1328edca4a
The downside of guest side polling is that polling is performed even with other runnable tasks in the host. However, even if poll in kvm can aware whether or not other runnable tasks in the same pCPU, it can still incur extra overhead in over-subscribe scenario. Now we can just enable guest polling when dedicated pCPUs are available. Acked-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
135 lines
2.8 KiB
C
135 lines
2.8 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 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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default_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 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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cpuidle_poll_state_init(drv);
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if (!kvm_para_available() ||
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!kvm_para_has_hint(KVM_HINTS_REALTIME))
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return -ENODEV;
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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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