Path: utzoo!utgpu!watserv1!watmath!att!pacbell!pacbell.com!ucsd!swrinde!cs.utexas.edu!mailrus!bbn.com!lkaplan
From: lkaplan@bbn.com (Larry Kaplan)
Newsgroups: comp.arch
Subject: Re: fork() vs vfork() and COW
Message-ID: <58086@bbn.BBN.COM>
Date: 10 Jul 90 14:41:52 GMT
References: <1122@sirius.ucs.adelaide.edu.au> <3830012@hpcupt1.HP.COM> <58053@bbn.BBN.COM> <476@exodus.Eng.Sun.COM>
Sender: news@bbn.com
Reply-To: lkaplan@BBN.COM (Larry Kaplan)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 34

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):
>
>	(code was presented here)
>
>% time ./a.out (fork)
>0.2u 4.3s 0:09 47% 0+140k 0+0io 0pf+0w
>% time ./a.out x  (vfork)
>0.0u 4.1s 0:04 92% 0+140k 0+0io 0pf+0w
>
>fork() seems to take twice as long as vfork() for a small process.
>
>Of course if exec() is sufficiently slow you're right, this will not be
>significant.
>
>--
>David DiGiacomo, Sun Microsystems, Mt. View, CA  david@eng.sun.com

I have some trouble with these numbers.  The system times are virtually
identical.  In addition, calling exit() after a vfork() is not usually a
good idea.  Also, since the argument is fork-exec vs. vfork-exec, this
timing is fairly inappropriate anyway.  The proper thing would be a time
call of some form before the (v)fork() call and one in the program being
exec'd.

Does SunOS 4.1 really have COW?  Where is it documented?  This would be nice
to see.

#include <std_disclaimer>
_______________________________________________________________________________
				 ____ \ / ____
Laurence S. Kaplan		|    \ 0 /    |		BBN Advanced Computers
lkaplan@bbn.com			 \____|||____/		10 Fawcett St.
(617) 873-2431			  /__/ | \__\		Cambridge, MA  02238