源码地址：/Rtoax/test/blob/master/c/cpu/cpu_occupy-proc-stat.c
首先看一下文件"/proc/stat"
//"/proc/stat"//---------------------------------//user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice.//cpu 195044598 6619 410450970 967314001 64039 0 85058 394458 0 0//cpu0 48705507 1701 102480874 241499274 14130 0 82302 103069 0 0//cpu1 48866063 1895 102699462 241657644 15853 0 1245 97930 0 0//cpu2 48782413 1260 102714102 242031473 18001 0 790 96743 0 0//cpu3 48690614 1762 102556531 242125609 16054 0 720 96715 0 0
上面的数值依次为：user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice.
根据计算公式
(user + nice + system)/(user + nice + system + idle + iowait + irq + softirq)*100%
或者省去一些项
(user + nice + system)/(user + nice + system + idle)*100%
需要注意的是，我们需要统计一段时间的值来计算瞬时CPU利用率。那我们修改公式为：
[(user1 + nice1 + system1) - (user0 + nice0 + system0)]/[(user1 + nice1 + system1 + idle1) - (user0 + nice0 + system0 + idle0)]*100%
是不是很简单。下面给出完整的程序：
#include <stdio.h>#include <stdlib.h>#include <unistd.h>#define NR_CPU_CORES sysconf(_SC_NPROCESSORS_ONLN) //CPU核心总数struct __cpu_core_stat { //"/proc/stat"//---------------------------------//user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice.//cpu 195044598 6619 410450970 967314001 64039 0 85058 394458 0 0//cpu0 48705507 1701 102480874 241499274 14130 0 82302 103069 0 0//cpu1 48866063 1895 102699462 241657644 15853 0 1245 97930 0 0//cpu2 48782413 1260 102714102 242031473 18001 0 790 96743 0 0//cpu3 48690614 1762 102556531 242125609 16054 0 720 96715 0 0long double user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice;};struct __cpu_core_stat_pair {struct __cpu_core_stat stat[2]; //0-start, 1-endstruct {int integer, decimal;}occupy;// long double occupy;};struct cpu_cores_occupy {int nr_cpu_core;struct __cpu_core_stat_pair *cpus_stat;};static int cpu_cores_occupy_init(struct cpu_cores_occupy *cco){if(!cco)return -1;cco->nr_cpu_core = NR_CPU_CORES;cco->cpus_stat = malloc(sizeof(struct __cpu_core_stat_pair)*(NR_CPU_CORES+1));return 0;}static int __cpu_cores_occupy_get(struct cpu_cores_occupy *cco, int stat_idx/*0-start, 1-end*/){int icore = 0;FILE *fp;struct __cpu_core_stat_pair *cpus_stat = cco->cpus_stat;fp = fopen("/proc/stat","r");for(icore=0;icore<=cco->nr_cpu_core;icore++) {fscanf(fp,"%*s %Lf %Lf %Lf %Lf %Lf %Lf %Lf %Lf %Lf %Lf",&cpus_stat[icore].stat[stat_idx].user, &cpus_stat[icore].stat[stat_idx].nice, &cpus_stat[icore].stat[stat_idx].system, &cpus_stat[icore].stat[stat_idx].idle, &cpus_stat[icore].stat[stat_idx].iowait, &cpus_stat[icore].stat[stat_idx].irq, &cpus_stat[icore].stat[stat_idx].softirq, &cpus_stat[icore].stat[stat_idx].steal, &cpus_stat[icore].stat[stat_idx].guest, &cpus_stat[icore].stat[stat_idx].guest_nice);}fclose(fp);}static int cpu_cores_occupy_getstart(struct cpu_cores_occupy *cco){return __cpu_cores_occupy_get(cco, 0);}static int cpu_cores_occupy_getend(struct cpu_cores_occupy *cco){return __cpu_cores_occupy_get(cco, 1);}static int cpu_cores_occupy_call(struct cpu_cores_occupy *cco){int icore = 0, idx;struct __cpu_core_stat_pair *cpus_stat = cco->cpus_stat;for(icore=0;icore<=cco->nr_cpu_core;icore++) {struct __cpu_core_stat *s0 = &cpus_stat[icore].stat[0];struct __cpu_core_stat *s1 = &cpus_stat[icore].stat[1];long double s0_0 = (s0->user+s0->nice+s0->system);long double s1_0 = (s1->user+s1->nice+s1->system);long double s0_1 = (s0->user+s0->nice+s0->system+s0->idle);long double s1_1 = (s1->user+s1->nice+s1->system+s1->idle);long double occupy = (s1_0 - s0_0) / (s1_1 - s0_1);cpus_stat[icore].occupy.integer = (int)(occupy*100);cpus_stat[icore].occupy.decimal = (int)(occupy*10000);// printf("cpu%d %Lf = (%Lf - %Lf) / (%Lf - %Lf)\n", icore-1, cpus_stat[icore].occupy, s1_0, s0_0, s1_1, s0_1); }}static int cpu_cores_occupy_display(struct cpu_cores_occupy *cco){int icore = 0;struct __cpu_core_stat_pair *cpus_stat = cco->cpus_stat;system("clear");for(icore=0;icore<=cco->nr_cpu_core;icore++) {printf("cpu%d \t%3d.%-4d %%\n", icore-1,cpus_stat[icore].occupy.integer, cpus_stat[icore].occupy.decimal);}}int main(){struct cpu_cores_occupy cco;cpu_cores_occupy_init(&cco);for(;;){cpu_cores_occupy_getstart(&cco);sleep(1);cpu_cores_occupy_getend(&cco);cpu_cores_occupy_call(&cco);cpu_cores_occupy_display(&cco);}}
开始运行
[root@localhost cpu]# ./a.out cpu-1 0.25 %cpu0 0.0 %cpu1 1.101 %cpu2 0.0 %cpu3 0.0 %
我们写一个有自旋锁死锁的程序，或者干脆一个while(1);并绑定核心运行，如下：
[root@localhost c]# taskset -c 1 ./a.out &[1] 182556[root@localhost c]# taskset -c 3 ./a.out &[2] 182569
结果如下：
即可看见CPU利用率100%的情况，然后我们用top指令验证一下：
确认无误，下班。
