[nova] NUMA scheduling

Eric K. Miller emiller at genesishosting.com
Fri Oct 16 22:49:40 UTC 2020


Hi,

 

I'm at a loss for finding good information about how a VM's vCPUs and
Memory are assigned to NUMA nodes within a scheduled physical host.  I
think Libvirt does this, and the Nova Scheduler simply finds the right
physical host to run the VM, and thus Nova has no input on which NUMA
node to choose.  So this might be a Libvirt question.

 

We are running Stein and have the issue where VMs launch on NUMA Node 0,
and not on NUMA Node 1, in physical hosts with two processors, and are
simply looking for a way to tell Libvirt to consider NUMA Node 1 when
scheduling a VM, since there is nearly all of the memory available on
NUMA Node 1.

 

Our flavors are defined with hw:numa_nodes='1' since we want all
vCPUs+Memory to land on a single NUMA Node, and so the guest OS has
visibility that a single NUMA Node is being used.

 

We are "not" looking for a way to pin a VM to a specific NUMA node (such
as for SR-IOV purposes).

 

Any suggestions where to look for the solution?

 

Thanks!


Eric

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