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