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

Sahid Orentino Ferdjaoui sferdjao at redhat.com
Fri Sep 29 12:08:25 UTC 2017

On Thu, Sep 28, 2017 at 11:10:38PM +0200, Premysl Kouril wrote:
> >
> > Only the memory mapped for the guest is striclty allocated from the
> > NUMA node selected. The QEMU overhead should float on the host NUMA
> > nodes. So it seems that the "reserved_host_memory_mb" is enough.
> >
> Even if that would be true and overhead memory could float in NUMA
> nodes it generally doesn't prevent us from running into OOM troubles.
> No matter where (in which NUMA node) the overhead memory gets
> allocated, it is not included in available memory calculation for that
> NUMA node when provisioning new instance and thus can cause OOM (once
> the guest operating system  of the newly provisioned instance actually
> starts allocating memory which can only be allocated from its assigned
> NUMA node).

That is why you need to use Huge Pages. The memory will be reserved
and locked for the guest.

> Prema
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