Newsgroups: comp.arch
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Paging page tables
Message-ID: <1990Jul6.160004.896@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <3300142@m.cs.uiuc.edu> <9758@pt.cs.cmu.edu> <PCG.90Jun30230310@odin.cs.aber.ac.uk> <58001@bbn.BBN.COM> <5796@titcce.cc.titech.ac.jp>
Date: Fri, 6 Jul 90 16:00:04 GMT

In article <5796@titcce.cc.titech.ac.jp> mohta@necom830.cc.titech.ac.jp (Masataka Ohta) writes:
>If a large process want to fork(), it requires a large amount of virtual
>memory space (twice the size of the process). So, if the process almost
>used up virtual memory space, the process can not fork(). Copy-on-write
>won't help.

Nonsense.  There need not be any concept of "using up virtual memory space".
Virtual memory is *virtual*; only when those pages need to become real do
they consume resources.  Forking large processes without needing lots more
memory/disk just requires an intelligent implementation.  Unfortunately,
intelligent implementors are scarce.

Vfork is an abomination invented by lazy people; the sooner it goes,
the better.  (Please don't tell me that hardware problems prevented them
from implementing copy-on-write; copy-on-access they *could* have done,
and it would have been almost as good.)
-- 
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."  -John K. Ousterhout |  henry@zoo.toronto.edu   utzoo!henry
