Re: On guest free page hinting and OOM

Michael S. Tsirkin
2019-04-01T14:45:33Z

On Mon, Apr 01, 2019 at 04:09:32PM +0200, David Hildenbrand wrote:
> >
> > When you say yield, I would guess that would involve config space access
> > to the balloon to flush out outstanding hints?
>
> I rather meant yield your CPU to the hypervisor, so it can process
> hinting requests faster (like waiting for a spinlock). This is the
> simple case. More involved approaches might somehow indicate to the
> hypervisor to not process queued requests but simply return them to the
> guest so the guest can add the isolated pages to the buddy. If this is
> "config space access to the balloon to flush out outstanding hints" then
> yes, something like that might be a good idea if it doesn't harm
> performance.

The problem would be in testing this unfortunately. Same as any
OOM hack, it is difficult to test well.

> --
>
> Thanks,
>
> David / dhildenb