[CentOS-virt] What are KVM guest cores?

[MargoAndTodd]

On 11/18/2010 04:01 PM, Kenni Lund 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?
>
> It fully depends on the load of your guests and how many guests you
> want/need to run on a single server.
>
> You need to perform some testing to know what will work the best in
> your case. One thing to remember though: In your case, if you create
> two guests with 12 virtual CPUs each, and one of them crashes and take
> all its 12 virtual CPUs up to 100%, it will essentially take most of
> the processing power away from the second guest, leaving the second
> guest in a close-to-useless state (depending on your scheduler, but
> you get the point). If you on the other hand had assigned 6 cores to
> each of them, the second guest would have remained unaffected, since
> it just uses the 6 cores with no load. So if your guest will not
> utilize the extra CPUs anyway, then don't assign them.
>
> Best regards
> Kenni

Thank you!
-T