diff options
Diffstat (limited to 'drivers/cpuidle/governors/ladder.c')
| -rw-r--r-- | drivers/cpuidle/governors/ladder.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c new file mode 100644 index 000000000..8e9058c4e --- /dev/null +++ b/drivers/cpuidle/governors/ladder.c @@ -0,0 +1,197 @@ +/* + * 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; + u64 promotion_time_ns; + u64 demotion_time_ns; + } threshold; + struct { + int promotion_count; + int demotion_count; + } stats; +}; + +struct ladder_device { + struct ladder_device_state states[CPUIDLE_STATE_MAX]; +}; + +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 cpuidle_device *dev, + 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; + dev->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_idx = dev->last_state_idx; + int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0; + s64 latency_req = cpuidle_governor_latency_req(dev->cpu); + s64 last_residency; + + /* Special case when user has set very strict latency requirement */ + if (unlikely(latency_req == 0)) { + ladder_do_selection(dev, ldev, last_idx, 0); + return 0; + } + + last_state = &ldev->states[last_idx]; + + last_residency = dev->last_residency_ns - drv->states[last_idx].exit_latency_ns; + + /* consider promotion */ + if (last_idx < drv->state_count - 1 && + !dev->states_usage[last_idx + 1].disable && + last_residency > last_state->threshold.promotion_time_ns && + drv->states[last_idx + 1].exit_latency_ns <= 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(dev, ldev, last_idx, last_idx + 1); + return last_idx + 1; + } + } + + /* consider demotion */ + if (last_idx > first_idx && + (dev->states_usage[last_idx].disable || + drv->states[last_idx].exit_latency_ns > latency_req)) { + int i; + + for (i = last_idx - 1; i > first_idx; i--) { + if (drv->states[i].exit_latency_ns <= latency_req) + break; + } + ladder_do_selection(dev, ldev, last_idx, i); + return i; + } + + if (last_idx > first_idx && + last_residency < last_state->threshold.demotion_time_ns) { + 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(dev, 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; + + dev->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_ns = state->exit_latency_ns; + if (i > first_idx) + lstate->threshold.demotion_time_ns = state->exit_latency_ns; + } + + 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) +{ + if (index > 0) + dev->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); |