Len Brown | 4f86d3a | 2007-10-03 18:58:00 -0400 | [diff] [blame] | 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/latency.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 <= system_latency_constraint()) { |
| 85 | last_state->stats.promotion_count++; |
| 86 | last_state->stats.demotion_count = 0; |
| 87 | if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) { |
| 88 | ladder_do_selection(ldev, last_idx, last_idx + 1); |
| 89 | return last_idx + 1; |
| 90 | } |
| 91 | } |
| 92 | |
| 93 | /* consider demotion */ |
| 94 | if (last_idx > 0 && |
| 95 | last_residency < last_state->threshold.demotion_time) { |
| 96 | last_state->stats.demotion_count++; |
| 97 | last_state->stats.promotion_count = 0; |
| 98 | if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) { |
| 99 | ladder_do_selection(ldev, last_idx, last_idx - 1); |
| 100 | return last_idx - 1; |
| 101 | } |
| 102 | } |
| 103 | |
| 104 | /* otherwise remain at the current state */ |
| 105 | return last_idx; |
| 106 | } |
| 107 | |
| 108 | /** |
| 109 | * ladder_enable_device - setup for the governor |
| 110 | * @dev: the CPU |
| 111 | */ |
| 112 | static int ladder_enable_device(struct cpuidle_device *dev) |
| 113 | { |
| 114 | int i; |
| 115 | struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu); |
| 116 | struct ladder_device_state *lstate; |
| 117 | struct cpuidle_state *state; |
| 118 | |
| 119 | ldev->last_state_idx = 0; |
| 120 | |
| 121 | for (i = 0; i < dev->state_count; i++) { |
| 122 | state = &dev->states[i]; |
| 123 | lstate = &ldev->states[i]; |
| 124 | |
| 125 | lstate->stats.promotion_count = 0; |
| 126 | lstate->stats.demotion_count = 0; |
| 127 | |
| 128 | lstate->threshold.promotion_count = PROMOTION_COUNT; |
| 129 | lstate->threshold.demotion_count = DEMOTION_COUNT; |
| 130 | |
| 131 | if (i < dev->state_count - 1) |
| 132 | lstate->threshold.promotion_time = state->exit_latency; |
| 133 | if (i > 0) |
| 134 | lstate->threshold.demotion_time = state->exit_latency; |
| 135 | } |
| 136 | |
| 137 | return 0; |
| 138 | } |
| 139 | |
| 140 | static struct cpuidle_governor ladder_governor = { |
| 141 | .name = "ladder", |
| 142 | .rating = 10, |
| 143 | .enable = ladder_enable_device, |
| 144 | .select = ladder_select_state, |
| 145 | .owner = THIS_MODULE, |
| 146 | }; |
| 147 | |
| 148 | /** |
| 149 | * init_ladder - initializes the governor |
| 150 | */ |
| 151 | static int __init init_ladder(void) |
| 152 | { |
| 153 | return cpuidle_register_governor(&ladder_governor); |
| 154 | } |
| 155 | |
| 156 | /** |
| 157 | * exit_ladder - exits the governor |
| 158 | */ |
| 159 | static void __exit exit_ladder(void) |
| 160 | { |
| 161 | cpuidle_unregister_governor(&ladder_governor); |
| 162 | } |
| 163 | |
| 164 | MODULE_LICENSE("GPL"); |
| 165 | module_init(init_ladder); |
| 166 | module_exit(exit_ladder); |