Path: utzoo!mnetor!uunet!husc6!yale!cmcl2!nrl-cmf!ames!ucsd!sdcsvax!ijh@tut.fi
From: ijh@tut.fi (Ilkka Haikala)
Newsgroups: comp.os.research
Subject: working sets and shared pages
Message-ID: <4780@sdcsvax.UCSD.EDU>
Date: 15 Mar 88 08:39:54 GMT
Sender: nobody@sdcsvax.UCSD.EDU
Lines: 40
Approved: comp-os-research@ucsd.edu

Hello

You requested information about DWS-implementations in environments,
where segments are shared between processes. I know about three or two
such implementations:

1. Nokia Electronics (a Finish company) is manufacturing an Ada
computer called MPS 10. The architecture resembles somewhat the IBM
S/38. It's a "single level storage" computer, and therefore all
memory is (potentially) shared by definition.  Protection and
addressing is based on Capabilities. The replacement algorithm is a
DWS approximation. There is no information published about the system,
but I know the details of the implementation quite well myself (and I
can also pass information to you if you need it).

2. The MUMS project in university of Lund (Sweden) is implementing a
multiprocessor shared memory system, where the replacement policy is
based on an DWS-approximation. The relatively exotic memory
organization of the system makes things even more complicated than in
the case of MPS 10. There are some drafts describing the
implementation under work. For more information, you can contact 
professor Lars Philipson (lars@ikaros.dst.lu.se).

3. The DWS-implementation for Gould superminis has been described in

%A Akhtar, P.,
%T A Replacement for Berkeley Memory Management.
%U Proceedings of the USENIX 1987 Technical Conference and Exhibition,
%U Phoenix, Arizona (June 1987) pp. 69-79.

I don't have the paper at hand now, but as far as I remember, the
system is using DWS -approximation. Probably, the sharing of pages
is solved somehow. (Also, this is a multiprocessor implementation,
which makes things more interesting.)

sincerely: Ilkka Haikala
Technical University of Tampere, Finland

P.S. If you have knowledge about some other systems, I would be most
greatful to get the references.