Calculates average time required to get the current time from the system in nanoseconds (from pmem/pmdk)

benchmark_time.c

#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#define NSECPSEC 1000000000

/*
 * benchmark_time.c -- benchmark_time module definitions
 */

typedef struct timespec benchmark_time_t;

void benchmark_time_get(benchmark_time_t *time);
void benchmark_time_diff(benchmark_time_t *d, benchmark_time_t *t1,
                         benchmark_time_t *t2);
double benchmark_time_get_secs(benchmark_time_t *t);
unsigned long long benchmark_time_get_nsecs(benchmark_time_t *t);
int benchmark_time_compare(const benchmark_time_t *t1,
                           const benchmark_time_t *t2);
void benchmark_time_set(benchmark_time_t *time, unsigned long long nsecs);
unsigned long long benchmark_get_avg_get_time(void);

/*
 * os_clock_gettime -- clock_gettime abstraction layer
 */
static int
os_clock_gettime(int id, struct timespec *ts)
{
    return clock_gettime(id, ts);
}

static void print_timespec(benchmark_time_t *diff, const char *name)
{
    printf("%s.tv_sec=%ld  %s.tv_nsec=%ld\n", name, diff->tv_sec, name, diff->tv_nsec);
}

/*
 * benchmark_time_get -- get timestamp from clock source
 */
void
benchmark_time_get(benchmark_time_t *time)
{
    os_clock_gettime(CLOCK_MONOTONIC, time);
}

/*
 * benchmark_time_diff -- get time interval
 */
void
benchmark_time_diff(benchmark_time_t *d, benchmark_time_t *t1,
                    benchmark_time_t *t2)
{
#ifdef DEBUG
    print_timespec(t1, "t1");
    print_timespec(t2, "t2");
#endif
    long long nsecs = (t2->tv_sec - t1->tv_sec) * NSECPSEC + t2->tv_nsec -
                      t1->tv_nsec;
    assert(nsecs >= 0);
    d->tv_sec = nsecs / NSECPSEC;
    d->tv_nsec = nsecs % NSECPSEC;
}

/*
 * benchmark_time_get_secs -- get total number of seconds
 */
double
benchmark_time_get_secs(benchmark_time_t *t)
{
    return (double)t->tv_sec + (double)t->tv_nsec / NSECPSEC;
}

/*
 * benchmark_time_get_nsecs -- get total number of nanoseconds
 */
unsigned long long
benchmark_time_get_nsecs(benchmark_time_t *t)
{
    unsigned long long ret = t->tv_nsec;

    ret += t->tv_sec * NSECPSEC;

    return ret;
}

/*
 * benchmark_time_compare -- compare two moments in time
 */
int
benchmark_time_compare(const benchmark_time_t *t1, const benchmark_time_t *t2)
{
    if (t1->tv_sec == t2->tv_sec)
        return (int)((long long)t1->tv_nsec - (long long)t2->tv_nsec);
    else
        return (int)((long long)t1->tv_sec - (long long)t2->tv_sec);
}

/*
 * benchmark_time_set -- set time using number of nanoseconds
 */
void
benchmark_time_set(benchmark_time_t *time, unsigned long long nsecs)
{
    time->tv_sec = nsecs / NSECPSEC;
    time->tv_nsec = nsecs % NSECPSEC;
}

/*
 * number of samples used to calculate average time required to get a current
 * time from the system
 */
#define N_PROBES_GET_TIME 10000000UL

/*
 * benchmark_get_avg_get_time -- calculates average time required to get the
 * current time from the system in nanoseconds
 */
unsigned long long
benchmark_get_avg_get_time(void)
{
    size_t i;
    benchmark_time_t time;
    benchmark_time_t start;
    benchmark_time_t stop;

    benchmark_time_get(&start);
    for (i = 0; i < N_PROBES_GET_TIME; i++) {
        benchmark_time_get(&time);
    }
    benchmark_time_get(&stop);

    benchmark_time_diff(&time, &start, &stop);

    unsigned long long avg =
        benchmark_time_get_nsecs(&time) / N_PROBES_GET_TIME;

    return avg;
}

int main()
{
    unsigned long long Get_time_avg;
    Get_time_avg = benchmark_get_avg_get_time();
    printf("Average time required to get the current time from the system: %llu nanoseconds\n", Get_time_avg);
    return 0;
}