a2bd920233
poll_idle was added to CPUIDLE, just as a low latency idle handler, to be used in cases when user desires CPUs not to enter any idle state at all. It was supposed to be a run time idle=poll option to the user. But, it was indeed getting used during normal menu and ladder governor default case, with no special user setting (Reported by Linus Torvalds). Change below ensures that poll_idle will not be used unless user explicitly asks pm_qos infrastructure for zero latency requirement. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Andi Kleen <ak@linux.intel.com>
145 lines
3.5 KiB
C
145 lines
3.5 KiB
C
/*
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* menu.c - the menu idle governor
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*
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* Copyright (C) 2006-2007 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/time.h>
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#include <linux/ktime.h>
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#include <linux/hrtimer.h>
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#include <linux/tick.h>
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#define BREAK_FUZZ 4 /* 4 us */
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struct menu_device {
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int last_state_idx;
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unsigned int expected_us;
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unsigned int predicted_us;
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unsigned int last_measured_us;
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unsigned int elapsed_us;
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};
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static DEFINE_PER_CPU(struct menu_device, menu_devices);
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/**
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* menu_select - selects the next idle state to enter
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* @dev: the CPU
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*/
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static int menu_select(struct cpuidle_device *dev)
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{
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struct menu_device *data = &__get_cpu_var(menu_devices);
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int latency_req = pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY);
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int i;
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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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data->last_state_idx = 0;
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return 0;
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}
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/* determine the expected residency time */
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data->expected_us =
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(u32) ktime_to_ns(tick_nohz_get_sleep_length()) / 1000;
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/* find the deepest idle state that satisfies our constraints */
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for (i = CPUIDLE_DRIVER_STATE_START + 1; i < dev->state_count; i++) {
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struct cpuidle_state *s = &dev->states[i];
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if (s->target_residency > data->expected_us)
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break;
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if (s->target_residency > data->predicted_us)
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break;
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if (s->exit_latency > latency_req)
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break;
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}
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data->last_state_idx = i - 1;
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return i - 1;
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}
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/**
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* menu_reflect - attempts to guess what happened after entry
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* @dev: the CPU
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*
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* NOTE: it's important to be fast here because this operation will add to
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* the overall exit latency.
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*/
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static void menu_reflect(struct cpuidle_device *dev)
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{
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struct menu_device *data = &__get_cpu_var(menu_devices);
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int last_idx = data->last_state_idx;
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unsigned int measured_us =
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cpuidle_get_last_residency(dev) + data->elapsed_us;
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struct cpuidle_state *target = &dev->states[last_idx];
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/*
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* Ugh, this idle state doesn't support residency measurements, so we
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* are basically lost in the dark. As a compromise, assume we slept
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* for one full standard timer tick. However, be aware that this
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* could potentially result in a suboptimal state transition.
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*/
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if (!(target->flags & CPUIDLE_FLAG_TIME_VALID))
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measured_us = USEC_PER_SEC / HZ;
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/* Predict time remaining until next break event */
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if (measured_us + BREAK_FUZZ < data->expected_us - target->exit_latency) {
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data->predicted_us = max(measured_us, data->last_measured_us);
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data->last_measured_us = measured_us;
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data->elapsed_us = 0;
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} else {
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if (data->elapsed_us < data->elapsed_us + measured_us)
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data->elapsed_us = measured_us;
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else
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data->elapsed_us = -1;
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data->predicted_us = max(measured_us, data->last_measured_us);
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}
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}
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/**
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* menu_enable_device - scans a CPU's states and does setup
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* @dev: the CPU
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*/
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static int menu_enable_device(struct cpuidle_device *dev)
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{
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struct menu_device *data = &per_cpu(menu_devices, dev->cpu);
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memset(data, 0, sizeof(struct menu_device));
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return 0;
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}
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static struct cpuidle_governor menu_governor = {
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.name = "menu",
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.rating = 20,
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.enable = menu_enable_device,
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.select = menu_select,
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.reflect = menu_reflect,
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.owner = THIS_MODULE,
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};
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/**
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* init_menu - initializes the governor
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*/
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static int __init init_menu(void)
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{
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return cpuidle_register_governor(&menu_governor);
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}
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/**
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* exit_menu - exits the governor
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*/
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static void __exit exit_menu(void)
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{
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cpuidle_unregister_governor(&menu_governor);
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}
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MODULE_LICENSE("GPL");
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module_init(init_menu);
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module_exit(exit_menu);
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