NET.performance issue: MTU for qr-*, qg-*, tap-* interfaces in network namespaces of hdcp and l3 agents should be adjusted to external and private MTU

[Sergey Vasilenko]

DHCP and L3 agents create qr-*, qg-*, tap-* interfaces with default (1500) MTU.
After increasing MTU inside instances, instance will emit network packets up to 9000 payload size. If that packets has ho DF flags we will have segmentation and network performance (VM to outside world) degradation. Packets with DF flags will be dropped.
Incoming (from outside world to, for example, floating IP) traffic will be emitted from namespace to VM as packets with up to 1500 payload size and may me segmented to. In any FLOATING-IP cases increasing MTU to 9000 on VM useless.

Neutron has 'network_device_mtu' option (in agent configuration file) for configure MTU.

We should use this option for adjusting MTU on agents interfaces.

[Bartłomiej Piotrowski (bpiotrowski)]

Sergey told me that Sergey Kolekonov is implementing a function for getting base (phys) interface for any endpoint. After that it'll be sensible to deal with this issue.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/182979

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/183049

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/183049
Committed: https://git.openstack.org/cgit/stackforge/fuel-library/commit/?id=9c05cbf2c7261983110510902f3b58eff74ad59e
Submitter: Jenkins
Branch: master

commit 9c05cbf2c7261983110510902f3b58eff74ad59e
Author: Bartłomiej Piotrowski <email address hidden>
Date: Thu May 14 15:50:44 2015 +0200

    Set appropriate MTU for Neutron agents

    + move MTU size calculation to level UP

    Change-Id: I19726d635a16cfa30d8df099041cd76fb88a2de0
    Closes-Bug: 1453425

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/182979
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=3f1ba76e357c780d617f83dd41590766a41d7fed
Submitter: Jenkins
Branch: master

commit 3f1ba76e357c780d617f83dd41590766a41d7fed
Author: Igor Kalnitsky <email address hidden>
Date: Thu May 14 11:51:39 2015 +0300

    Set mtu=65000 on patchcord br-floating/br-ex

    We have to increase mtu for br-floating/br-ex patchcord because
    otherwise we will have performance degradation if some VM use
    non-default mtu.

    Related-Bug: #1453425

    Change-Id: I3b28c01d112b5951c62e35eeabe8f2f4fd67a475
    Signed-off-by: Igor Kalnitsky <email address hidden>

[Vitaly Sedelnik (vsedelnik)]

Won't Fix for 6.0-updates as there is no delivery channel for Fuel fixes in 6.0 updates