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

int pagesize = 4096;
int instance = 1;
int thread = 1;
int blocksize = 1024*1024; // 1M
int blocks = 1024;	// total 1 G
char *filename="myram";
char *memblock[1024*256];

int memmap(char *argv[], int ppid)
{
	int i,j,fd,err=0,pid,k;
	char file[256];
	sprintf(argv[0],"a%d",ppid);
	sprintf(file,"%s.%d",filename,ppid);
	fd = open(file,O_CREAT|O_TRUNC|O_RDWR,00644);
	if (fd<0) {
		perror("open");
		err = fd;
		goto exit;
	}
	err = unlink(file);
	if (err<0) {
		perror("unlink");
		goto exit_close;
	}
	err = ftruncate(fd,blocksize*blocks);
	if (err<0) {
		perror("ftruncate");
		goto exit_close;
	}
	/* fork more process(thread) to use same share mem file */
	for (i=1;i<thread;i++) {
		pid = fork();
		if (pid <0) {
			perror("fork");
			exit(1);
		}
		if(pid) {
			printf("%d fork  child %d\n",ppid,pid);
		}else {
			sprintf(argv[0],"a%d.%d",ppid,i);
			break;
		}
	}
	for (i=0;i<blocks;i++) {
		void * ptr;
		ptr = mmap(NULL,blocksize, PROT_READ|PROT_WRITE,
			MAP_SHARED, fd, i*blocksize);
		if (ptr==MAP_FAILED) {
			perror("mmap");
			break;
		}
		memblock[i] = ptr;
	}
	/* touch all the share memory like a guest vm */
	while (1) {
		sleep(1);
		for (i=0;i<blocks;i++)
			for (j=0;j<blocksize;j+=pagesize)
				memblock[i][j]=i&0xff;
	}
	err = 0;
exit_close:
	close(fd);
exit:
	return err;
}


int main (int argc, char *argv[])
{
	int i,pid;
	int c;
	while (1) {
		c = getopt(argc,argv,"b:c:i:t:");
		if (c<=0) break;
		switch (c) {
			case 'i':
				/* number of virtual machine */
				instance = strtol(optarg,NULL,0);
				break;
			case 't':
				/* number of process per virtual machine */
				thread = strtol(optarg,NULL,0);
				break;
			case 'c':
				/* number of memory blocks in each virtual machine */
				blocks = strtol(optarg,NULL,0);
				break;
			case 'b':
				/* size of a memory block */
				blocksize = strtol(optarg,NULL,0);
				break;
		}
	}
	printf("i:%d t:%d b:%d c:%d\n",instance,thread,blocksize,blocks);
	for (i=0;i<instance;i++) {
		pid = fork();
		if (pid <0) {
			perror("mainfork");
			exit(1);
		}
		if(pid) {
			printf("mainfork  child %d\n",pid);
		}else {
			return memmap(argv,i);
		}
	}
	return 0;
}