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Re: [Xen-users] query memory allocation per NUMA node

On Mon, 2017-02-06 at 12:15 +0000, anshul makkar wrote:
> On 12/01/17 00:58, Dario Faggioli wrote:
> > On Tue, 2017-01-10 at 01:50 +0000, Kun Cheng wrote:
> > > 
> > Yes, I remember talking with you about this, but I do not remember
> > that
> > the showstopper was knowing how many pages of a certain domain are
> > allocated on a certain NUMA node. That is quite straightforward to
> > tell
> > and, at present, never changes after domain creation!
>  I think number of pages allocated to a domain on a node does change
> during domain's runtime.
> Thats what the balloon driver in guest is all about. When ballooning
> out pages are taken from guest and its mfns marked as invalid.
Ah, yes, of course.

I wanted to make it clear that there's no memory migration or balancing
as a consequence of from where the memory itself is accessed, or
anything like that, and forgot to consider ballooning.

Indeed, when a page allocated to a guest from node 0 is ballooned out,
it is possible that, in future, when ballooning back up, the same
(guest) address will be backed by a page on node 3 (although, it will
most likely come again from a node in the domain's node affinity, if
there's space for it there).

Thanks for pointing this out. :-)

<<This happens because I choose it to happen!>> (Raistlin Majere)
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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