Hi Nick,

Setting CPU Shares only changes how the instance works. It does not affect the current workload unless the instance is under pressure.

For example, if you are running an RDBMS, you may see a performance improvement when normalizing the database or generating a monthly report. Even that, the improvement may be minimum.

Do not expect a sensible performance improvement for normal operation.

Performance tuning is not magic. You will often perform many configurations to see a 1%, maybe 2% gain.

Regards,

Marcos

From: Nick --- <jsmith1299@live.com>
Sent: Wednesday, February 1, 2023 9:59 AM
To: users@ovirt.org
Subject: [External] : [ovirt-users] CPU Shares

Hello,

I would like some help understanding CPU shares. We have several VMs which are CPU pinned due to licensing. We would like to favor one VM since it is our application VM over the other VMs which it is pinned with. Would I set the CPU share on the one that needs to priority to high or low?

In the documentation I see the following:

Specify CPU Shares. Possible options are Low, Medium, High, Custom, and Disabled. Virtual machines set to High receive twice as many shares as Medium, and virtual machines set to Medium receive twice as many shares as virtual machines set to Low. Disabled instructs VDSM to use an older algorithm for determining share dispensation; usually the number of shares dispensed under these conditions is 1020.

I currently have it set to high and I believe it is doing the opposite of what I want it to do as the CPU steal percentage appears to be 10-15% over the other VMs which show no CPU steal and are set to low. I'd like to confirm if I have this setup correctly or not.

Thanks,

Nick