Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!reading!cf-cm!csisles!beaumont
From: beaumont@CompSci.Bristol.AC.UK (Tony Beaumont)
Newsgroups: comp.sys.sequent
Subject: timing parallel programs
Keywords: timing, sequent, multi-processor
Message-ID: <1324@csisles.Bristol.AC.UK>
Date: 8 Feb 90 09:19:45 GMT
Organization: Dept of Computer Science, University of Bristol, UK.
Lines: 34

We have a prototype OR-parallel Prolog system, written in C and running on a
sequent symmetry with 12 processors and a micro-second clock.

We want to get accurate timings of the run-times of Prolog programs when we
use 1, 2, ... 11 processors in order to accurately measure the speed-ups.

Our sequent is also running X-windows and there are 4 or 5 X-terminals
attached.

THE PROBLEM...
1.  How can we be sure that a program using (say) 6 DYNIX processes will
be run on 6 processors without interruption by other processes (ie
operating system processes, X-windows processes etc)

Is there a way to get a processor to exclusively run a process?

2.  Our current solution is to ask other users to log off when we make
timing runs, ensuring the load on the machine is as low as possible.
However, operating system processes are still running and although we
always leave at least 1 processor idle, how can we be sure that the
operating system processes do not interfere with (slow down) the processes
we are timing?  Also this approach is rather unfortunate in that we
require all other users to log off which in effect means that we have to
make our timings during the night.

email replies directly to me and if there is any interest I'll post a
summary of responses.

-Tony Beaumont
email (JANET): beaumont@uk.ac.bristol.compsci
Post: Department of Computer Science
      University of Bristol
      Bristol BS8 1TR
      UK