Article View: comp.arch
Article #22443Re: Multics & Memory mapped files
From: Peter Desnoyers
Date: Tue, 13 Feb 1990 18:04
Date: Tue, 13 Feb 1990 18:04
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If I remember correctly from my computer architecture class several years
back, there is a substantial penalty in kernel complexity to implement a
paging scheme which can page from arbitrary files instead of a
pre-allocated contiguous chunk of disk. (The comparison was between
Multics and some other system of the same vintage - the Multics code was
about 10X longer.) You also end up with a much larger body of code that
must be protected from paging.
It is quite possible to design a VM system that will not allow
memory-mapped file access. The problem is that this system may end up
being faster, simpler, and more robust than one which is able to map user
files into its memory space.
Peter Desnoyers
Apple ATG
desnoyer@apple.com
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!tut.cis.ohio-state.edu!zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!apple!apple.com!desnoyer From: desnoyer@apple.com (Peter Desnoyers) Newsgroups: comp.arch Subject: Re: Multics & Memory mapped files Message-ID: <6662@internal.Apple.COM> Date: 13 Feb 90 18:04:43 GMT Sender: usenet@Apple.COM Organization: Apple Computer, Inc. Lines: 17 References: <5180@crdgw1.crd.ge.com> <12780026@acf4.NYU.EDU>