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---
features:
- |
Compute nodes using the libvirt driver can now report ``PCPU`` inventory.
This is consumed by instances with dedicated (pinned) CPUs. This can be
configured using the ``[compute] cpu_dedicated_set`` config option. The
scheduler will automatically translate the legacy ``hw:cpu_policy`` flavor
extra spec or ``hw_cpu_policy`` image metadata property to ``PCPU``
requests, falling back to ``VCPU`` requests only if no ``PCPU`` candidates
are found. Refer to the help text of the ``[compute] cpu_dedicated_set``,
``[compute] cpu_shared_set`` and ``vcpu_pin_set`` config options for more
information.
- |
Compute nodes using the libvirt driver will now report the
``HW_CPU_HYPERTHREADING`` trait if the host has hyperthreading. The
scheduler will automatically translate the legacy ``hw:cpu_thread_policy``
flavor extra spec or ``hw_cpu_thread_policy`` image metadata property to
either require or forbid this trait.
- |
A new configuration option, ``[compute] cpu_dedicated_set``, has been
added. This can be used to configure the host CPUs that should be used for
``PCPU`` inventory. Refer to the help text of the ``[compute]
cpu_dedicated_set`` config option for more information.
- |
The ``[compute] cpu_shared_set`` configuration option will now be used to
configure the host CPUs that should be used for ``VCPU`` inventory,
replacing the deprecated ``vcpu_pin_set`` option. Refer to the help text of
the ``[compute] cpu_shared_set`` config option for more infomration.
- |
A new configuration option, ``[workarounds] disable_fallback_pcpu_query``,
has been added. When creating or moving pinned instances, the scheduler will
attempt to provide a ``PCPU``-based allocation, but can also fallback to a legacy
``VCPU``-based allocation. This fallback behavior is enabled by
default to ensure it is possible to upgrade without having to modify compute
node configuration, but it results in an additional request for allocation
candidates from placement. This can have a slight performance impact and is
unnecessary on new or upgraded deployments where all compute nodes have been
correctly configured to report ``PCPU`` inventory. The ``[workarounds]
disable_fallback_pcpu_query`` config option can be used to disable this
fallback allocation candidate request, meaning only ``PCPU``-based
allocation candidates will be retrieved. Refer to the help text of the
``[workarounds] disable_fallback_pcpu_query`` config option for more
information.
deprecations:
- |
The ``vcpu_pin_set`` configuration option has been deprecated. You should
migrate host CPU configuration to the ``[compute] cpu_dedicated_set`` or
``[compute] cpu_shared_set`` config options, or both. Refer to the help
text of these config options for more information.
upgrade:
- |
Previously, if the ``vcpu_pin_set`` configuration option was not defined,
the libvirt driver would count all available host CPUs when calculating
``VCPU`` inventory, regardless of whether those CPUs were online or not.
The driver will now only report the total number of online CPUs. This
should result in fewer build failures on hosts with offlined CPUs.
- |
Previously, if an instance was using the ``isolate`` CPU thread policy on a
host with SMT (hyperthreading) enabled, the libvirt driver would fake a
non-SMT host by marking the thread sibling(s) for each host CPU used by the
instance as reserved and unusable. This is no longer the case. Instead,
instances using the policy will be scheduled only to hosts that do not
report the ``HW_CPU_HYPERTHREADING`` trait. If you have workloads that
require the ``isolate`` policy, you should configure some or all of your
hosts to disable SMT.
|
