---
upgrade:
  - |
    A new config option has been added to the OpenvSwitch plugin
    ``[os_vif_ovs]default_qos_type``. This option controls
    the Default tc qdisc applied to a kernel interface attached to OpenvSwitch
    on Linux hosts. As of this release, the default tc qdisc is ``linux-noop``
    other supported values are ``linux-htb``, ``linux-hfsc``,
    ``linux-sfq``, ``linux-codel`` and  ``linux-fq_codel``.
    before this release the default qdisc was undefined. older kernels did not
    apply  /proc/sys/net/core/default_qdisc to tap devices. newer kernels such
    as the one found in rhel 9 do. This can significantly impact performance.
    See bug https://bugs.launchpad.net/os-vif/+bug/2017868 for more details.
    The default ``linux-noop`` should perform well for all use-cases so no
    explicit action is required on upgrade however it should be noted that
    the default_qos_type is only set when a port is first created. As such
    this fix will not take effect until the next time the vm interface is
    recreated. If you change this value for an existing port it will only
    take effect after a hard reboot of the VM or a move operation.

fixes:
  - |
    A significant performance regression was observed on a subset of Linux
    kernels and sysctl configurations resulting in a reduction of throughput
    to between 10% of the prior performance for small packets and 50% for
    large packets. This has now been resolved by setting a default
    qos_type on ovs interfaces when they are first created. To mimic libvirt's
    undocumented behavior the ``linux-noop`` type is set on the ovs port when
    it is first created. This will be overridden by neutron if a qos policy
    is defined for a port and is simply the initial value to use when first
    adding a port to OpenvSwitch. The default QoS type applied can be
    controlled by the ``[os_vif_ovs]default_qos_type`` config operation.
    See bug https://bugs.launchpad.net/os-vif/+bug/2017868 for more details.