/* gcc -W -Wall -o hog hog.c */

#include <stdlib.h>
#include <stdio.h>

#include <sys/time.h>
#include <unistd.h>

int main(void)
{
	int pages, pagesize, i;
	unsigned char *mem;
	struct timeval tv;
	
	pages = sysconf(_SC_PHYS_PAGES);
	if (pages < 0) {
		perror("_SC_PHYS_PAGES");
		return EXIT_FAILURE;
	}
	pages = (3 * pages) / 4;

	pagesize = sysconf(_SC_PAGESIZE);
	if (pagesize < 0) {
		perror("_SC_PAGESIZE");
		return EXIT_FAILURE;
	}

	mem = malloc(pages * pagesize);
	if (!mem) {
		fprintf(stderr, "out of memory\n");
		return EXIT_FAILURE;
	}
	for (i = 0; i < pages; i++)
		mem[i * pagesize] = 0;

	gettimeofday(&tv, NULL);
	srand((unsigned int)tv.tv_sec);

	while (1) {
		struct timeval start;

		getchar();

		gettimeofday(&start, NULL);
		for (i = 0; i < 2 * pages; i++)
			mem[(rand() / (RAND_MAX / pages + 1)) * pagesize] = 0;
		gettimeofday(&tv, NULL);

		timersub(&tv, &start, &tv);
		printf("%lu.%lu\n", tv.tv_sec, tv.tv_usec);
	}

	return EXIT_SUCCESS;
}