openstack/glance
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Merge "Document hw_cpu_policy and hw_cpu_thread_policy image properties"

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Zuul 2018-08-08 20:01:05 +00:00 committed by Gerrit Code Review
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doc/source/admin/useful-image-properties.rst
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@ -276,6 +276,48 @@ Here is a list of useful image properties and the values they expect.
- ``hw_cpu_threads``
- The preferred number of threads to expose to the guest.
- Integer.
* - libvirt API driver
- ``hw_cpu_policy``
- Used to pin the virtual CPUs (vCPUs) of instances to the host’s
physical CPU cores (pCPUs). Host aggregates should be used to separate
these pinned instances from unpinned instances as the latter will not
respect the resourcing requirements of the former.
- * ``shared`` - (default) The guest vCPUs will be allowed to freely float
across host pCPUs, albeit potentially constrained by NUMA policy.
* ``dedicated`` - The guest vCPUs will be strictly pinned to a set of
host pCPUs. In the absence of an explicit vCPU topology request, the
drivers typically expose all vCPUs as sockets with one core and one
thread. When strict CPU pinning is in effect the guest CPU topology
will be setup to match the topology of the CPUs to which it is pinned.
This option implies an overcommit ratio of 1.0. For example, if a two
vCPU guest is pinned to a single host core with two threads, then the
guest will get a topology of one socket, one core, two threads.
* - libvirt API driver
- ``hw_cpu_thread_policy``
- Further refine ``hw_cpu_policy=dedicated`` by stating how hardware CPU
threads in a simultaneous multithreading-based (SMT) architecture be
used. SMT-based architectures include Intel processors with
Hyper-Threading technology. In these architectures, processor cores
share a number of components with one or more other cores. Cores in
such architectures are commonly referred to as hardware threads, while
the cores that a given core share components with are known as thread
siblings.
- * ``prefer`` - (default) The host may or may not have an SMT
architecture. Where an SMT architecture is present, thread siblings
are preferred.
* ``isolate`` - The host must not have an SMT architecture or must
emulate a non-SMT architecture. If the host does not have an SMT
architecture, each vCPU is placed on a different core as expected. If
the host does have an SMT architecture - that is, one or more cores
have thread siblings - then each vCPU is placed on a different
physical core. No vCPUs from other guests are placed on the same core.
All but one thread sibling on each utilized core is therefore
guaranteed to be unusable.
* ``require`` - The host must have an SMT architecture. Each vCPU is
allocated on thread siblings. If the host does not have an SMT
architecture, then it is not used. If the host has an SMT
architecture, but not enough cores with free thread siblings are
available, then scheduling fails.
* - libvirt API driver
- ``hw_disk_bus``
- Specifies the type of disk controller to attach disk devices to.