/* * 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; 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 * @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_residency, last_idx = ldev->last_state_idx; int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0; int latency_req = cpuidle_governor_latency_req(dev->cpu); /* Special case when user has set very strict latency requirement */ if (unlikely(latency_req == 0)) { ladder_do_selection(ldev, last_idx, 0); return 0; } last_state = &ldev->states[last_idx]; last_residency = dev->last_residency - drv->states[last_idx].exit_latency; /* consider promotion */ if (last_idx < drv->state_count - 1 && !drv->states[last_idx + 1].disabled && !dev->states_usage[last_idx + 1].disable && last_residency > last_state->threshold.promotion_time && drv->states[last_idx + 1].exit_latency <= 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(ldev, last_idx, last_idx + 1); return last_idx + 1; } } /* consider demotion */ if (last_idx > first_idx && (drv->states[last_idx].disabled || dev->states_usage[last_idx].disable || drv->states[last_idx].exit_latency > latency_req)) { int i; for (i = last_idx - 1; i > first_idx; i--) { if (drv->states[i].exit_latency <= latency_req) break; } ladder_do_selection(ldev, last_idx, i); return i; } if (last_idx > first_idx && 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 * @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; ldev->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 = state->exit_latency; if (i > first_idx) lstate->threshold.demotion_time = state->exit_latency; } 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) { struct ladder_device *ldev = this_cpu_ptr(&ladder_devices); if (index > 0) ldev->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);