Measuring small consecutive memcpy

measure.c

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<time.h>
int main(){
        void *a, *b;
        struct timespec start, end;
        unsigned int i;

        a = malloc(128);
        b = malloc(128);
        memset(a, 127, 128);
        memset(b, 0, 128);

        for(i=0;i<1000;i++){
                clock_gettime(CLOCK_MONOTONIC, &start);
                memcpy(b, a, 32);
                clock_gettime(CLOCK_MONOTONIC, &end);
                {
                        long int nsec = (end.tv_sec - start.tv_sec) * 1000000000 +
                                (end.tv_nsec - start.tv_nsec);
                        printf("%u ns\n", nsec);
                }
        }

        return 0;
}