Neutron, openvswitch jumbo packets

[James Page]

Hi Ed

On Sat, 7 May 2016 at 10:30 ed bond <celpa.firl at gmail.com> wrote:

> Anyone have experience with the charms to be able to set the MTU to jumbo
> packets?
>
> Right now in testing to see if it would work we had to do this:
>
> for i in `ip a | grep mtu| egrep -ve
> "eth0|eth1|eth2|eth3|bond0|lo|juju-br0" | awk '{print $2}' | awk -F:
> '{print $1}'`; do ip link set ${i} mtu 8900; done
>
> We were able to get 6.5 Gigabit/s throughput with enabling jumbo packets.
>

>
> *ubuntu at 3-885bd897-3655-42ab-b0b9-a97b31826f88*:*~*$ sudo ip link set dev
> ens3 mtu 8000
> *ubuntu at 3-885bd897-3655-42ab-b0b9-a97b31826f88*:*~*$ sudo iperf -c
> 192.168.10.116 -i1 -t 10 -m
> …
> [  3] local 192.168.10.115 port 33920 connected with 192.168.10.116 port
> 5001
> [ ID] Interval       Transfer     Bandwidth
> [  3]  0.0- 1.0 sec   845 MBytes  7.09 Gbits/sec
> [  3]  1.0- 2.0 sec   781 MBytes  6.55 Gbits/sec
> [  3]  2.0- 3.0 sec   762 MBytes  6.40 Gbits/sec
> [  3]  3.0- 4.0 sec   758 MBytes  6.36 Gbits/sec
>
> Any openstack charmers have some insight?
>

Jumbo frames are absolutely recommended for compute and gateway nodes;  you
only really need to set the MTU on the base network devices (eth0 for
example) and any other veth's connected to the bridges - Juju has a setting
todo this in older releases and I think it might actually do it
automatically if the MTU is set high on the base network interface (but I
might be wrong).

With regards to setting the MTU automatically, MAAS allows you to specify
the MTU for subnets/fabrics, and will automatically set the MTU on
configured (and unconfigured) network interfaces based on server
connectivity to underlying network fabrics which is super useful and nicely
automatic - for example:

  maas mymass vlan update 0 103 mtu=9000

would update vlan 103 to have a default mtu of 9000 - check out the full
details on "vlan update" for how to target individual VLAN's.

OpenStack Mitaka also has the ability to manage the MTU on overlay networks
natively (on the assumption you're doing jumbo frames under the hood) - but
I've not poked at that in any level of anger just yet.

Cheers

James
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