Re: [libvirt] [RFC PATCH 0/3] Guest NUMA topology support - v0
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.
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.
- 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.
Regards,
Daniel
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