diff options
Diffstat (limited to 'drivers/cpuidle/governors/menu.c')
| -rw-r--r-- | drivers/cpuidle/governors/menu.c | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c new file mode 100644 index 0000000..299d45c --- /dev/null +++ b/drivers/cpuidle/governors/menu.c @@ -0,0 +1,137 @@ +/* + * 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/latency.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 i; + + /* 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 = 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 > system_latency_constraint()) + 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); |