memory_test/demo.c

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


#define MB_BYTES (1024*1024)

int main(int argc, char **argv)
{
	unsigned long *p;
	unsigned long *m;
	int i = 0;
	int max;

	const char *file_path = argv[1];
	int fd = open(file_path, O_RDONLY);
	if (fd == -1) {
		perror("open");
		return 1;
	}

	struct stat sb;
	if (fstat(fd, &sb) == -1) {
		perror("fstat");
		close(fd);
		return 1;
	}

	size_t file_size = sb.st_size;

	printf("%ld, %d Kb\n", file_size, file_size/1024);
	void *mapped = mmap(NULL, file_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
	if (mapped == MAP_FAILED) {
		perror("mmap");
		close(fd);
		return 1;
	}
	m = mapped;

	max = file_size / 8;
	p = malloc(file_size);

	for (i = 0; i < max; i++) {
		*(p + i) = *(m + i);
		*(m + i) = *(p + i);
	}
	
	fork();
	fork();
	fork();

	while(1);

	return 0;
}