http://pomozok.wordpress.com/2011/11/29/cpu-cache-thrashing/

gistfile1.c

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

// my CPU has 32K of L1 cache
#define L1_CACHE_CAPACITY (32768 / sizeof(int))

int array[L1_CACHE_CAPACITY][L1_CACHE_CAPACITY];

struct timespec time_diff(struct timespec start, struct timespec end) {
  struct timespec temp;

  if (end.tv_nsec - start.tv_nsec < 0) {
    temp.tv_sec = end.tv_sec - start.tv_sec - 1;
    temp.tv_nsec = 1000000000 + end.tv_nsec - start.tv_nsec;
  } else {
    temp.tv_sec = end.tv_sec - start.tv_sec;
    temp.tv_nsec = end.tv_nsec - start.tv_nsec;
  }

  return temp;
}

int main(void) {
  struct timespec start, end;
  int i, j;

  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);

  for (i=0; i<L1_CACHE_CAPACITY; i++)
    for (j=0; j<L1_CACHE_CAPACITY; j++)
      array[i][j] = i*j;

  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);


  struct timespec delta = time_diff(start, end);
  printf("Delta is %ld:%6ld\n", delta.tv_sec, delta.tv_nsec);

  return EXIT_SUCCESS;
}