On Fri, Jul 30, 2021 at 13:00, Milan Zamazal
<mzamazal@redhat.com> wrote:
nelson.lameiras@lyra-network.com writes:
> Hello,
>
> We are currently running oVirt 4.3.10
> Our oVirt hypervisors (HV) have 2 cpu sockets * 6 cores * HT = 24 vcpu
> Our VMs (centos7) range globally from 2vcpu to 8vcpu
> oVirt allows to configure - per VM - the following 3 advanced
> parameters : virtual_sockets : cores_per_virtual_socket :
> threads_per_core
>
> We make sure that threads per core is always 1 (so no question there)
> But, for the other 2 parameters, we are unsure of the correct
> configuration, and if there is a performance penalty on bad
> configuration.
>
> Let's consider a 4vcpu VM
>
> 1- Is there a performance difference betwenn 1:4:1 and 4:1:1 configuration ?
> 2- When should we opt for one or another configuration ?
> 2- Our VMs total CPU provisionning sum is twice the hypervisors
> capacity, but they are mostly idle so it is not an issue, but can this
> influence configuration choice above ?
I'm not sure anybody knows an ultimate answer and/or a simple rule of
thumb. My guess would be that generally there should be no significant
difference. But there may be application specific considerations,
especially when NUMA or something similar is involved.
I think the best what can be done is to test both the configurations
with your particular applications and setup and see if any of them
provides a systematically better performance than the other one.
Regards,
Milan
https://lists.ovirt.org/archives/list/users@ovirt.org/message/4WUNPQ5WNUVJQAHAJTH4GAJYOTTYTIMB/