ae2e5650d1
Live migration is currently totally broken if a NUMA topology is present. This affects everything that's been regrettably stuffed in with NUMA topology including CPU pinning, hugepage support and emulator thread support. Side effects can range from simple unexpected performance hits (due to instances running on the same cores) to complete failures (due to instance cores or huge pages being mapped to CPUs/NUMA nodes that don't exist on the destination host). Until such a time as we resolve these issues, we should alert users to the fact that such issues exist. A workaround option is provided for operators that _really_ need the broken behavior, but it's defaulted to False to highlight the brokenness of this feature to unsuspecting operators. Change-Id: I217fba9138132b107e9d62895d699d238392e761 Signed-off-by: Stephen Finucane <sfinucan@redhat.com> Related-bug: #1289064
26 lines
1.3 KiB
YAML
26 lines
1.3 KiB
YAML
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upgrade:
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Live migration of instances with NUMA topologies is now disabled by default
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when using the libvirt driver. This includes live migration of instances
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with CPU pinning or hugepages. CPU pinning and huge page information for
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such instances is not currently re-calculated, as noted in `bug #1289064`_.
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This means that if instances were already present on the destination host,
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the migrated instance could be placed on the same dedicated cores as these
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instances or use hugepages allocated for another instance. Alternately, if
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the host platforms were not homogeneous, the instance could be assigned to
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non-existent cores or be inadvertently split across host NUMA nodes.
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The `long term solution`_ to these issues is to recalculate the XML on the
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destination node. When this work is completed, the restriction on live
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migration with NUMA topologies will be lifted.
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For operators that are aware of the issues and are able to manually work
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around them, the ``[workarounds] enable_numa_live_migration`` option can
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be used to allow the broken behavior.
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For more information, refer to `bug #1289064`_.
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.. _bug #1289064: https://bugs.launchpad.net/nova/+bug/1289064
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.. _long term solution: https://blueprints.launchpad.net/nova/+spec/numa-aware-live-migration
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