openstack/nova
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doc: Don't confuse CPU pinning/NUMA as Hyper-V only

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A recent'ish change in openstack-manuals [1] noted the new support for
NUMA topologies when using the Hyper-V driver. As part of this change, a
section was added that describes the configuration steps that were
necessary on Hyper-V hosts before booting instances. However, the way
this section is integrated gives the impression that NUMA support is a
Hyper-V only feature.

Correct this by moving this configuration step to the end of the
document and instead opting to link to it from higher in the doc.

[1] https://review.openstack.org/#/c/424102/

Change-Id: Ic8d9c1b35d52a26374763b5c0e4be79875814569
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>
This commit is contained in:
Stephen Finucane 2017-10-03 13:47:22 +01:00 committed by Matt Riedemann
parent 88adde8bba
commit a2a01c4ace
1 changed files with 46 additions and 43 deletions
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89
doc/source/admin/cpu-topologies.rst
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@ -36,55 +36,14 @@ In OpenStack, SMP CPUs are known as *cores*, NUMA cells or nodes are known as
eight core system with Hyper-Threading would have four sockets, eight cores per
socket and two threads per core, for a total of 64 CPUs.
Configuring compute nodes for instances with NUMA placement policies
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hyper-V is configured by default to allow instances to span multiple NUMA
nodes, regardless if the instances have been configured to only span N NUMA
nodes. This behaviour allows Hyper-V instances to have up to 64 vCPUs and 1 TB
of memory.
Checking NUMA spanning can easily be done by running this following powershell
command:
.. code-block:: console
(Get-VMHost).NumaSpanningEnabled
In order to disable this behaviour, the host will have to be configured to
disable NUMA spanning. This can be done by executing these following
powershell commands:
.. code-block:: console
Set-VMHost -NumaSpanningEnabled $false
Restart-Service vmms
In order to restore this behaviour, execute these powershell commands:
.. code-block:: console
Set-VMHost -NumaSpanningEnabled $true
Restart-Service vmms
The ``vmms`` service (Virtual Machine Management Service) is responsible for
managing the Hyper-V VMs. The VMs will still run while the service is down
or restarting, but they will not be manageable by the ``nova-compute``
service. In order for the effects of the Host NUMA spanning configuration
to take effect, the VMs will have to be restarted.
Hyper-V does not allow instances with a NUMA topology to have dynamic
memory allocation turned on. The Hyper-V driver will ignore the configured
``dynamic_memory_ratio`` from the given ``nova.conf`` file when spawning
instances with a NUMA topology.
Customizing instance NUMA placement policies
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. important::
The functionality described below is currently only supported by the
libvirt/KVM and Hyper-V driver.
libvirt/KVM and Hyper-V driver. The Hyper-V driver may require :ref:`some
host configuration <configure-hyperv-numa>` for this to work.
When running workloads on NUMA hosts, it is important that the vCPUs executing
processes are on the same NUMA node as the memory used by these processes.
@ -384,6 +343,50 @@ topologies that might, for example, incur an additional licensing fees.
For more information about image metadata, refer to the `Image metadata`_
guide.
.. _configure-hyperv-numa:
Configuring Hyper-V compute nodes for instance NUMA policies
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hyper-V is configured by default to allow instances to span multiple NUMA
nodes, regardless if the instances have been configured to only span N NUMA
nodes. This behaviour allows Hyper-V instances to have up to 64 vCPUs and 1 TB
of memory.
Checking NUMA spanning can easily be done by running this following PowerShell
command:
.. code-block:: console
(Get-VMHost).NumaSpanningEnabled
In order to disable this behaviour, the host will have to be configured to
disable NUMA spanning. This can be done by executing these following
PowerShell commands:
.. code-block:: console
Set-VMHost -NumaSpanningEnabled $false
Restart-Service vmms
In order to restore this behaviour, execute these PowerShell commands:
.. code-block:: console
Set-VMHost -NumaSpanningEnabled $true
Restart-Service vmms
The *Virtual Machine Management Service* (*vmms*) is responsible for managing
the Hyper-V VMs. The VMs will still run while the service is down or
restarting, but they will not be manageable by the ``nova-compute`` service. In
order for the effects of the host NUMA spanning configuration to take effect,
the VMs will have to be restarted.
Hyper-V does not allow instances with a NUMA topology to have dynamic
memory allocation turned on. The Hyper-V driver will ignore the configured
``dynamic_memory_ratio`` from the given ``nova.conf`` file when spawning
instances with a NUMA topology.
.. Links
.. _`Image metadata`: https://docs.openstack.org/image-guide/image-metadata.html
.. _`discussion`: http://lists.openstack.org/pipermail/openstack-dev/2016-March/090367.html