openstack/nova
Code Issues Proposed changes

Add documentation for emulator threads policy

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cpu-topologies documentation should contain configuration
for emulator threads policy

Change-Id: I420cc7fe618513dbadc5542b358c9f96860c67db
Closes-Bug: #1779924
This commit is contained in:
Andreas Karis 2018-07-03 15:16:37 -04:00
parent 34956bea4b
commit 69bb7adeec
1 changed files with 43 additions and 0 deletions
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doc/source/admin/cpu-topologies.rst
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@ -244,6 +244,49 @@ an exception will be raised.
For more information about image metadata, refer to the `Image metadata`_
guide.
Customizing instance emulator thread pinning policies
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When guests need dedicated vCPU allocation, it may not be acceptable to allow
emulator threads to steal time from real-time vCPUs.
In order to achieve emulator thread pinning, configure the
``hw:emulator_threads_policy`` flavor extra spec. Additionally,
``hw:cpu_policy`` needs to be set to ``dedicated``. The default value for
``hw:emulator_threads_policy`` is ``share``.
If you want to tell nova to reserve a dedicated CPU per instance for emulator
thread pinning, configure ``hw:emulator_threads_policy`` as ``isolate``.
.. code-block:: console
$ openstack flavor set m1.large \
--property hw:cpu_policy=dedicated \
--property hw:emulator_threads_policy=isolate
An instance spawned with these settings will have a dedicated physical CPU
which is chosen from the ``vcpu_pin_set`` in addition to the physical CPUs
which are reserved for the vCPUs.
If you want to tell nova to pin the emulator threads to a shared set of
dedicated CPUs, configure ``hw:emulator_threads_policy`` as ``share``.
.. code-block:: console
$ openstack flavor set m1.large \
--property hw:cpu_policy=dedicated \
--property hw:emulator_threads_policy=share
Additionally, set ``[compute]/cpu_shared_set`` in ``/etc/nova/nova.conf`` to
the set of host CPUs that should be used for best-effort CPU resources.
.. code-block:: console
# crudini --set /etc/nova/nova.conf compute cpu_shared_set 4,5,8-11
For more information about the syntax for ``hw:emulator_threads_policy``,
refer to the :doc:`/admin/flavors` guide.
Customizing instance CPU topologies
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~