考虑以下代码：

#include <stdio.h>
#include <time.h>
#include <math.h>

// Compile with gcc -lrt -lm -o test_clock test_clock.c

#define CLOCK CLOCK_MONOTONIC

int main(int argc, char** argv) {
    double temp, elapsed;
    int j;
    struct timespec requestStart, requestEnd, req;

    // Pseudo-sleep
    clock_gettime(CLOCK, &requestStart);
    temp = 0;
    for(j=0; j < 40; j++)
        temp += sin(j);
    clock_gettime(CLOCK, &requestEnd);
    elapsed = ( requestEnd.tv_sec - requestStart.tv_sec ) / 1e-6
                 + ( requestEnd.tv_nsec - requestStart.tv_nsec ) / 1e3;
    printf("Elapsed: %lf us\n", elapsed);

    // Nanosleep
    clock_gettime(CLOCK, &requestStart);
    req.tv_nsec = 5000;
    req.tv_sec = 0;
    clock_nanosleep(CLOCK, 0, &req, NULL);
    clock_gettime(CLOCK, &requestEnd);
    elapsed = ( requestEnd.tv_sec - requestStart.tv_sec ) / 1e-6
                 + ( requestEnd.tv_nsec - requestStart.tv_nsec ) / 1e3;

    printf("Elapsed: %lf us\n", elapsed);

}

在我的2.6.32系统上，结果是

Elapsed: 5.308000 us
Elapsed: 69.142000 us

我同意这很可能是因为nanosleep（）要求内核重新安排进程。如何避免这种情况？我想保留对CPU的所有权，并在精确的时间内闲置。