Re: Thoughts on simple scanner approach for free page hinting

[Michael S. Tsirkin]

On Tue, Apr 09, 2019 at 03:36:08PM +0200, David Hildenbrand wrote:
> On 09.04.19 15:31, Michael S. Tsirkin wrote:
> > On Tue, Apr 09, 2019 at 11:20:36AM +0200, David Hildenbrand wrote:
> >> BTW I like the idea of allocating pages that have already been hinted as
> >> last "choice", allocating pages that have not been hinted yet first.
> > 
> > OK I guess but note this is just a small window during which
> > not all pages have been hinted.
> 
> Yes, good point. It might sound desirable but might be completely
> irrelevant in practice.
> 
> > 
> > So if we actually think this has value then we need
> > to design something that will desist and not drop pages
> > in steady state too.
> 
> By dropping, you mean dropping hints of e.g. MAX_ORDER - 1 or e.g. not
> reporting MAX_ORDER - 3?

I mean the issue is host unmaps the pages from guest right?  That is
what makes hinted pages slower than non-hinted ones.  If we do not want
that to happen for some pages, then either host can defer acting on the
hint, or we can defer hinting.

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