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Re: [Xen-users] One or two vcpu?


Am 26.03.2010 um 13:35 Uhr schrieb Peter Privat <peter.privat@xxxxxxxxxxxx>:
> On Fri, 2010-03-26 at 12:24 +0000, Rob MacGregor wrote:
> > > Does it make any difference to the performance for the domU when vcpu
> > > is increased to use 2 cpu:s?
> > That rather depends on what you're doing with that domU.
> Sure! But I wondered if they had any real effect or were just there for
> satisfying software or OS:es that may require more than 1 core or
> whatever. Will the adding of one more virtual CPU (vcpu) have the same
> performance effect as like adding one more physical core to a physical
> hardware? (upgrading a real MB with 1 core cpu to a 2 core cpu).

it depends if you have real cpus! Say, you have 4 cores on your hardware, 
giving 4 vcpus to your domU will result in maximum performance for this domU 
on this hardware. But if you assign more than 4, performance may decrease. If 
you assign only 1 vcpu to your domU, this domU will only use one cpu at a 

I assume the software in your domU will scale over all available cpus.

Hope this helps,



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