[openstack-dev] [nova] Running large instances with CPU pinning and OOM

Chris Friesen chris.friesen at windriver.com
Wed Sep 27 14:56:21 UTC 2017

On 09/27/2017 03:12 AM, Jakub Jursa wrote:
> On 27.09.2017 10:40, Blair Bethwaite wrote:
>> On 27 September 2017 at 18:14, Stephen Finucane <sfinucan at redhat.com> wrote:
>>> What you're probably looking for is the 'reserved_host_memory_mb' option. This
>>> defaults to 512 (at least in the latest master) so if you up this to 4192 or
>>> similar you should resolve the issue.
>> I don't see how this would help given the problem description -
>> reserved_host_memory_mb would only help avoid causing OOM when
>> launching the last guest that would otherwise fit on a host based on
>> Nova's simplified notion of memory capacity. It sounds like both CPU
>> and NUMA pinning are in play here, otherwise the host would have no
>> problem allocating RAM on a different NUMA node and OOM would be
>> avoided.
> I'm not quite sure if/how OpenStack handles NUMA pinning (why is VM
> being killed by OOM rather than having memory allocated on different
> NUMA node). Anyway, good point, thank you, I should have a look at exact
> parameters passed to QEMU when using CPU pinning.

OpenStack uses strict memory pinning when using CPU pinning and/or memory 
hugepages, so all allocations are supposed to be local.  When it can't allocate 
locally, it triggers OOM.


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