[libvirt-users] Amount CPU's

[Martin Kletzander]

On Wed, Feb 17, 2016 at 07:14:33PM +0000, Dominique Ramaekers wrote:
>Quick question.
>
>In my host, I've got two processors with each 6 cores and each core has
>two threads.
>
>I use iometer to do some testings on hard drive performance.
>
>I get the idea that using more cores give me better results in
>iometer. (if it will improve the speed of my guest is an other
>question...)
>
>For a Windows 2012 R2 server guest, can I just give the guest 24 cores?
>Just to make shure the os has all the possibilities to run as quickly
>as possible?
>

I don't know about Windows, especially not about 2012 R2, whatever that
is =)  But I remember that with some version, you had to supply it as
separate sockets (e.g. <topology sockets='24' cores='1' threads='1'/>),
but I'm not sure what version was that.

Anyway, you should be able to provide all the CPUs to the guest, however
bear in mind that the host will need some processing power as well, so
the best practice is to keep some CPU power for the host.  If you need
as much power as possible, make sure you use all the tuning (pinning,
backing) that's available for you [1] and benchmark the performance.

Martin

[1] https://libvirt.org/formatdomain.html
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