docs/doc/source/admintasks/isolating-cpu-cores-to-enhance-application-performance.rst

.. bew1572888575258
.. _isolating-cpu-cores-to-enhance-application-performance:

========================================================
Isolate the CPU Cores to Enhance Application Performance
========================================================

|prod| supports running the most critical low-latency applications on host CPUs
which are completely isolated from the host process scheduler.

This allows you to customize Kubernetes CPU management when policy is set to
static so that low-latency applications run with optimal efficiency.

The following restrictions apply when using application-isolated cores in the
Horizon Web interface and sysinv:

-   There must be at least one platform and one application core on each host.

    .. warning::
        The presence of an application core on the node and nodes missing this
        configuration will fail.


For example:

.. code-block:: none

    ~(keystone)admin)$ system host-lock worker-1
    ~(keystone)admin)$ system host-cpu-modify  -f platform -p0 1 worker-1
    ~(keystone)admin)$ system host-cpu-modify  -f application-isolated -p0 15 worker-1
    ~(keystone)admin)$ system host-cpu-modify  -f application-isolated -p1 15 worker-1
    ~(keystone)admin)$ system host-unlock worker-1

All SMT siblings on a core will have the same assigned function. On host boot,
any CPUs designated as isolated will be specified as part of the isolcpu kernel
boot argument, which will isolate them from the process scheduler.

.. only:: partner

    .. include:: /_includes/isolating-cpu-cores-to-enhance-application-performance.rest
       :start-after: usage-limitation-begin
       :end-before: usage-limitation-end

When using the static CPU manager policy before increasing the number of
platform CPUs or changing isolated CPUs to application CPUs on a host, ensure
that no pods on the host are making use of any isolated CPUs that will be
affected. Otherwise, the pod\(s\) will transition to a Topology Affinity Error
state. Although not strictly necessary, the simplest way to do this on systems
other than AIO Simplex is to administratively lock the host, causing all the
pods to be restarted on an alternate host, before changing CPU assigned
functions. On AIO Simplex systems, you must explicitly delete the pods.

.. only:: partner

   .. include:: /_includes/isolating-cpu-cores-to-enhance-application-performance.rest
      :start-after: changes-relative-to-root-begin
      :end-before: changes-relative-to-root-end