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Re: [Xen-devel] RFC: Still TODO for 4.2? xl domain numa memory allocation vs xm/xend

On Fri, 2012-01-20 at 17:32 +0000, Dario Faggioli wrote:
> On Fri, 2012-01-20 at 16:54 +0000, Ian Campbell wrote: 
> > I confused myself into thinking that cpupools ~= NUMA because I've only
> > used cpupool-numa-split but I can see that you might also divide your
> > cpus up some other way.
> > 
> Yeah, indeed, although the numa-split case looks like the most useful
> one to me.
> > Should that same union be used for d->node_affinity though? It seems
> > like it would make sense.
> > 
> According to me, it should.

I agree.

One idea I had over the weekend is that we could support a special
'cpus="pool"' syntax to mean "pin this guest to the node I configured it
to be in". I think this is a second best option to simply having
d->node_affinity reflect the pool though.

>  Then, at least right now, moving it would
> probably kill its performances because all its memory will be far away,
> while right now it's all more "stochastic".

Yes, in some sense the xend behaviour is best case good behaviour and
worse case bad behaviour, while xl has a more average/consistent
behaviour across the range. In practice however I suspect xend probably
hits the good cases more often than not.

> Still, I think it should be done, as if you place a domain in a cpupool
> at its creation, I think the case of moving it away from there would be
> quite rare.



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