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Re: [Xen-devel] PV Shim ballooning

On Tue, Feb 11, 2020 at 05:29:09PM +0000, Igor Druzhinin wrote:
> On 11/02/2020 16:42, Roger Pau Monné wrote:
> > On Tue, Feb 11, 2020 at 04:29:36PM +0000, Igor Druzhinin wrote:
> >> Agree. But as I said I'm not aware of any guest that violates the
> >> invariant of decrease_reservation() being the last call.
> > 
> > Maybe we could piggyback on whether a page is removed from the domain
> > domheap and use that as a signal that the page should be ballooned
> > out?
> > 
> > There's already an arch_free_heap_page that's called when a page is
> > removed from a domain, which might be suitable for this. It would
> > however imply making an hypercall for every page to be ballooned out.
> I tested that - doesn't work - too many hypercalls make ballooning take
> ages. This simply cannot be done on page-by-page basis.

Why not place them on a list (in arch_free_heap_page) and do the flush
either after a timeout or when it gets to a certain number of


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