1 /*
2 * ladder.c - the residency ladder algorithm
3 *
4 * Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
5 * Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
6 * Copyright (C) 2004, 2005 Dominik Brodowski <linux@brodo.de>
7 *
8 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
9 * Shaohua Li <shaohua.li@intel.com>
10 * Adam Belay <abelay@novell.com>
11 *
12 * This code is licenced under the GPL.
13 */
14
15 #include <linux/kernel.h>
16 #include <linux/cpuidle.h>
17 #include <linux/pm_qos_params.h>
18 #include <linux/moduleparam.h>
19 #include <linux/jiffies.h>
20
21 #include <asm/io.h>
22 #include <asm/uaccess.h>
23
24 #define PROMOTION_COUNT 4
25 #define DEMOTION_COUNT 1
26
27 struct ladder_device_state {
28 struct {
29 u32 promotion_count;
30 u32 demotion_count;
31 u32 promotion_time;
32 u32 demotion_time;
33 } threshold;
34 struct {
35 int promotion_count;
36 int demotion_count;
37 } stats;
38 };
39
40 struct ladder_device {
41 struct ladder_device_state states[CPUIDLE_STATE_MAX];
42 int last_state_idx;
43 };
44
45 static DEFINE_PER_CPU(struct ladder_device, ladder_devices);
46
47 /**
48 * ladder_do_selection - prepares private data for a state change
49 * @ldev: the ladder device
50 * @old_idx: the current state index
51 * @new_idx: the new target state index
52 */
53 static inline void ladder_do_selection(struct ladder_device *ldev,
54 int old_idx, int new_idx)
55 {
56 ldev->states[old_idx].stats.promotion_count = 0;
57 ldev->states[old_idx].stats.demotion_count = 0;
58 ldev->last_state_idx = new_idx;
59 }
60
61 /**
62 * ladder_select_state - selects the next state to enter
63 * @dev: the CPU
64 */
65 static int ladder_select_state(struct cpuidle_device *dev)
66 {
67 struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
68 struct ladder_device_state *last_state;
69 int last_residency, last_idx = ldev->last_state_idx;
70
71 if (unlikely(!ldev))
72 return 0;
73
74 last_state = &ldev->states[last_idx];
75
76 if (dev->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID)
77 last_residency = cpuidle_get_last_residency(dev) - dev->states[last_idx].exit_latency;
78 else
79 last_residency = last_state->threshold.promotion_time + 1;
80
81 /* consider promotion */
82 if (last_idx < dev->state_count - 1 &&
83 last_residency > last_state->threshold.promotion_time &&
84 dev->states[last_idx + 1].exit_latency <=
85 pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY)) {
86 last_state->stats.promotion_count++;
87 last_state->stats.demotion_count = 0;
88 if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
89 ladder_do_selection(ldev, last_idx, last_idx + 1);
90 return last_idx + 1;
91 }
92 }
93
94 /* consider demotion */
95 if (last_idx > 0 &&
96 last_residency < last_state->threshold.demotion_time) {
97 last_state->stats.demotion_count++;
98 last_state->stats.promotion_count = 0;
99 if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
100 ladder_do_selection(ldev, last_idx, last_idx - 1);
101 return last_idx - 1;
102 }
103 }
104
105 /* otherwise remain at the current state */
106 return last_idx;
107 }
108
109 /**
110 * ladder_enable_device - setup for the governor
111 * @dev: the CPU
112 */
113 static int ladder_enable_device(struct cpuidle_device *dev)
114 {
115 int i;
116 struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
117 struct ladder_device_state *lstate;
118 struct cpuidle_state *state;
119
120 ldev->last_state_idx = 0;
121
122 for (i = 0; i < dev->state_count; i++) {
123 state = &dev->states[i];
124 lstate = &ldev->states[i];
125
126 lstate->stats.promotion_count = 0;
127 lstate->stats.demotion_count = 0;
128
129 lstate->threshold.promotion_count = PROMOTION_COUNT;
130 lstate->threshold.demotion_count = DEMOTION_COUNT;
131
132 if (i < dev->state_count - 1)
133 lstate->threshold.promotion_time = state->exit_latency;
134 if (i > 0)
135 lstate->threshold.demotion_time = state->exit_latency;
136 }
137
138 return 0;
139 }
140
141 static struct cpuidle_governor ladder_governor = {
142 .name = "ladder",
143 .rating = 10,
144 .enable = ladder_enable_device,
145 .select = ladder_select_state,
146 .owner = THIS_MODULE,
147 };
148
149 /**
150 * init_ladder - initializes the governor
151 */
152 static int __init init_ladder(void)
153 {
154 return cpuidle_register_governor(&ladder_governor);
155 }
156
157 /**
158 * exit_ladder - exits the governor
159 */
160 static void __exit exit_ladder(void)
161 {
162 cpuidle_unregister_governor(&ladder_governor);
163 }
164
165 MODULE_LICENSE("GPL");
166 module_init(init_ladder);
167 module_exit(exit_ladder);
168
|
This page was automatically generated by the
LXR engine.
|