clock_bench.c

#include <time.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define N (1000000)

void clock_test(clockid_t clock, char *clock_str) {
    struct timespec ts, t0, t1;
    int r = clock_gettime(clock, &ts);
    if (r != 0) { printf("%-21: %s\n", clock_str, strerror(errno)); return; }

    clock_gettime(CLOCK_MONOTONIC, &t0);
    for(int i=0; i<N; i++) {
        clock_gettime(clock, &ts);
    }
    clock_gettime(CLOCK_MONOTONIC, &t1);
    double delta_ns = (t1.tv_sec - t0.tv_sec) * 1e9 +
        (t1.tv_nsec - t0.tv_nsec);
    double delta_ns_percall = delta_ns / N;

    printf("%-21s: %6.1fns percall\n", clock_str, delta_ns_percall);
}

#define CLOCK_TEST(arg) clock_test(arg, 6 + #arg)

int main() {
    CLOCK_TEST(CLOCK_REALTIME);
    CLOCK_TEST(CLOCK_REALTIME_ALARM);
    CLOCK_TEST(CLOCK_REALTIME_COARSE);
    CLOCK_TEST(CLOCK_TAI);
    CLOCK_TEST(CLOCK_MONOTONIC);
    CLOCK_TEST(CLOCK_MONOTONIC_COARSE);
    CLOCK_TEST(CLOCK_MONOTONIC_RAW);
    CLOCK_TEST(CLOCK_BOOTTIME);
    CLOCK_TEST(CLOCK_BOOTTIME_ALARM);
    CLOCK_TEST(CLOCK_PROCESS_CPUTIME_ID);
    CLOCK_TEST(CLOCK_THREAD_CPUTIME_ID);
    CLOCK_TEST(CLOCK_REALTIME);
}