[ovs-discuss] Openstack VM to VM Communication so slow when using OVN+GENEVE

[Popoi Zen]

Thanks Dan for your answer. In my case, it seems Geneve port (6081) didn't
work (don't know why), so I change Geneve port to 6082 for temporary
workaround.

On Mon, Sep 21, 2020 at 4:31 PM Dan Sneddon <dsneddon at redhat.com> wrote:

> I have seen this behavior many times when the MTU is not large enough at
> some point in the tunnel path for the encapsulated data plus the Geneve
> header plus the VLAN tag.
>
> You can either decrease the MTU on the overlay (encapsulated) network, or
> increase the MTU at all hops on the underlay network to compensate.
>
> Neutron has a parameter in the ml2_conf.ini file in the “[ml2]” section
> named “path_mtu” which should match the lowest MTU of any hop in the path
> between the tunnel endpoints. The correct MTU will be calculated and
> advertised via DHCP if the “asvertise_mtu” parameter is true (default) in
> the neutron.conf file.
>
> This value may be set separately from the “global_physnet_mtu” in
> neutron.conf which will set a default MTU for provider networks, as well as
> the “physical_network_mtus” map in the “[ml2]” section of the ml2_conf.ini
> which sets specific physical network MTUs.
>
> For more information, see:
> https://docs.openstack.org/newton/networking-guide/config-mtu.html
>
>
> -Dan
>
> On Mon, Sep 21, 2020 at 2:16 AM Popoi Zen <alterriu at gmail.com> wrote:
>
>> I have Openstack cluster with following environments:
>> * 3 Controller+ 2 Compute
>> * Interfaces example:
>> bond0: provider network mapped to here using vlan
>> bond0.2602 at bond0: interface for overlay
>> br-tun:  172.28.237.13/24 --> bond0.2602 attached to here --> this is
>> overlay endpoint for Geneve.
>>
>> On each compute node, I exec this command:
>>
>> ```
>> ovs-vsctl add-br br-tun
>> ovs-vsctl add-port br-tun bond0.2602
>> ip addr delete 172.28.237.13/24 dev bond0.2602
>> ip addr add 172.28.237.13/24 dev br-tun
>> sudo ip link set br-tun up
>> ```
>>
>> I create 2 VM ubuntu0(on compute2) and ubuntu1 (on compute3) then testing
>> SSH between VM using private IP. It took times ~1 minutes until login
>> prompt appear.
>>
>> It seams normal when pinging:
>> ```
>> ubuntu at ubuntu1:~$ ping ubuntu0
>> PING ubuntu0 (192.168.5.187) 56(84) bytes of data.
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=1 ttl=64 time=1.13 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=2 ttl=64 time=0.968 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=3 ttl=64 time=0.911 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=4 ttl=64 time=0.567 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=5 ttl=64 time=0.645 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=6 ttl=64 time=0.602 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=7 ttl=64 time=0.635 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=8 ttl=64 time=0.380 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=9 ttl=64 time=0.640 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=10 ttl=64 time=0.523 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=11 ttl=64 time=0.907 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=12 ttl=64 time=0.725 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=13 ttl=64 time=0.574 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=14 ttl=64 time=0.724 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=15 ttl=64 time=1.16 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=16 ttl=64 time=0.947 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=17 ttl=64 time=0.457 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=18 ttl=64 time=0.428 ms
>> 64 bytes from ubuntu0 (192.168.5.187): icmp_seq=19 ttl=64 time=1.08 ms
>> ```
>>
>> Could someone give me some hint where to start to debug or where is the
>> issue?
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>>
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>>
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>>
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>>
>> --
> Dan Sneddon         |  Senior Principal Software Engineer
> dsneddon at redhat.com |  redhat.com/cloud
> dsneddon:irc        |  @dxs:twitter
>
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