Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pasteur!agate!saturn!darrell@midgard.ucsc.edu
From: darrell@midgard.ucsc.edu (Darrell Long)
Newsgroups: comp.os.research
Subject: Re: Question for the week -- distributed Multics?
Message-ID: <6175@saturn.ucsc.edu>
Date: 30 Jan 89 21:30:22 GMT
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Approved: comp-os-research@jupiter.ucsc.edu


Here is a summary of the responses to my "question for the week."  Thanks to
everyone who responded.

DL

In article <6154@saturn.ucsc.edu> you write:
>I'd like to get some opinions on this: How much sense does a distributed
>version of Multics make?

%A W. A. Montgomery
%T Measurements of Sharing in Multics
%J PROC 6th SOSP (in Operating Systems Review)
%V 11
%N 5
%D NOV 1977
%P 85-90
%X little empirical use (by users) of Multics segment sharing
%X subset of sharing probably better for distributed systems

Would it be better to ask:
	what subset of Multics makes sense for distributed systems?

--
Paul M. Aoki, aoki@postgres.Berkeley.EDU



In article <6154@saturn.ucsc.edu> darrell@midgard.ucsc.edu (DL) writes:
>[Memory-mapped file system with shared segments across machines]

See several papers by Kai Li.  Only one I have handy:

Kai Li
Paul Hudak
Memory Coherence in Shared Virtual Memory Systems.
Proceedings 1986 ACM Conference on Principles of Distributed Systems
pp. 229-239

-- 
Pardo, pardo@cs.washington.edu



In article <6154@saturn.ucsc.edu> you write:
#
#I'd like to get some opinions on this: How much sense does a distributed
#version of Multics make?  That is, a memory mapped file system with shared
#segments across machines?

As an abstract concept, it makes sense.  It would probably be *HELL* to
implement, though.  Many of Multics' ideas still make sense; memory-
mapped files does.  The biggest problem is sharing the actual files; in
Multics, all processes that mapped in a segment used the same physical
memory.  In a distributed system, that would be a very bad idea, since
the physical memory would likely be on another node and thus be very
costly to access.  So, we could have a Multics-type OS on each machine,
and have files available to all, but that isn't what you were looking
for, is it?

replies welcomed

ethan
-- 
ethan miller, bandersnatch@ernie.berkeley.edu   


In article <6154@saturn.ucsc.edu> darrell@midgard.ucsc.edu (DL) writes:

>I'd like to get some opinions on this: How much sense does a distributed
>version of Multics make?  That is, a memory mapped file system with shared
>segments across machines?

I hope it makes a lot of sense;  I am proposing just such a scheme for my 
doctoral research.  Specifically, a virtual storage memory management 
scheme that is very much like that of Multics (and therefore NOS/VS as 
well), but with extension to support segments located anywhere in the 
network.  When a reference to a non-local segment is made, a special
lightweight transport protocol fetches a copy across the network for local
access.

If you're interested in more details, send me e-mail.

-- 
James Sterbenz, jps@wucs1.wustl.edu