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Re: [Libvir] PATCH: Compatability with Xen 3.2.0

On Tue, Dec 18, 2007 at 01:03:24AM +0000, John Levon wrote:
> On Mon, Dec 17, 2007 at 07:19:04PM +0000, Daniel P. Berrange wrote:
> > In Xen 3.2.0 the  physinfo hypercall was changed to remove the field
> > 'sockets_per_node' and add in 'nr_cpus'. We use the sockets_per_node field
> > in livirt for the  virNodeInfo struct :-(  This patch re-calculates its
> > value in terms of 'nr_cpus / (nodes*cores*threads)' which is how older
> > Xen used to figure it out.
> I thought the whole point of that change was that the value was not
> correct in some cases? I admit I don't know what those cases were, but
> isn't this just re-introducing that incorrect information?

Yes & yes.

The scenario where it was wrong is where you have a big NUMA system where
not all sockets were populated.

At the same time though,  virNodeInfo is a part of the libvirt public ABI
and thus we have to put something in that field. So I'm choosing to continue
to the put information which matches the previous semantics, so we're no
worse off than we always were. 

If people really really need accurate info about CPU population, then the
new NUMA support in libvirt will give that correct info.

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