ARM双核平台下POSIX定时器引发总CPU负载异常过高问题

架构老林

2026-6-18

500us POSIX定时器引发系统总CPU负载异常飙升问题

现象描述

在双核ARM Cortex-A9处理器上运行含500us间隔POSIX定时器的测试程序timertest，进程自身CPU负载约25%，但系统总CPU负载有时会达到100%
终止该进程后，系统总CPU负载立即降至1%
替换为setitimer定时器，同时使用htop、procps-ng top等工具验证，现象完全一致
将定时器间隔调整为499us后，系统总CPU负载与进程负载匹配，约为24%

相关附件信息

测试代码

#include <stdio.h>
#include <signal.h>
#include <time.h>

static void timer_callback(int sig) {
    // 空回调，仅触发信号
}

int main(void) {
    timer_t timer_id;
    struct sigevent sev;
    struct itimerspec timer_spec;

    // 设置定时器通知方式为信号
    sev.sigev_notify = SIGEV_SIGNAL;
    sev.sigev_signo = SIGUSR1;
    sev.sigev_value.sival_ptr = &timer_id;
    signal(SIGUSR1, timer_callback);

    // 创建定时器
    if (timer_create(CLOCK_MONOTONIC, &sev, &timer_id) == -1) {
        perror("timer_create failed");
        return 1;
    }

    // 设置定时器间隔为500us
    timer_spec.it_value.tv_sec = 0;
    timer_spec.it_value.tv_nsec = 500 * 1000;
    timer_spec.it_interval = timer_spec.it_value;

    if (timer_settime(timer_id, 0, &timer_spec, NULL) == -1) {
        perror("timer_settime failed");
        return 1;
    }

    // 主循环挂起
    while (1) {
        pause();
    }

    return 0;
}