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Thank you for the clarification Christophe!

On Wed, Jul 28, 2021 at 3:42 PM Christophe de Dinechin
<dinechin at redhat.com> wrote:
>
> Late follow-up after a discussion with Jens about a different document pointed out that my answer was ambiguous and easy to misinterpret.
>
> > On 7 Jul 2021, at 22:46, Jens Freimann <jfreiman at redhat.com> wrote:
> >
> > 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.
>
> That wording be interpreted as the pod overhead _only_ accounting for overhead outside the VM. That is not what I intended. I intended to point out that it _also_ accounts for overhead outside the VM. In other words, it is the sum of how much memory the VM needs just to get started (e.g. 110M for a basic kernel, 300M for a more standard RHEL-style kernel), which includes the memory used by the agent, and of additional processes outside the VM, like virtiofsd, the shim, etc.
>
>
> >
> > 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
> >
>