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Diffstat (limited to 'drivers/cpuidle/governors/ladder.c')
| -rw-r--r-- | drivers/cpuidle/governors/ladder.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c new file mode 100644 index 000000000000..eb666ecae7c9 --- /dev/null +++ b/drivers/cpuidle/governors/ladder.c @@ -0,0 +1,166 @@ +/* + * 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/latency.h> +#include <linux/moduleparam.h> +#include <linux/jiffies.h> + +#include <asm/io.h> +#include <asm/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 + * @dev: the CPU + */ +static int ladder_select_state(struct cpuidle_device *dev) +{ + struct ladder_device *ldev = &__get_cpu_var(ladder_devices); + struct ladder_device_state *last_state; + int last_residency, last_idx = ldev->last_state_idx; + + if (unlikely(!ldev)) + return 0; + + last_state = &ldev->states[last_idx]; + + if (dev->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID) + last_residency = cpuidle_get_last_residency(dev) - dev->states[last_idx].exit_latency; + else + last_residency = last_state->threshold.promotion_time + 1; + + /* consider promotion */ + if (last_idx < dev->state_count - 1 && + last_residency > last_state->threshold.promotion_time && + dev->states[last_idx + 1].exit_latency <= system_latency_constraint()) { + 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 > 0 && + 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 + * @dev: the CPU + */ +static int ladder_enable_device(struct cpuidle_device *dev) +{ + int i; + struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu); + struct ladder_device_state *lstate; + struct cpuidle_state *state; + + ldev->last_state_idx = 0; + + for (i = 0; i < dev->state_count; i++) { + state = &dev->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 < dev->state_count - 1) + lstate->threshold.promotion_time = state->exit_latency; + if (i > 0) + lstate->threshold.demotion_time = state->exit_latency; + } + + return 0; +} + +static struct cpuidle_governor ladder_governor = { + .name = "ladder", + .rating = 10, + .enable = ladder_enable_device, + .select = ladder_select_state, + .owner = THIS_MODULE, +}; + +/** + * init_ladder - initializes the governor + */ +static int __init init_ladder(void) +{ + return cpuidle_register_governor(&ladder_governor); +} + +/** + * exit_ladder - exits the governor + */ +static void __exit exit_ladder(void) +{ + cpuidle_unregister_governor(&ladder_governor); +} + +MODULE_LICENSE("GPL"); +module_init(init_ladder); +module_exit(exit_ladder); |