Makefile

test: test.c Makefile
	gcc -O3 -Wall -Werror -std=c99 -o test test.c

test.c

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

int main()
{
   const int SIZE = 256 * 1024 * 1024;
   int *x;
   struct timeval ts, te, t;

   x = malloc(SIZE * sizeof(int));

   gettimeofday(&ts, NULL);
   for (int i = 0; i < SIZE; i++) {
      x[i] = i;
   }
   gettimeofday(&te, NULL);
   timersub(&te, &ts, &t);
   printf("write = %d.%06d\n", (int) t.tv_sec, (int) t.tv_usec);

   long m = 0;
   for (int j = 0; j < 100000; j++) {
      gettimeofday(&ts, NULL);
      long n = 0;
      for (int i = 0; i < SIZE; i++) {
         n += x[i];
      }
      gettimeofday(&te, NULL);
      timersub(&te, &ts, &t);
      float secs = (t.tv_sec + (t.tv_usec / 1000000.0));
      printf(" read = %d.%06d (%.1f MB/s)\n",
         (int) t.tv_sec, (int) t.tv_usec,
         ((SIZE * sizeof(int)) / secs) / (1024 * 1024));

      m += n;
   }
   printf("%ld\n", m);
   
   return 0;
}