#include <sys/mman.h>

#define SIZE (4096*1024 * 256)
#define PAGE_SIZE 4096

main()
{

	char *addr;
	int i;

	addr = mmap(0, SIZE, PROT_WRITE|PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
	if (addr == MAP_FAILED) {
		perror("Can't mmap");
		exit(1);
	}

	if (madvise(addr, SIZE, MADV_MERGEABLE)) {
		perror("Can't madvise");
		exit(1);
	}

	for (i = 1; i < SIZE/PAGE_SIZE; i += 2)
		munmap(addr + i * PAGE_SIZE, PAGE_SIZE);

	while (1) {
		for (i = 0; i < SIZE/PAGE_SIZE; i += 2) {
			*(addr + i * PAGE_SIZE) = (char)0;
		}
		sleep(10);
	}
}