instances always packed to NUMA node 0

[Rafael Folco]

Description
===========
Instances are packed into node0, always. NUMA placement criteria is undefined when not using CPU pinning and hw:numa_nodes=1.

Steps to reproduce
==================
Create a flavor w/ hw:numa_nodes=1 (hw:cpu_policy unset)

Spawn multiple instances

Check nodeset in the instance XML

Expected result
===============

Use all NUMA nodes by applying some NUMA placement criteria: Spread, pack or random

Actual result
=============
Only node 0 is used. All others are unused.

Environment
===========

Ubuntu Xenial 16.10, OpenStack Mitaka release, Libvirt 1.3.1

Note: This issue has been found / tested on Ubuntu KVM on Power (ppc64le arch), however, it affects all architectures.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/340569

[Daniel Berrange (berrange)]

Nova fully fills each node before considering placing a guest on the next node. This isn't a bug - its expected behaviour intended to maximise number of guests that can be packed onto each compute host. If you want to suggest alternative strategies please submit a blueprint + spec with the proposed design & rational

[Rafael Folco (rafaelfolco)]

This bug can be reproduced with:
NUMATopologyFilter unset OR --availability-zone zone:host
AND
hw:cpu_policy unset AND hw:numa_nodes=1

The problem in skipping filter logic is discussed here:
https://bugs.launchpad.net/nova/+bug/1427772
http://lists.openstack.org/pipermail/openstack-dev/2015-February/056695.html

The side effects for NUMA placement is also reported here:
https://bugzilla.redhat.com/show_bug.cgi?id=1189906

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/346133

[OpenStack Infra (hudson-openstack)]

Change abandoned by Rafael Folco (<email address hidden>) on branch: master
Review: https://review.openstack.org/340569
Reason: in favor of https://review.openstack.org/346133

[OpenStack Infra (hudson-openstack)]

Change abandoned by Rafael Folco (<email address hidden>) on branch: master
Review: https://review.openstack.org/346133

[Gustavo Randich (gustavo-randich)]

I look forward to a solution for this issue, because we use an in-house/custom-made scheduler, forcing the individual host to boot the VM on via availability-zone nova:host, but still need to spread the load across NUMA nodes for flavors with hw:numa_nodes=1