Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!agate!saturn!munnari!latcs1.oz.au!rhys@uunet.UU.NET
From: munnari!latcs1.oz.au!rhys@uunet.UU.NET (Rhys Francis)
Newsgroups: comp.os.research
Subject: Re: Question on thread/process scheduler interaction
Message-ID: <5321@saturn.ucsc.edu>
Date: 30 Oct 88 02:26:12 GMT
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Organization: Comp Sci, La Trobe Uni, Australia
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Approved: comp-os-research@jupiter.ucsc.edu


I am about to do some simulations on solutions to the problem
fouts@lemming (Marty Fouts) describes in article <5296@saturn.ucsc.edu>
but in a more general context and would be interested in proposals and
performance results already known.

The more general problem I am investigating is the notion that the O.S.
of a large shared memory multiprocessor will need to vary the share of
CPU resource allocated to jobs over time. Hence a parallel program must
be implemented in a fashion which allows it to continue to execute effectively
as processors time-out and are re-allocated to other jobs.
This problem has to be addressed if such beasts are going to be used
in general purpose multiprogrammed and time-sharing environments.

It seems that the O.S. schedular needs knowledge of the thread level
scheduling structures which creates security/programming/performance problems
if applications wish to exercise control over thread scheduling.
It also seems that interrupt logic and handling needs to interfere at the
task level as well as at the process level. Finally, if tasks or processes
attempt self scheduling across loops (perhaps using Fetch and Add style hardware
support) time-out interrupts in the body of an iteration can be nasty.

Further questions concern appropriate O.S. job scheduling and CPU scheduling
policies as well as methods for real-time acquisition of accurate measures
of the CPU resource being used by a parallel application.

Dr. Rhys Steven Francis,          ACSnet:  CSnet:    rhys@latcs1.oz
Dept. of Computer Science,        ARPA:    rhys%latcs1.oz@uunet.uu.net
LaTrobe University,               JANET:   latcs1.oz!rhys@ukc
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