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![venkatesh.pallipadi@intel.com](/assets/img/avatar_default.png)
ladder governor only honored latency requirement when promoting C-states. Instead. it should check for latency requirement on each idle call, and demote to appropriate C-state when there is a latency requirement change. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
185 lines
4.7 KiB
C
185 lines
4.7 KiB
C
/*
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* ladder.c - the residency ladder algorithm
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*
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* Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
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* Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
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* Copyright (C) 2004, 2005 Dominik Brodowski <linux@brodo.de>
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*
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* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
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* Shaohua Li <shaohua.li@intel.com>
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* Adam Belay <abelay@novell.com>
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*
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* This code is licenced under the GPL.
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*/
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#include <linux/kernel.h>
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#include <linux/cpuidle.h>
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#include <linux/pm_qos_params.h>
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#include <linux/moduleparam.h>
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#include <linux/jiffies.h>
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#include <asm/io.h>
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#include <asm/uaccess.h>
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#define PROMOTION_COUNT 4
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#define DEMOTION_COUNT 1
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struct ladder_device_state {
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struct {
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u32 promotion_count;
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u32 demotion_count;
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u32 promotion_time;
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u32 demotion_time;
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} threshold;
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struct {
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int promotion_count;
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int demotion_count;
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} stats;
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};
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struct ladder_device {
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struct ladder_device_state states[CPUIDLE_STATE_MAX];
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int last_state_idx;
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};
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static DEFINE_PER_CPU(struct ladder_device, ladder_devices);
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/**
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* ladder_do_selection - prepares private data for a state change
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* @ldev: the ladder device
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* @old_idx: the current state index
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* @new_idx: the new target state index
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*/
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static inline void ladder_do_selection(struct ladder_device *ldev,
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int old_idx, int new_idx)
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{
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ldev->states[old_idx].stats.promotion_count = 0;
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ldev->states[old_idx].stats.demotion_count = 0;
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ldev->last_state_idx = new_idx;
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}
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/**
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* ladder_select_state - selects the next state to enter
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* @dev: the CPU
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*/
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static int ladder_select_state(struct cpuidle_device *dev)
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{
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struct ladder_device *ldev = &__get_cpu_var(ladder_devices);
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struct ladder_device_state *last_state;
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int last_residency, last_idx = ldev->last_state_idx;
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int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
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if (unlikely(!ldev))
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return 0;
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/* Special case when user has set very strict latency requirement */
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if (unlikely(latency_req == 0)) {
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ladder_do_selection(ldev, last_idx, 0);
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return 0;
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}
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last_state = &ldev->states[last_idx];
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if (dev->states[last_idx].flags & CPUIDLE_FLAG_TIME_VALID)
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last_residency = cpuidle_get_last_residency(dev) - dev->states[last_idx].exit_latency;
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else
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last_residency = last_state->threshold.promotion_time + 1;
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/* consider promotion */
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if (last_idx < dev->state_count - 1 &&
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last_residency > last_state->threshold.promotion_time &&
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dev->states[last_idx + 1].exit_latency <= latency_req) {
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last_state->stats.promotion_count++;
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last_state->stats.demotion_count = 0;
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if (last_state->stats.promotion_count >= last_state->threshold.promotion_count) {
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ladder_do_selection(ldev, last_idx, last_idx + 1);
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return last_idx + 1;
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}
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}
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/* consider demotion */
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if (last_idx > CPUIDLE_DRIVER_STATE_START &&
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dev->states[last_idx].exit_latency > latency_req) {
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int i;
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for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
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if (dev->states[i].exit_latency <= latency_req)
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break;
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}
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ladder_do_selection(ldev, last_idx, i);
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return i;
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}
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if (last_idx > CPUIDLE_DRIVER_STATE_START &&
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last_residency < last_state->threshold.demotion_time) {
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last_state->stats.demotion_count++;
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last_state->stats.promotion_count = 0;
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if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
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ladder_do_selection(ldev, last_idx, last_idx - 1);
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return last_idx - 1;
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}
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}
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/* otherwise remain at the current state */
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return last_idx;
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}
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/**
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* ladder_enable_device - setup for the governor
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* @dev: the CPU
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*/
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static int ladder_enable_device(struct cpuidle_device *dev)
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{
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int i;
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struct ladder_device *ldev = &per_cpu(ladder_devices, dev->cpu);
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struct ladder_device_state *lstate;
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struct cpuidle_state *state;
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ldev->last_state_idx = CPUIDLE_DRIVER_STATE_START;
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for (i = 0; i < dev->state_count; i++) {
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state = &dev->states[i];
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lstate = &ldev->states[i];
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lstate->stats.promotion_count = 0;
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lstate->stats.demotion_count = 0;
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lstate->threshold.promotion_count = PROMOTION_COUNT;
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lstate->threshold.demotion_count = DEMOTION_COUNT;
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if (i < dev->state_count - 1)
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lstate->threshold.promotion_time = state->exit_latency;
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if (i > 0)
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lstate->threshold.demotion_time = state->exit_latency;
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}
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return 0;
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}
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static struct cpuidle_governor ladder_governor = {
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.name = "ladder",
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.rating = 10,
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.enable = ladder_enable_device,
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.select = ladder_select_state,
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.owner = THIS_MODULE,
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};
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/**
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* init_ladder - initializes the governor
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*/
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static int __init init_ladder(void)
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{
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return cpuidle_register_governor(&ladder_governor);
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}
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/**
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* exit_ladder - exits the governor
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*/
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static void __exit exit_ladder(void)
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{
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cpuidle_unregister_governor(&ladder_governor);
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}
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MODULE_LICENSE("GPL");
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module_init(init_ladder);
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module_exit(exit_ladder);
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