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c1d51f684c
Currently, the cpuidle subsystem uses microseconds as the unit of time which (among other things) causes the idle loop to incur some integer division overhead for no clear benefit. In order to allow cpuidle to measure time in nanoseconds, add two new fields, exit_latency_ns and target_residency_ns, to represent the exit latency and target residency of an idle state in nanoseconds, respectively, to struct cpuidle_state and initialize them with the help of the corresponding values in microseconds provided by drivers. Additionally, change cpuidle_governor_latency_req() to return the idle state exit latency constraint in nanoseconds. Also meeasure idle state residency (last_residency_ns in struct cpuidle_device and time_ns in struct cpuidle_driver) in nanoseconds and update the cpuidle core and governors accordingly. However, the menu governor still computes typical intervals in microseconds to avoid integer overflows. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Doug Smythies <dsmythies@telus.net> Tested-by: Doug Smythies <dsmythies@telus.net>
150 lines
3.7 KiB
C
150 lines
3.7 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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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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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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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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