Newsgroups: comp.parallel.pvm
From: Thomas Manke <tm10010>
Subject: Priorities,CPU-times and PVM
Organization: DAMTP, University of Cambridge, UK.
Date: 21 Aug 1995 13:16:06 GMT
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Message-ID: <41a0um$rh4@lyra.csx.cam.ac.uk>

I run PVM on 4 DEC-ALPHAS with 75 Mbyte spread across initially (2 min CPU).
Later in the program I only transfer minor amounts of data with PVM -
say a few bytes each minute CPU.

Having niced all processes I usually get quite high priorities on those
machines. However, I hardly get CPU-times above 10% . This is apparently
due to message passing because the serial version of my programs would
(effectively) run much faster - i.e. above 90% CPU-time with me being the only
user.

If I were to add different architectures (as I've used SUNs and HPs in the
past) this problem gets worse - apparently due to data conversion done by PVM.

In fact, sometimes I wouldn't get any CPU-time at all.
Has this to do with the way PVM works ?

I wonder if someone has similar problems - or even a solution ?


Thanks
Thomas.


