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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.arch
Subject: Re: Very large memories
Message-ID: <7112@utzoo.UUCP>
Date: Thu, 11-Sep-86 13:47:34 EDT
Article-I.D.: utzoo.7112
Posted: Thu Sep 11 13:47:34 1986
Date-Received: Thu, 11-Sep-86 13:47:34 EDT
References: <1164@ncr-sd.UUCP>
Organization: U of Toronto Zoology
Lines: 15

> Another case peculiar to Unix systems is VFORK. Why duplicate
> the whole address space when the most likely thing to do next
> is EXEC, which will clobber the space you just copied?

Please, not "to Unix systems" but "to Berklix systems".  The vast majority
of Unix systems do not have vfork.  Even a lot of Unix systems with well-
designed virtual-memory systems lack vfork:  there is no intrinsic reason
why a plain, ordinary fork has to copy the whole address space.  It has to
*look* that way to the program, but with a modicum of cooperation from the
memory-management hardware, that's easy enough.  Even the Berklix manuals
warn you that vfork is a temporary kludge around implementation difficulties,
not a permanent part of the system.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry