[CentOS-virt] What are KVM guest cores?

Nick oinksocket at letterboxes.org
Fri Nov 19 05:25:26 EST 2010

On 18/11/10 23:32, MargoAndTodd wrote:
> Do you have a rule of thumb as to how many core to assign
> to a guest?  For instance, with an Intel x5650 with 6 real
> and 12 hyperthreaded cores, how many cores would you assign
> to the guest?

You may already know this, but don't rely on hyperthreading giving you very much
extra.  At best it's squeezing some useful work out of what would be a few idle
cycles waiting for the instruction pipeline to re-fill.  At worst it degrades
performance and has been known to be a security hazard.

Therefore, in your given case, think six not twelve.  Common advice is to leave
one core for the host OS/scheduler.  Which leaves you with 5 physical CPUs to


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