idx, 0);
return 0;
}
last_state = &ldev->states[last_idx];
last_residency = dev->last_residency - drv->states[last_idx].exit_latency;
/* consider promotion */
if (last_idx < drv->state_count - 1 &&
!drv->states[last_idx + 1].disabled &&
!dev->states_usage[last_idx + 1].disable &&
last_residency > last_state->threshold.promotion_time &&
drv->states[last_idx + 1].exit_latency <= latency_req) {
last_state->stats.promotion_count++;
last_state->stats.demotion_count = 0;
if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
ladder_do_selection(ldev, last_idx, last_idx + 1);
return last_idx + 1;
}
}
/* consider demotion */
if (last_idx > first_idx &&
(drv->states[last_idx].disabled ||
dev->states_usage[last_idx].disable ||
drv->states[last_idx].exit_latency > latency_req)) {
int i;
for (i = last_idx - 1; i > first_idx; i--) {
if (drv->states[i].exit_latency <= latency_req)
break;
}
ladder_do_selection(ldev, last_idx, i);
return i;
}
if (last_idx > first_idx &&
last_residency < last_state->threshold.demotion_time) {
last_state->stats.demotion_count++;
last_state->stats.promotion_count = 0;
if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
ladder_do_selection(ldev, last_idx, last_idx - 1);
return last_idx - 1;
}
}
/* otherwise remain at the current state */
return last_idx;
}
/**
* ladder_enable_device - setup for the governor
* @drv: cpuidle driver
* @dev: the CPU
*/
static int ladder_enable_device(struct cpuidle_driver *drv,
struct cpuidle_device *dev)
{
int i;
int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
struct ladder_device_state *lstate;
struct cpuidle_state *state;
ldev->last_state_idx = first_idx;
for (i = first_idx; i < drv->state_count; i++) {
state = &drv->states[i];
lstate = &ldev->states[i];
lstate->stats.promotion_count = 0;
lstate->stats.demotion_count = 0;
lstate->threshold.promotion_count = PROMOTION_COUNT;
lstate->threshold.demotion_count = DEMOTION_COUNT;
if (i < drv->state_count - 1)
lstate->threshold.promotion_time = state->exit_latency;
if (i > first_idx)
lstate->threshold.demotion_time = state->exit_latency;
}
return 0;
}
/**
* ladder_reflect - update the correct last_state_idx
* @dev: the CPU
* @index: the index of actual state entered
*/
static void ladder_reflect(struct cpuidle_device *dev, int index)
{
struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
if (index > 0)
ldev->last_state_idx = index;
}
static struct cpuidle_governor ladder_governor = {
.name = "ladder",
.rating = 10,
.enable = ladder_enable_device,
.select = ladder_select_state,
.reflect = ladder_reflect,
};
/**
* init_ladder - initializes the governor
*/
static int __init init_ladder(void)
{
/*
* When NO_HZ is disabled, or when booting with nohz=off, the ladder
* governor is better so give it a higher rating than the menu
* governor.
*/
if (!tick_nohz_enabled)
ladder_governor.rating = 25;
return cpuidle_register_governor(&ladder_governor);
}
postcore_initcall(init_ladder);
|
