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 allocate. N