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RE: [Xen-users] maximum domU performance

To: "Bruce Edge" <bruce.edge@xxxxxxxxx>, "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Subject: RE: [Xen-users] maximum domU performance
From: Jeff Sturm <jeff.sturm@xxxxxxxxxx>
Date: Thu, 15 Oct 2009 10:40:11 -0400
Cc: Zu <zuzhihui@xxxxxxxxx>, Xen User-List <Xen-users@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: [Xen-users] maximum domU performance
> -----Original Message-----
> What if the dom0 has no tasks once the domU is up and running?
> eg: disable syslog, cron, etc on dom0
> Can one assign all cores to the domU?
> Or, must one core remain idle dedicated to handling dom0 processing?

Dom0 can share a core, but it'll be timesliced if the dom0 has things to
do.  Which may not be good overall.  I like to pin dom0 to one (or more)
core, and leave everything else to domU.

Whether this helps you or not depends on what the domU is doing.  If
your domU is compute-intensive, it may benefit from having access to all
cores.  But if it routinely does any block or network I/O, the dom0
needs to get involved, since that's where the backend drivers usually
run.  And if dom0 has to wait for a CPU to  become available, that may
delay domU I/O.


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