#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/time.h>

#define SIZE 500*1024*1024
#define PAGE_SIZE 4096          // 4KB
#define CHUNK_SIZE 8 * 1024     // 8KB

unsigned long long tv_to_ms(struct timeval tv)
{
	return tv.tv_sec * 1000 + tv.tv_usec / 1000;
}

int main()
{
	int i;
	char *c;
	pid_t pid;
	unsigned long *p;
	struct timeval tv_b, tv_e;;

	p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
	if (!p) {
		perror("fail to get memory");
		exit(-1);
	}

	c = (unsigned char *)p;

	/* fill data */
	for (i = 0; i < SIZE / 8; i += 8)
		*(p + i) = 0xffff + i;

	/* trigger pageout and get time of pageout */
	gettimeofday(&tv_b, NULL);
	madvise(p, SIZE, MADV_PAGEOUT);
	gettimeofday(&tv_e, NULL);

	printf("swp out bandwidth: %ld bytes/ms\n", SIZE/(tv_to_ms(tv_e) - tv_to_ms(tv_b)));

	/* read to trigger swapin and */
	gettimeofday(&tv_b, NULL);
	for (i = 0; i < SIZE; i += PAGE_SIZE)
		*(c + i) = i;
	gettimeofday(&tv_e, NULL);

	printf("swp in  bandwidth: %ld bytes/ms\n", SIZE/(tv_to_ms(tv_e) - tv_to_ms(tv_b)));

	pid = fork();

	if (pid) {
		munmap(p, SIZE);
		sleep(3);
		return 0;
	}

	madvise(p, SIZE, MADV_PAGEOUT);

	while (1) {
		sleep(10);
	}

	return 0;
}