写一个程序，让控制cpu利用率在20%左右
思路很简单：每个循环控制sleep的时间占比

#include <iostream>
#include <chrono>
#include <unistd.h>

int main() {
    int ratio = 20;
    int base_time = 1000;
    int sleeptime = base_time * (100-ratio);
    int runtime = base_time * ratio;
    while(true) {
        auto start = std::chrono::high_resolution_clock::now();
        while(std::chrono::duration_cast<std::chrono::microseconds>(std::chrono::high_resolution_clock::now() - start).count() < runtime) {}
        usleep(sleeptime);
    }

    return 0;
}