Re: [Xen-devel] [Hackathon minutes] PV frontends/backends and NUMA machines

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.05.13 at 10:47, George Dunlap <George.Dunlap@xxxxxxxxxxxxx> wrote:
> On Tue, May 21, 2013 at 9:32 AM, Tim Deegan <tim@xxxxxxx> wrote:
>> At 14:48 +0100 on 20 May (1369061330), George Dunlap wrote:
>>> So the work items I remember are as follows:
>>> 1. Implement NUMA affinity for vcpus
>>> 2. Implement Guest NUMA support for PV guests
>>> 3. Teach Xen how to make a sensible NUMA allocation layout for dom0
>>
>> Does Xen need to do this?  Or could dom0 sort that out for itself after
>> boot?
> 
> There are two aspects of this.  First would be, if dom0.nvcpus <
> host.npcpus, to place the vcpus reasonably on the various numa nodes.
> 
> The second is to make the pfn -> NUMA node layout reasonable.  At the
> moment, as I understand it, pfns will be striped across nodes.  In
> theory dom0 could deal with this, but it seems like in practice it's
> going to be nasty trying to sort that stuff out.  It would be much
> better, if you have (say) 4 nodes and 4GiB of memory assigned to dom0,
> to have pfn 0-1G on node 0, 1-2G on node 2, &c.

I have been having a todo list item since around the release of 4.2
to add support for "dom0_mem=node<n>" and
"dom0_vcpus=node<n>" command line options, which I would think
would be sufficient to deal with that. Sadly, I never had enough
spare time to actually implement this.

Jan


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