#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/types.h>

#define NR_TASKS	450UL
#define MMAP_SIZE	(256UL << 30)

#define PMD_SIZE	(1UL << 21)
#define NR_PMDS		(MMAP_SIZE / PMD_SIZE)
#define NR_LOOPS	(NR_PMDS * 200)

int main(void)
{
	unsigned long i;
	void *start;
	pid_t pid;

	start = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE,
		     MAP_ANONYMOUS | MAP_SHARED | MAP_NORESERVE, -1, 0);
	if (start == MAP_FAILED) {
		perror("mmap");
		return -1;
	}

	if (madvise(start, MMAP_SIZE, MADV_NOHUGEPAGE)) {
		perror("madvise");
		return -1;
	}

	for (i = 0; i < NR_TASKS; i++) {
		pid = fork();
		if (pid < 0) {
			perror("fork");
			return -1;
		}

		if (!pid)
			break;
	}

	pid = getpid();
	srand48(pid);

	for (i = 0; i < NR_LOOPS; i++) {
		unsigned long offset = (lrand48() % NR_PMDS) * PMD_SIZE;
		unsigned long *addr = start + offset;

		*addr = i;
	}

	return 0;
}