/* * 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/pm_qos_params.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; int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY); if (unlikely(!ldev)) return 0; /* 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]; 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 <= 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 > CPUIDLE_DRIVER_STATE_START && dev->states[last_idx].exit_latency > latency_req) { int i; for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) { if (dev->states[i].exit_latency <= latency_req) break; } ladder_do_selection(ldev, last_idx, i); return i; } if (last_idx > CPUIDLE_DRIVER_STATE_START && 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 = CPUIDLE_DRIVER_STATE_START; 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);