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From: dik@cwi.nl (Dik T. Winter)
Newsgroups: comp.unix.cray
Subject: Re: Summary for Protection in Cray
Message-ID: <2825@charon.cwi.nl>
Date: 18 Jan 91 14:59:38 GMT
References: <1991Jan10.230715.404@agate.berkeley.edu> <1892@sun13.scri.fsu.edu> <DREIER.91Jan13223533@husc9.harvard.edu>
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In article <DREIER.91Jan13223533@husc9.harvard.edu> dreier@husc9.harvard.edu (Roland Dreier) writes:
 > I guess one thing that should be noted about how Crays handle memory: under
 > Unicos, since it lacks virtual memory, whole jobs get swapped.  What this
 > means is that if I'm running two jobs on a 256 megaword machine and each of
 > them wants 129 megawords of memory, every time a job gets swapped out, I
 > have to do 129 megawords of IO, rather than just the small amount of overlap
 > that I "really" have to do; so clearly, even a slightly slower virtual memory
 > system would be at an advantage here.
 > 
But this is not a defect of the lack of VM; it is a defect of the OS.
If the OS wants to swap out the complete job it can do so, but it is
not necessary.
--
dik t. winter, cwi, amsterdam, nederland
dik@cwi.nl