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Re: [Xen-devel] [RFC v2][PATCH 1/3] docs: design and intended usage for NUMA-aware ballooning

On mar, 2013-08-20 at 23:15 +0800, Li Yechen wrote:
> Hi David, 
> On Mon, Aug 19, 2013 at 8:58 PM, David Vrabel
> <david.vrabel@xxxxxxxxxx> wrote:
>         The physical NUMA topology must not be exposed to guests that
>         have a
> Most of you have the same option that the interface should be in Xen,
> not in Guest
> balloon. I'm agree with it. In next version I'll think of how to
> implement this interface
> between xen and balloon.  
Perfect. That is not that much different from what you already have, the
only bit that will need some rework is the ballooning up path (see
George's e-mails).

>         In general, I'm not keen on adding ABIs or interfaces that
>         don't solve
>         real world problems, particularly if they're easy to misuse
>         and end up
>         with something that is very suboptimal.
> Dario, could the test examples that you sent to me several month be
> represented
> as a real-word example?
> The example shows that, after several guests create and shut-up, the
> node
> affinity is a mess
They were not real-world example. As I said before, that is a
chicken-&-egg problem: there are not real world examples until we
implement the feature! :-P

What I think you're talking about is an old (2010 ?) Xen Summit
presentation from someone working on the same problem before, but then
not finishing it.

I don't have the link handy right now... I'll see if I can find it and
post it here.

> Oh, I think this is a better interface!
> I'd very appreciate this than what I have now. However, the code I
> show here
> _does_not_really_work_. It just pass some small tests. And I'm afraid
> that 
> there may be some bugs in my code.
> Could I set up David's interface as a secondary goal, waiting until
> this code
> is full tested? I'm really not that confident :)
EhEh... All code has bugs. :-)

As I said, I also like this interface more. However, what I think you
should concentrate on (apart from, of course, debugging) is producing a
version of the series which does not use any new xenstore keys/interface
at all, and just balloons up and down taking pages evenly from all the
guest's virtual NUMA nodes.

After that, we can come back to implement a more fine grained control,
probably via this interface David is proposing here.

What do you think?

Thanks and Regards,

<<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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