158 lines
3.9 KiB
C
158 lines
3.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* haltpoll.c - haltpoll idle governor
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*
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* Copyright 2019 Red Hat, Inc. and/or its affiliates.
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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* Authors: Marcelo Tosatti <mtosatti@redhat.com>
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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/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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#include <linux/sched.h>
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#include <linux/module.h>
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#include <linux/kvm_para.h>
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#include <trace/events/power.h>
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static unsigned int guest_halt_poll_ns __read_mostly = 200000;
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module_param(guest_halt_poll_ns, uint, 0644);
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/* division factor to shrink halt_poll_ns */
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static unsigned int guest_halt_poll_shrink __read_mostly = 2;
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module_param(guest_halt_poll_shrink, uint, 0644);
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/* multiplication factor to grow per-cpu poll_limit_ns */
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static unsigned int guest_halt_poll_grow __read_mostly = 2;
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module_param(guest_halt_poll_grow, uint, 0644);
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/* value in us to start growing per-cpu halt_poll_ns */
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static unsigned int guest_halt_poll_grow_start __read_mostly = 50000;
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module_param(guest_halt_poll_grow_start, uint, 0644);
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/* allow shrinking guest halt poll */
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static bool guest_halt_poll_allow_shrink __read_mostly = true;
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module_param(guest_halt_poll_allow_shrink, bool, 0644);
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/**
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* haltpoll_select - selects the next idle state to enter
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* @drv: cpuidle driver containing state data
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* @dev: the CPU
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* @stop_tick: indication on whether or not to stop the tick
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*/
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static int haltpoll_select(struct cpuidle_driver *drv,
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struct cpuidle_device *dev,
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bool *stop_tick)
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{
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s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
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if (!drv->state_count || latency_req == 0) {
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*stop_tick = false;
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return 0;
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}
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if (dev->poll_limit_ns == 0)
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return 1;
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/* Last state was poll? */
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if (dev->last_state_idx == 0) {
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/* Halt if no event occurred on poll window */
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if (dev->poll_time_limit == true)
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return 1;
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*stop_tick = false;
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/* Otherwise, poll again */
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return 0;
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}
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*stop_tick = false;
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/* Last state was halt: poll */
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return 0;
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}
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static void adjust_poll_limit(struct cpuidle_device *dev, u64 block_ns)
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{
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unsigned int val;
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/* Grow cpu_halt_poll_us if
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* cpu_halt_poll_us < block_ns < guest_halt_poll_us
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*/
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if (block_ns > dev->poll_limit_ns && block_ns <= guest_halt_poll_ns) {
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val = dev->poll_limit_ns * guest_halt_poll_grow;
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if (val < guest_halt_poll_grow_start)
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val = guest_halt_poll_grow_start;
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if (val > guest_halt_poll_ns)
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val = guest_halt_poll_ns;
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trace_guest_halt_poll_ns_grow(val, dev->poll_limit_ns);
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dev->poll_limit_ns = val;
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} else if (block_ns > guest_halt_poll_ns &&
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guest_halt_poll_allow_shrink) {
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unsigned int shrink = guest_halt_poll_shrink;
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val = dev->poll_limit_ns;
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if (shrink == 0) {
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val = 0;
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} else {
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val /= shrink;
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/* Reset value to 0 if shrunk below grow_start */
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if (val < guest_halt_poll_grow_start)
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val = 0;
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}
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trace_guest_halt_poll_ns_shrink(val, dev->poll_limit_ns);
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dev->poll_limit_ns = val;
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}
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}
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/**
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* haltpoll_reflect - update variables and update poll time
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* @dev: the CPU
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* @index: the index of actual entered state
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*/
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static void haltpoll_reflect(struct cpuidle_device *dev, int index)
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{
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dev->last_state_idx = index;
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if (index != 0)
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adjust_poll_limit(dev, dev->last_residency_ns);
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}
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/**
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* haltpoll_enable_device - scans a CPU's states and does setup
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* @drv: cpuidle driver
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* @dev: the CPU
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*/
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static int haltpoll_enable_device(struct cpuidle_driver *drv,
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struct cpuidle_device *dev)
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{
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dev->poll_limit_ns = 0;
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return 0;
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}
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static struct cpuidle_governor haltpoll_governor = {
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.name = "haltpoll",
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.rating = 9,
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.enable = haltpoll_enable_device,
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.select = haltpoll_select,
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.reflect = haltpoll_reflect,
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};
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static int __init init_haltpoll(void)
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{
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if (kvm_para_available())
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return cpuidle_register_governor(&haltpoll_governor);
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return 0;
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}
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postcore_initcall(init_haltpoll);
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