Newsgroups: comp.parallel.pvm
From: Richard Moss <rjm@seymour.chem.ubc.ca>
Subject: Q's about xpvm
Organization: The University of British Columbia
Date: Fri, 24 Nov 1995 15:50:55 -0800
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Message-ID: <30B65A5F.41C6@seymour.chem.ubc.ca>

Hi,

I've got a few questions about some things in xpvm that I'm a bit
confused about.  (Great program btw! ...err, at least I think so
if I can figure out how to analyse what its telling me properly ;-)

The first thing is how do you use it to tell whether a group of 
tasks being held up by one of them running slower or whether it
is message passing delays holding things up.  If I have, say, 3
tasks running on 3 separate (real) machines, if one machine is
running slower I expect it to hold things up.  But if they are
all running at the same speed, so the 3 tasks are trying to 
synchronise at the same time, I'd expect some sought of network
holdup.
(ie if you're a task waiting for a message, how do you tell 
whether the wait is due to the task sending the message running
slower, or a wait caused by a network slowdown and so causing the
message to be held up?)

The other confusing thing is what the hosts window is saying.
Is "volume" of network traffic some sort of messages/sec type
thing?  and is, then, the bandwidth a normal bytes/sec type
of thing?
And what is the relationship between colour and volume ...ie
what colour is low volume and what is high? (I figured black
is 0 ;}, but is green more than pink?).  Also how come I get
negative values for bandwidth when I click on a net link?

Thanks,

Richard

