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From: mohta@necom830.cc.titech.ac.jp (Masataka Ohta)
Newsgroups: comp.arch
Subject: Re: fork() vs vfork() and COW
Message-ID: <5829@titcce.cc.titech.ac.jp>
Date: 11 Jul 90 03:14:02 GMT
References: <1122@sirius.ucs.adelaide.edu.au> <3830012@hpcupt1.HP.COM> <58053@bbn.BBN.COM> <476@exodus.Eng.Sun.COM>
Sender: news@cc.titech.ac.jp
Organization: Tokyo Institute of Technology
Lines: 36

In article <476@exodus.Eng.Sun.COM>
	david@eng.sun.com (Big Ed's Gas Farm) writes:

>I timed a simple test program on a Sun 4/60 running SunOS 4.1 (has COW):

>fork() seems to take twice as long as vfork() for a small process.

But, you should have measured fork() time of a large process.

>#include <signal.h>
>#include <vfork.h>
!
!#define SIZE	(100*1024*1024)
!char mem[SIZE];
>
>main(argc)
>	int argc;
>{
>	int i, pid;
>
>	signal(SIGCHLD, SIG_IGN);
!
!	for(i=0;i<SIZE;i+=1024)	/* to make pages dirty */
!		mem[i]=1;
>
>	for (i = 0; i < 10000; i++) {
>		pid = argc > 1 ? vfork() : fork();
>		if (pid == 0)
!			_exit(0);
!		else
!			wait(0); /* unless you want to spwan 10000 processes
!				    at the same time */
>	}
>}

					Masataka Ohta