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716ff71ae2
When a KVM guest has MWAIT, mwait_idle() is used as the default idle
function.
However, the cpuidle-haltpoll driver calls default_idle() from
default_enter_idle() directly and that one uses HLT instead of MWAIT,
which may affect performance adversely, because MWAIT is preferred to
HLT as explained by the changelog of commit aebef63cf7 ("x86: Remove
vendor checks from prefer_mwait_c1_over_halt").
Make default_enter_idle() call arch_cpu_idle(), which can use MWAIT,
instead of default_idle() to address this issue.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
[ rjw: Changelog rewrite ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
147 lines
3.1 KiB
C
147 lines
3.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* cpuidle driver for haltpoll 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/init.h>
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#include <linux/cpu.h>
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#include <linux/cpuidle.h>
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#include <linux/module.h>
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#include <linux/sched/idle.h>
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#include <linux/kvm_para.h>
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#include <linux/cpuidle_haltpoll.h>
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static bool force __read_mostly;
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module_param(force, bool, 0444);
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MODULE_PARM_DESC(force, "Load unconditionally");
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static struct cpuidle_device __percpu *haltpoll_cpuidle_devices;
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static enum cpuhp_state haltpoll_hp_state;
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static int default_enter_idle(struct cpuidle_device *dev,
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struct cpuidle_driver *drv, int index)
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{
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if (current_clr_polling_and_test()) {
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local_irq_enable();
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return index;
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}
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arch_cpu_idle();
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return index;
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}
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static struct cpuidle_driver haltpoll_driver = {
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.name = "haltpoll",
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.governor = "haltpoll",
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.states = {
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{ /* entry 0 is for polling */ },
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{
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.enter = default_enter_idle,
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.exit_latency = 1,
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.target_residency = 1,
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.power_usage = -1,
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.name = "haltpoll idle",
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.desc = "default architecture idle",
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},
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},
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.safe_state_index = 0,
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.state_count = 2,
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};
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static int haltpoll_cpu_online(unsigned int cpu)
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{
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struct cpuidle_device *dev;
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dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
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if (!dev->registered) {
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dev->cpu = cpu;
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if (cpuidle_register_device(dev)) {
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pr_notice("cpuidle_register_device %d failed!\n", cpu);
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return -EIO;
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}
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arch_haltpoll_enable(cpu);
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}
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return 0;
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}
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static int haltpoll_cpu_offline(unsigned int cpu)
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{
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struct cpuidle_device *dev;
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dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
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if (dev->registered) {
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arch_haltpoll_disable(cpu);
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cpuidle_unregister_device(dev);
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}
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return 0;
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}
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static void haltpoll_uninit(void)
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{
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if (haltpoll_hp_state)
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cpuhp_remove_state(haltpoll_hp_state);
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cpuidle_unregister_driver(&haltpoll_driver);
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free_percpu(haltpoll_cpuidle_devices);
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haltpoll_cpuidle_devices = NULL;
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}
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static bool haltpoll_want(void)
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{
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return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
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}
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static int __init haltpoll_init(void)
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{
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int ret;
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struct cpuidle_driver *drv = &haltpoll_driver;
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/* Do not load haltpoll if idle= is passed */
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if (boot_option_idle_override != IDLE_NO_OVERRIDE)
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return -ENODEV;
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if (!kvm_para_available() || !haltpoll_want())
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return -ENODEV;
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cpuidle_poll_state_init(drv);
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ret = cpuidle_register_driver(drv);
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if (ret < 0)
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return ret;
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haltpoll_cpuidle_devices = alloc_percpu(struct cpuidle_device);
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if (haltpoll_cpuidle_devices == NULL) {
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cpuidle_unregister_driver(drv);
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return -ENOMEM;
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}
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ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "cpuidle/haltpoll:online",
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haltpoll_cpu_online, haltpoll_cpu_offline);
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if (ret < 0) {
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haltpoll_uninit();
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} else {
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haltpoll_hp_state = ret;
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ret = 0;
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}
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return ret;
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}
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static void __exit haltpoll_exit(void)
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{
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haltpoll_uninit();
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}
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module_init(haltpoll_init);
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module_exit(haltpoll_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
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