Open Stack

On 07/17/2015 07:28 AM, Daniel P. Berrange wrote:
> On Fri, Jul 17, 2015 at 06:58:46AM -0600, David Medberry wrote:
>> HI Daniel,
>>
>> Yep found that all out.
>>
>> Now I'm struggling through the NUMA mismatch. NUMA as there are two cpus.
>> The old CPU was a 10 core 20 thread thus 40 "cpus", {0-9,20-29} and then
>> {10-19,30-39} on the other cell. The new CPU is a 12 core 24 thread.
>> Apparently even in kilo, this results in a mismatch if I'm running a 2 VCPU
>> guest and trying to migrate from new to old. I suspect I have to disable
>> NUMA somehow (filter, etc) but it is entirely non-obvious. And of course
>> I'm doing this again in OpenStack nova (not direct libvirt) so I'm going to
>> do a bit more research and then file a new bug. This also may be fixed in
>> Kilo but I"m not finding it (and it may be fixed in Liberty already and
>> just need a backport.)
>>
>> My apologies for not following up to the list once I found the Kilo
>> solution to the original problem.
>
> The fact that Nova doesn't rewrite numa topology on migrate is a known
> bug which Nikola is working on fixing in Liberty. IIRC, you ought to be
> able to avoid it by just disabling the NUMA schedular filter.

I wonder if this is due to the "isolate an instance on a numa node" work 
combined with the fact that numa topology doesn't get rewritten.  If so, it 
might be "fixed" by commit 41ba203 on stable/kilo.

If the guest is using dedicated CPUs then there's no fix, it's just broken for 
live/cold migration, resize, and evacuate.

Chris