From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: initial ballooning amount on HVM+PoD
Date: Mon, 20 Jan 2014 10:31:22 -0500
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To: Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>, xen-devel <xen-devel@lists.xenproject.org>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Keir Fraser <keir@xen.org>
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> >>>> Question now is: Considering that (a) is broken (and hard to fix)
> >>>> and (b) is in presumably a large part of practical cases leading to
> >>>> too much ballooning down, shouldn't we open up
> >>>> XENMEM_get_pod_target for domains to query on themselves?
> >>>> Alternatively, can anyone see another way to calculate a
> >>>> reasonably precise value?
> >>> I think hypervisor query is a good thing although I don't know whether
> >>> exposing PoD-specific data (count and entry_count) to the guest is
> >>> necessary. It's probably OK (or we can set these fields to zero for
> >>> non-privileged domains).
> >> That's pointless then - if no useful data is provided through the
> >> call to non-privileged domains, we can as well keep it erroring for
> >> them.
> >>
> > 
> > I thought that are after d->tot_pages, no?
> 
> That can be obtained through another XENMEM_ operation. No,
> what is needed is the difference between PoD entries and PoD
> cache (which then needs to be added to tot_pages).

Won't that be racy? Meaning the moment you get that information and
kick of the balloon worker, said value might be different already?

> 
> Jan