linux系统下CPU利用率的计算

Posted 2022-11-20 我要出家当道士

目录

一、设计思路

二、参考代码

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一、设计思路

        思路很简单：主要通过解析 /proc/stat 文件中记录的 CPU 使用详情信息。内容如下：

$ cat /proc/stat
cpu  500 0 1148 37091 0 21 0 0 0 0
cpu0 46 0 193 4603 0 17 0 0 0 0
cpu1 17 0 34 4792 0 0 0 0 0 0
cpu2 198 0 171 4473 0 3 0 0 0 0
cpu3 21 0 20 4801 0 0 0 0 0 0
cpu4 96 0 331 4415 0 0 0 0 0 0
cpu5 34 0 82 4726 0 0 0 0 0 0
cpu6 62 0 128 4653 0 0 0 0 0 0
cpu7 26 0 189 4628 0 1 0 0 0 0
intr 894498 377553 332 0 0 0 0 0 0 0 287178 0 0 1078 0 8572 189 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ctxt 494453
btime 1658673908
processes 21
procs_running 1
procs_blocked 0
softirq 531871 0 166655 5588 285920 8660 0 272 0 791 63985

        该文件的第一行记录了 CPU 时间片的分布情况。字段依次为：

user	从系统启动开始累计到当前时刻，用户态的CPU时间，不包含nice值为负进程。
nice	从系统启动开始累计到当前时刻，nice值为负的进程所占用的CPU时间
system	从系统启动开始累计到当前时刻，核心时间
idle	从系统启动开始累计到当前时刻，除IO等待时间以外其它等待时间
iowait	从系统启动开始累计到当前时刻，IO等待时间
irq	从系统启动开始累计到当前时刻，硬中断时间
softirq	从系统启动开始累计到当前时刻，软中断时间

    CPU利用率 = 1 - （CPU空闲时间片 / CPU时间片总和）。

    CPU时间片总和 = user + nice + system + idle + iowait + irq + softirq

    CPU 空闲时间片 = idle

         需要注意的是，/proc/stat 文件中记录的时间都是自系统启动开始的累计时间，所以计算CPU的使用率需要依据一个时间间隔内的CPU时间片分布情况。

二、参考代码

        只是参考，肯定跑不起来的，缺了一些头文件。

typedef struct cpu_info_

    long time_user;
    long time_nice;
    long time_system;
    long time_idle;
    long time_iowait;
    long time_irq;
    long time_sirq;
cpu_info;

cpu_info *cpu_info_snap()

    char cmd[CMD_LEN_GER] = "cat /proc/stat", cpu_info_tmp[CMD_LEN_RES] = "", str_tmp[10] = "";
    FILE *file = popen(cmd, "r");
    if (file == NULL)
    
        LOG_FATAL("[CPU]-->cmd(%s) execute failed\\n", cmd);
        return NULL;
    
    cpu_info *cpu_time = (cpu_info *)malloc(sizeof(cpu_info));
    fgets(cpu_info_tmp, CMD_LEN_RES, file);
    sscanf(cpu_info_tmp, "%s %ld %ld %ld %ld %ld %ld %ld", str_tmp, &cpu_time->time_user, &cpu_time->time_nice, &cpu_time->time_system, 
                        &cpu_time->time_idle, &cpu_time->time_iowait, &cpu_time->time_irq, &cpu_time->time_sirq);
    return cpu_time;


long cpu_time_total(cpu_info *info)

    if (info == NULL)
    
        return ERROR;
    
    return info->time_user + info->time_nice + info->time_system + info->time_idle + info->time_iowait + info->time_irq + info->time_sirq;


int cpu_gen_info(char *cpu_info_str, int len, char *err)

    cpu_info *cpu_time_pre = cpu_info_snap();
    usleep(100*1000);
    cpu_info *cpu_time_back = cpu_info_snap();

    long ct_total_pre = cpu_time_total(cpu_time_pre), ct_total_back = cpu_time_total(cpu_time_back);
    if (ct_total_pre < 0 || ct_total_back < 0 || ct_total_pre >= ct_total_back)
    
        LOG_ERROR("[CPU]->cpu time format error! pre(%ld)--back(%ld)\\n", ct_total_pre, ct_total_back);
        return ERROR;
    

    long ct_idle_pre = cpu_time_pre->time_idle, ct_idle_back = cpu_time_back->time_idle;
    if(ct_idle_back <= ct_idle_pre)
    
        LOG_ERROR("[CPU]->cpu idle time fotmat errot! pre(%ld)--back(%ld)\\n", ct_idle_pre, ct_idle_back);
        return ERROR;
    

    int rate = (1 - (ct_idle_back * 1.0 - ct_idle_pre * 1.0) / (ct_total_back * 1.0 - ct_total_pre * 1.0)) * 100;
    printf("%d \\n", rate);

    free(cpu_time_pre);
    free(cpu_time_back);
    return OK;

        有什么不足欢迎提出来。