【cpufreq】【governor】【performance】

最新推荐文章于 2024-08-14 15:19:08 发布

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最新推荐文章于 2024-08-14 15:19:08 发布

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本文深入探讨了Linux内核中的cpufreq性能调度器的工作原理，重点介绍了如何通过设置CPU频率为最大值来实现高性能模式，并详细展示了相关的核心代码。

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cpufreq的governor中performance实际上是最简单粗暴的，因为他直接将freq上升到最高

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/module.h>

// 回调函数响应具体的事件
static int cpufreq_governor_performance(struct cpufreq_policy *policy,
					unsigned int event)
{
	switch (event) {
	case CPUFREQ_GOV_START:
	case CPUFREQ_GOV_LIMITS:
		pr_debug("setting to %u kHz because of event %u\n", policy->max, event);
		__cpufreq_driver_target(policy, policy->max,CPUFREQ_RELATION_H);
		break;
	default:
		break;
	}
	return 0;
}

#ifdef CONFIG_CPU_FREQ_GOV_PERFORMANCE_MODULE
static
#endif
struct cpufreq_governor cpufreq_gov_performance = {
	.name		= "performance",
	.governor	= cpufreq_governor_performance,
	.owner		= THIS_MODULE,
};

static int __init cpufreq_gov_performance_init(void)
{
	return cpufreq_register_governor(&cpufreq_gov_performance);
}

static void __exit cpufreq_gov_performance_exit(void)
{
	cpufreq_unregister_governor(&cpufreq_gov_performance);
}

MODULE_AUTHOR("xxxxxx");
MODULE_DESCRIPTION("CPUfreq policy governor 'performance'");
MODULE_LICENSE("GPL");

// 序号是5
fs_initcall(cpufreq_gov_performance_init);
module_exit(cpufreq_gov_performance_exit);

注册和移除governor都是添加或者从内核的链表中添加或者移除

//将governor注册到cpufreq core中之后才能通过policy的governor和policy相互关联，才能被使用
int cpufreq_register_governor(struct cpufreq_governor *governor)
{
	int err;

	if (!governor)
		return -EINVAL;

	if (cpufreq_disabled())
		return -ENODEV;

	// mutex互斥体用来保护较长的临界区
	mutex_lock(&cpufreq_governor_mutex);

	governor->initialized = 0;
	err = -EBUSY;
	if (!find_governor(governor->name)) {
		err = 0;
		// 将governor添加到governor的list里面去
		// 核心层定义了一个全局链表变量，cpufreq_governor_list
		list_add(&governor->governor_list, &cpufreq_governor_list);
	}

	mutex_unlock(&cpufreq_governor_mutex);
	return err;
}
EXPORT_SYMBOL_GPL(cpufreq_register_governor);


void cpufreq_unregister_governor(struct cpufreq_governor *governor)
{
	struct cpufreq_policy *policy;
	unsigned long flags;

	if (!governor)
		return;

	if (cpufreq_disabled())
		return;

	/* clear last_governor for all inactive policies */
	read_lock_irqsave(&cpufreq_driver_lock, flags);
	for_each_inactive_policy(policy) {
		if (!strcmp(policy->last_governor, governor->name)) {
			policy->governor = NULL;
			strcpy(policy->last_governor, "\0");
		}
	}
	read_unlock_irqrestore(&cpufreq_driver_lock, flags);

	mutex_lock(&cpufreq_governor_mutex);
	list_del(&governor->governor_list);
	mutex_unlock(&cpufreq_governor_mutex);
	return;
}
EXPORT_SYMBOL_GPL(cpufreq_unregister_governor);

至于后面的接受事件的回调函数。。。