> IMHO, If the OS/hypervisor can detect the cpu cores, you should
> definitely be able to assign.
> Stephen Neoh wrote:
> > In that case, as i know, each physical core has it's own id. Can i
> > assign a specific core id to a domU/domO?
Actually you can assign individual logical processors (i.e. hyperthreads, if
you have them) to domains. By assigning all the logical processors on a
core, you can assign a core to the domain; by assigning all the logical
processors in a package you can assign all the cores in that package, and so
Of course, the domain isn't actually getting direct access to the processors -
it still gets scheduled by Xen. But if you arrange in the domain config
files (and in xend-config.sxp for dom0) that each is assigned to run only on
one specific logical CPU then it's basically equivalent to a domain running
on each logical CPU all the time - because Xen won't have anything else to
It can be a performance win to assign a dedicated hyperthread (or potentially
a core, but this would depend on your workload) to dom0. I've had the
impression that dom0 doesn't really need to be SMP anyhow to ensure decent
performance to the domUs. Assigning at least a hyperthread to dom0 can
improve IO performance, although if you assign a core to dom0 obviously other
domains can't use it for processing anymore.
For other domains, you may still find it's more flexible to let Xen schedule
them across the available processors. You can still cap the amount of CPU a
domain uses. But yes, you can pin domains to CPUs to get the effect of each
core running a different domain.
Hope this helps,
> > On Nov 28, 2007 6:03 PM, Sadique Puthen < sputhenp@xxxxxxxxxx
> > <mailto:sputhenp@xxxxxxxxxx>> wrote:
> > Stephen Neoh wrote:
> > > I'm quite new to XEN here. I got a question to ask about the XEN
> > > configuration. Is it possible to disable the SMP function on the
> > dom0
> > > and assign each single domU to have direct access on the multicore
> > > processor like Intel Quadcore?
> > Yes, Edit /etc/xend/xend-config.sxp and use (dom0-cpus x) to assign a
> > single cpu to dom0.
> > For domus, define vcpus = x and cpus = x in guest configuration
> > file to
> > assign a single core or cpu to a guest. See /etc/xen/xmexample1
> > for more
> > details.
> > --Sadique
> > ------------------------------------------------------------------------
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> > <http://lists.xensource.com/xen-users>
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!
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