error: ‘usleep’ was not declared in this scope

加上一个：  #include <unistd.h>  执行成功。
 

控制CPU代码：

#include <iostream>
#include <pthread.h>
#include <time.h>
#include <math.h>
#include <unistd.h>
using namespace std;

typedef long long int int64;
const int NUM_THREADS = 24; // CPU 核数
int eachTime = 100;
int cpuinfo = 0; // 占用率

int64 GetTickCount()
{
    timespec now;
    clock_gettime(CLOCK_MONOTONIC, &now);
    int64 sec = now.tv_sec;
    int64 nsec = now.tv_nsec;
    return sec*1000 + nsec/1000000;
}

void* CPUCost(void *args)
{
    std::cout << "XXXX CPUCost" << std::endl;
    int busyTime = eachTime * cpuinfo / 100;
    //std::cout << "XXXX cpuinfo = " << cpuinfo << std::endl;
    int idleTime = eachTime - busyTime;
    int64 startTime = 0;
    while (true)
    {
        startTime = GetTickCount();
        while((GetTickCount() - startTime) <= busyTime)
        {
            ;
        }

        usleep(100);
    }
}

int main(int argc, char **argv)
{
    std::cin >> cpuinfo;
    pthread_t t[NUM_THREADS];
    for(int i = 0; i < NUM_THREADS; i++)
    {
        int ret = pthread_create(&t[i], NULL, CPUCost, NULL);
        if(ret)
         {
             std::cout << "XXXX create err" << std::endl;
         }
    }

    pthread_exit(NULL);

    return 0;
}