[kata-dev] Performance isolation: expectations for number of CPUs

Jens Freimann jfreiman at redhat.com
Wed Jul 7 20:46:06 UTC 2021


On Wed, Jul 7, 2021 at 12:48 PM Christophe de Dinechin
<dinechin at redhat.com> wrote:
> On 2021-07-07 at 01:31 UTC, "Adams, Eric" <eric.adams at intel.com> wrote...
> > Christophe,
> > 2) I also observed that Pod Overhead isn't used in the calculation for
> > hotplugged CPU's.
>
> That seems correct. The pod overhead accounts for the overhead "outside" the
> VM, i.e. virtiofsd, qemu's own memory needs, the extra cost of doing I/Os,
> etc. So this is additional resources the host needs, not the VM.

This is very counter-intuitive and also doesn't fit the 'Motivation'
section in the original
design[1]. Wouldn't this lead to wrong results for the resource quota
and scheduler calculations?

[1] https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/688-pod-overhead

regards
Jens




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