12:55 p.m.
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 ?
Thank you for any information that can enlighthen us, since we are worried that we are
suffering from bad performance due to naive cpu configuration choices.
12:59 p.m.
nelson.lameiras(a)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
Thank you for any information that can enlighthen us, since we are
worried that we are suffering from bad performance due to naive cpu
configuration choices.
3:29 p.m.
Based on my experience, just set 1 thread:1core:as many sockets you need.
You can still match the vortual sockets to numa nodes, butlater it will bwcome harder as
most probably the Hypervisor won't be dedicated to the VM.
Best Regards,Strahil Nikolov
On Fri, Jul 30, 2021 at 13:00, Milan Zamazal<mzamazal(a)redhat.com> wrote:
nelson.lameiras(a)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
Thank you for any information that can enlighthen us, since we are
worried that we are suffering from bad performance due to naive cpu
configuration choices.
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6:04 p.m.
I guess it's pretty obvious that I miss my qwerty hardware keyboard :D
Best Regards,Strahil Nikolov
On Fri, Jul 30, 2021 at 15:31, Strahil Nikolov via Users<users(a)ovirt.org> wrote:
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1025
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1026
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3 comments
3 participants
participants (3)
-
Milan Zamazal -
nelson.lameiras＠lyra-network.com -
Strahil Nikolov