/* rtorrent + FreeBSD pagedaemon prombel simulator
 * 2014 Rozhuk Ivan <rozhuk.im@gmail.com>
 *
 * compile-command: "clang -Wall -O2 -o testvm testvm.c"
 */


#include <sys/cdefs.h>
#include <sys/types.h>
#include <sys/stat.h> // chmod, fchmod, umask
#include <sys/uio.h> /* readv, preadv, writev, pwritev */
#include <sys/mman.h> /* mmap, munmap */

#include <errno.h>
#include <fcntl.h> /* open, fcntl */
#include <stdio.h>  /* snprintf, fprintf */
#include <string.h> /* bcopy, bzero, memcpy, memmove, memset, strnlen, strerror... */
#include <unistd.h> /* close, write, sysconf */
#include <stdlib.h> /* malloc, exit */

#define LOG_ERR(error, descr)							\
	fprintf(stdout, "fn: %s, line: %i, error: %i - %s, %s\n",		\
		__FUNCTION__, __LINE__, error, strerror(error), descr);

int
main(int argc, char *argv[]) {
	int error = 0, fd;
	const char *file_name = (const char *)"/testvn.tmp";
	off_t mb = (1024 * 1024); /* 1 megabyte. */
	off_t file_size = (4 * 1024 * mb); /* Set to x2 RAM size. */
	off_t write_size = (32 * mb); /* Write block size. */
	off_t i, j, page_size;
	uint8_t *mem;

	fd = open(file_name, (O_RDWR | O_CREAT/* | O_DIRECT*/), 0600);
	if (-1 == fd) {
		error = errno;
		LOG_ERR(error, "open()");
		goto err_out;
	}
	if (0 != flock(fd, LOCK_EX)) {
		error = errno;
		LOG_ERR(error, "flock()");
		goto err_out;
	}
	if (0 != ftruncate(fd, file_size)) {
		error = errno;
		LOG_ERR(error, "ftruncate()");
		goto err_out;
	}

	page_size = sysconf(_SC_PAGE_SIZE);
	for (i = 0; i < (file_size / write_size); i ++) {
		mem = mmap(NULL, write_size, (PROT_READ | PROT_WRITE),
		    (MAP_SHARED | MAP_NOCORE), fd, (i * write_size));
		if (MAP_FAILED == mem) {
			error = errno;
			LOG_ERR(error, "mmap()");
			goto err_out;
		}
		for (j = 0; j < (write_size / page_size); j ++) {
			mem[(j * page_size)] = 1;
		}
		//msync(mem, file_size, MS_SYNC);
		//posix_madvise(mem, file_size, MADV_FREE);
		munmap(mem, file_size);
	}

err_out:
	close(fd);
	//unlink(file_name); /* Delete file to free all mem. */

	return (error);
}