[openstack-dev] [nova] Running large instances with CPU pinning and OOM
chris.friesen at windriver.com
Thu Sep 28 14:45:40 UTC 2017
On 09/28/2017 05:29 AM, Sahid Orentino Ferdjaoui 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.
What I see in the code/docs doesn't match that, but it's entirely possible I'm
nova uses LibvirtConfigGuestNUMATuneMemory with a mode of "strict" and a nodeset
of "the host NUMA nodes used by a guest".
For a guest with single NUMA node, I think this would map to libvirt XML of
<memory mode="strict" nodeset="1"/>
The docs at https://libvirt.org/formatdomain.html#elementsNUMATuning say, "The
optional memory element specifies how to allocate memory for the domain process
on a NUMA host."
That seems to me that the qemu overhead would be NUMA-affined, no? (If you had
a multi-NUMA-node guest, then the qemu overhead would float across all the NUMA
nodes used by the guest.)
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