/*
 * Copyright (C) Ingo Molnar, 2004
 *
 * Create 80 MB worth of finegrained mappings to a shmfs file.
 */
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>

/* 80 MB of mappings */
#define CACHE_PAGES 20000

#define PAGE_SIZE	4096
#define CACHE_SIZE	(CACHE_PAGES*PAGE_SIZE)
#define WINDOW_PAGES	(CACHE_PAGES*9/10)
#define WINDOW_SIZE	(WINDOW_PAGES*PAGE_SIZE)
#define WINDOW_START	0x48000000

int main(void)
{
	char *data, *ptr, filename[100];
	char empty_page [PAGE_SIZE];
	int i, fd;

	sprintf(filename, "/dev/shm/cache%d", getpid());
	fd = open(filename, O_RDWR|O_CREAT|O_TRUNC,S_IRWXU);
	unlink(filename);

	for (i = 0; i < CACHE_PAGES; i++)
		write(fd, empty_page, PAGE_SIZE);
	data = mmap(0, WINDOW_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED , fd, 0);

	for (i = 0; i < WINDOW_PAGES; i++) {
		ptr = (char*) mmap(data + i*PAGE_SIZE, PAGE_SIZE,
				PROT_READ|PROT_WRITE, MAP_SHARED | MAP_FIXED,
					fd, (WINDOW_PAGES-i)*PAGE_SIZE);
		(*ptr)++;
	}
	printf("%d pages mapped - sleeping until Ctrl-C.\n", WINDOW_PAGES);
	pause();

	return 0;
}