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

[Dario Faggioli <dario.faggioli@citrix.com>]

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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@citrix.com> 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,
Dario

-- 
<<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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