Trying to demonstrate that I have a CPU cache

cache.c

/**
 * The way this works:
 * ./cache array_size n_repeats allocates an array of size 32 *
 * array_size, and * adds up all the numbers in it n_repeats times.
 *
 * Try for example
 * $ time ./cache 1 3200000
 * $ time ./cache 3200000 1
 *
 * This was supposed to demonstrate that I have a CPU cache, but it does
 * not =(
 */
#include <stdio.h>
#include <stdlib.h>

#define BLOCK_SIZE 32

int main(int argc, char** argv) {
    if (argc < 3) {
        printf("Usage: ./cache array_size num_repeats\n");
        exit(0);
    }
    int array_size = atoi(argv[1]) * BLOCK_SIZE;
    int n_repeats = atoi(argv[2]);
    char* chars = malloc(sizeof(char) * array_size);
    // Initialize our array
    int i,k;
    int total = 0;
    for (k = 0; k < n_repeats; k++) {
        for (i = 0; i < array_size; i++) {
          chars[i] = rand();
        }
        for (i = 0; i < array_size; i++) {
          total += chars[i];
        }
    }
}