[blue11]

Sorry to nitpick, but I believe the time difference code has an error of 1 millisecond 25% of the time:

    int64_t delta = tv2->tv_sec - tv1->tv_sec;
    return delta * 1000 + (tv2->tv_usec - tv1->tv_usec) / 1000;

One way to fix it is:

    int64_t deltasec = tv2->tv_sec - tv1->tv_sec - 1;
    int64_t deltausec = tv2->tv_usec - tv1->tv_usec + 1000000;
    return deltasec * 1000 + deltausec / 1000;

[fruneau]

The diff is a truncation. The actual error rate is 0.5ms on average. By using a round instead of truncation, we can reduce the error to 0.25ms on average.

[blue11]

Well, that much is obvious. But if you are going to truncate, you should be consistent. Always truncate towards 0, not sometimes towards 0 and sometimes towards infinity.