[ovs-dev] [PATCH] VxLAN-gpe implementation

Hannes Frederic Sowa hannes at redhat.com
Thu Jun 9 10:57:21 UTC 2016


On 09.06.2016 04:33, Alexander Duyck wrote:
> On Wed, Jun 8, 2016 at 3:20 PM, Hannes Frederic Sowa <hannes at redhat.com> wrote:
>> The remaining problem regarding offloads would be, that we by default
>> get into the situation that without the special offloading rule the
>> vxlan stream will only be processed on one single core, as we tell
>> network cards not to hash the udp ports into rxhash, which hurts a lot
>> in case of vxlan, where we bias the flow identification on the source
>> port without offloading available.
> 
> Most NICs offer the option of hashing on UDP ports.  In the case of
> the Intel NICs I know you can turn on UDP port hashing by using
> ethtool and setting UDP hasing to be enabled via "ethtool -N <iface>
> udp4 sdfn".  You can do the same thing using "udp6" for IPv6 based
> tunnels.  That is usually enough to cover all the bases and the fact
> is not too many people are passing fragmented UDP traffic and as long
> as that is the case enabling UDP hashing isn't too big of a deal.

True, I am wondering how safe it is given the reordering effects it has
on UDP and thus other non vxlan management protocols on the hypervisors.

At that time, when UDP port hashing was disabled, the message was pretty
clear by upstream and I don't think for the default case anything should
change here.

Are the port hashing features also global or tweakable per VF?

Thanks,
Hannes





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