Simplistic way of measuring memcpy() performance on Unix systems.

memcpy-speed.c

#include <sys/time.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

int main() {
    struct timeval t0, t1;
    unsigned int i;
    unsigned int mb_size = 64;
    unsigned int rep = 200;

    for (unsigned int mb_size = 64; mb_size <= 1024; mb_size *= 2) {
        size_t size = mb_size * 1024 * 1024;

        void *src = malloc(size);
        void *dst = malloc(size);

        gettimeofday(&t0, NULL);

        for (int i = 0; i < rep; i++) {
            memcpy(src, dst, size);
        }

        gettimeofday(&t1, NULL);

        free(src);
        free(dst);

        printf("Copied %d MB in %.2g seconds\n", mb_size, (t1.tv_sec - t0.tv_sec + 1E-6 * (t1.tv_usec - t0.tv_usec)) / rep);
    }
}