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

Premysl Kouril premysl.kouril at gmail.com
Thu Sep 28 21:10:38 UTC 2017

> 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).


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