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From: Rick.Rashid@cs.cmu.edu
Newsgroups: comp.os.mach
Subject: Re: message passing & migration
Message-ID: <AbtWpxK00jdXQBZlFC@cs.cmu.edu>
Date: 19 Mar 91 15:25:49 GMT
Organization: Carnegie Mellon, Pittsburgh, PA
Lines: 22

Let me add a bit to Michael's note:

Ed Zayas in the mid-80's did a PhD thesis in which (among other things)
he implemented and use network copy-on-reference in the Accent OS
(the predecessor to Mach).  His work included studying network copy
on reference for normal message passing and for process migration.

Basically, his results were encouraging, but it was felt within the
group that the problems associated with using network copy on reference
in the face of network and node failures were too great to justify
this as a standard feature.

Ed work did lead indirectly, though, to the subsequent development of
a workable interface for external pagers.  The role of network
copy-on-reference in Accent has essentially been replaced by the
ability in Mach for any task to create a memory object for which it
is the backing store.  This allows data to be explicitly (as opposed
to implicitly) sent by reference in messages.  The effect is the
same, but it is a conscious decision of the implementor rather than
something done by accident.  Generic network shared memory is
provided by the network shared memory server.
-Rick