os-vif should provide a way to set a default qos qdisc on a ovs port to avoid regressions across kernel versions and configs.

[sean mooney]

in the past when hybrid_plug=true was set on a port libvirt would generate the XML using the bridge option with virtual <virtualport type='openvswitch'>

<interface type='bridge'>
  <source bridge='ovsbr'/>
  <virtualport type='openvswitch'>
    <parameters profileid='menial' interfaceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/>
  </virtualport>
</interface>

if hybrid_plug=false nova woudl generate
the XML without the <virtualport type='openvswitch'> element

  <interface type='bridge'>
    <source bridge='br1'/>
    <target dev='vnet7'/>
    <mac address="00:11:22:33:44:55"/>
  </interface>

a undocumented side effect of <virtualport type='openvswitch'> is that libvirt set the qdisc on the created tapp to linux-noop https://libvirt.org/formatdomain.html#bridge-to-lan

when we fixed https://bugs.launchpad.net/nova/+bug/1734320 by delegating port plugging to os vif we did this by changing the interface type generated by nova to ethernet.

<interface type='ethernet'>
    <target dev='mytap1' managed='no'/>
    <model type='virtio'/>
</interface>

https://libvirt.org/formatdomain.html#generic-ethernet-connection

as a result the undocumented side effect of the <virtualport type='openvswitch'> element now no longer takes effect for any ovs ports.

in more recent kernels or if you set a custom default qdisc vai sysctl this can lead to significant throughput reductions for kernel ovs. for small to medium packets this can reduce the throughput to as low as 10% of the previous behaviour and still have a 50% reduction for jumbo frames.

this is is a significant regression and should be corrected.

in the past this has likely accounted for some of the performance delta between hybrid_plug=true and hybrid_plug=false.

ovs provides a way to set the qdic as an option on the port which it will implement on the underlying netdev.

given the previously inconsistent nature we should ensure the same qdics is applied in both the hybrid_plug True or False case but we need to be careful to not set this for ovs ports on windows or vhost-user ports.

With the above context we should make the default qdisc configurable via a new os-vif config option as a pragmatic back portable solution. Eventually, we can work with Neutron to enable a more granular per port qdisc feature if desirable but that is out of scope of this bug.

[sean mooney (sean-k-mooney)]

just cross-reference our downstream tracker fo this since that is also public
https://issues.redhat.com/browse/OSPRH-183

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/os-vif/+/881751

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/os-vif/+/881751
Committed: https://opendev.org/openstack/os-vif/commit/c0d101aa81cff200e1db2a0746598b72e26748e4
Submitter: "Zuul (22348)"
Branch: master

commit c0d101aa81cff200e1db2a0746598b72e26748e4
Author: Sean Mooney <email address hidden>
Date: Tue May 9 19:52:48 2023 +0100

    set default qos policy

    This change modifies the os-vif ovs plugin to set a default
    tc qdisc on ovs interface when the host os is not windows
    and the system datapath is used.

    This change fixes a "silent" bug in the functional test code due
    to a change in an ovsdbapp function signiture to accpet a new paramater.

    Closes-Bug: #2017868
    Change-Id: Id9ef7074634a0f23d67a4401fa8fca363b51bb43

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/2023.1
Review: https://review.opendev.org/c/openstack/os-vif/+/883015

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/zed
Review: https://review.opendev.org/c/openstack/os-vif/+/883016

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/yoga
Review: https://review.opendev.org/c/openstack/os-vif/+/883071

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/yoga
Review: https://review.opendev.org/c/openstack/os-vif/+/886710

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/xena
Review: https://review.opendev.org/c/openstack/os-vif/+/886716

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/wallaby
Review: https://review.opendev.org/c/openstack/os-vif/+/886778

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/os-vif 3.2.0 release.

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Elod Illes <email address hidden>" on branch: stable/yoga
Review: https://review.opendev.org/c/openstack/os-vif/+/883071
Reason: Abandoning as this is a duplicate with a mismatching change ID. The proper cherry picks can be found with change ID: Id9ef7074634a0f23d67a4401fa8fca363b51bb43

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Elod Illes <email address hidden>" on branch: stable/yoga
Review: https://review.opendev.org/c/openstack/os-vif/+/886710
Reason: stable/yoga branch of openstack/os-vif is about to be deleted. To be able to do that, all open patches need to be abandoned. Please cherry pick the patch to unmaintained/yoga if you want to further work on this patch.

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Elod Illes <email address hidden>" on branch: stable/wallaby
Review: https://review.opendev.org/c/openstack/os-vif/+/886778
Reason: stable/wallaby branch of openstack/os-vif is about to be deleted. To be able to do that, all open patches need to be abandoned. Please cherry pick the patch to unmaintained/wallaby if you want to further work on this patch.

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Elod Illes <email address hidden>" on branch: stable/xena
Review: https://review.opendev.org/c/openstack/os-vif/+/886716
Reason: stable/xena branch of openstack/os-vif is about to be deleted. To be able to do that, all open patches need to be abandoned. Please cherry pick the patch to unmaintained/xena if you want to further work on this patch.