linux下usleep函数对CPU占用率的影响

linux下usleep函数对CPU占用率的影响

2023-11-16

环境

系统: ubuntu 22.04
内核版本: Linux 5.15.0-58-generic
cpu: Intel(R) Xeon(R) Platinum 8269CY CPU @ 2.50GHz
cpu核数: 1
架构: x86_64
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1. 测试代码

main.cpp

#include  // usleep

#define SLEEP_US 1

int main()
{
    while (1)
    {
        usleep(SLEEP_US);
    }

    return 0;
}
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$ g++ main.cpp -o main
$ ./main
$ top -p `pidof main`
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2. CPU占用率

不使用usleep延时

CPU占用率：95.3%

$ top -p `pidof main`
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
2325638 root      20   0    2640    940    848 R  95.3   0.1   0:29.17 main
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#define SLEEP_US 1 (1微秒)

CPU占用率：8.0%

$ top -p `pidof main`
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
2324270 root      20   0    2640    928    840 R   8.0   0.1   0:07.92 main
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#define SLEEP_US 10 (10微秒)

CPU占用率：7.0%

$ top -p `pidof main`
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
2326872 root      20   0    2640    976    888 R   7.0   0.1   0:01.61 main
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#define SLEEP_US 100 (100微秒)

CPU占用率：3.3%

$ top -p `pidof main`
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
2327593 root      20   0    2640    988    900 R   3.3   0.1   0:00.73 main
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#define SLEEP_US 1000 (1000微秒=1毫秒)

CPU占用率：0.7%

$ top -p `pidof main`
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
2328327 root      20   0    2640    984    896 S   0.7   0.1   0:00.15 main
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#define SLEEP_US 10000 (10000微秒=10毫秒)

CPU占用率：0.3%

$ top -p `pidof main`
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
2329099 root      20   0    2640    988    900 S   0.3   0.1   0:00.02 main
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#define SLEEP_US 100000 (100000微秒=100毫秒)

CPU占用率：0.0%

$ top -p `pidof main`
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
2329719 root      20   0    2640    984    896 S   0.0   0.1   0:00.00 main
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License

License under CC BY-NC-ND 4.0: 署名-非商业使用-禁止演绎

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Reference:
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