167 lines
4.2 KiB
C
167 lines
4.2 KiB
C
/*
|
|
* 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/latency.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;
|
|
|
|
if (unlikely(!ldev))
|
|
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 <= system_latency_constraint()) {
|
|
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 > 0 &&
|
|
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 = 0;
|
|
|
|
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);
|