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Re: [Xen-devel] compute performace problem

To: Steven Hand <Steven.Hand@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] compute performace problem
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sat, 23 Apr 2005 16:14:39 +0100
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On 23 Apr 2005, at 16:06, Steven Hand wrote:

One of my users discovered large deviations in execution time for his
mpi jobs on xenUs.  I can reproduce the problem running his job on
a single VM.  On a native linux box the job completes in 64 secs +/-
a second or so.  On a xenU, it completes somewhere between 64 and 250
secs. This is true on 2.0.5 (2.6.10-xenU) and 2.0-testing(2.6.11-xenU).
I tried xen-unstable but it seemed any task was taking 4 times as
long as on 2.0 so I guess its still too unstable.

Any suggestions I can try?

Can you repeat the experiment using the round robin scheduler in Xen (i.e.
boot with xen option "sched=rrobin")?

Probably will be worse -- I'm not certain that the rrobin scheduler is even smart enough not to include the idle domain in its round-robin schedule. An important reason why I killed it in the unstable tree.

 -- Keir


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