On Thu, Oct 13, 2011 at 12:53:22PM +0100, Daniel P. Berrange wrote:
On Mon, Oct 03, 2011 at 03:28:44PM +0530, Bharata B Rao wrote:
Hi,
I discussed the possibilities of adding NUMA topology XML specification support for guests here some time back. Since my latest proposal (http://permalink.gmane.org/gmane.comp.emulators.libvirt/44626) didn't get any response, I am posting a prototype implementation that supports specifying NUMA topology for QEMU guests.
- The implementation is based on the last proposal I listed above.
So we're basically only allowing a flat NUMA toplogy
<numa> <node cpus='0,2,4,6' mems='1024> <node cpus='8,10,12,14' mems='1024> <node cpus='1,3,5,7' mems='1024'> <node cpus='9,11,13,15' mems='1024'> </numa>
which mirrors what QEMU allows currently. Should we need to support a hierarchy, we can trivially extend this syntax in a backwards compatible fashion
<numa> <node> <node cpus='0,2,4,6' mems='1024> <node cpus='8,10,12,14' mems='1024> </node> <node> <node cpus='1,3,5,7' mems='1024'> <node cpus='9,11,13,15' mems='1024'> </node> </numa>
so I think this limitation is OK for now.
Fine then.
In the virsh capabilities XML, we actually use the word 'cell' rather than 'node'. I think it might be preferrable to be consistent and use 'cell' here too.
I feel NUMA node sounds more familiar than NUMA cell. But if libvirt prefers cell, we can go with cell I suppose.
- The implementation is for QEMU only.
That's fine.
- The patchset has gone through extremely light testing and I have just tested booting a 2 socket 2 core 2 thread QEMU guest. - I haven't really bothered to cover all the corner cases and haven't run libvirt tests after this patchset. For eg, there is no code to validate if the CPU combination specified by <topology> and <numa> match with each other. I plan to cover all these after we freeze the specification itself.
ok
WRT the question about CPU enumeration order in the URL quoted above. I don't think it matters whether we enumerate CPUs in the same order as real hardware. The key thing is that we just choose an order, document what *our* enumeration order is, and then stick to it forever.
Ok fine. Regards, Bharata.