[ovs-dev] How can we improve veth and tap performance in OVS DPDK?

[Ilya Maximets]

On 29.07.2019 19:07, Ilya Maximets wrote:
>> Hi, all
>> We’re trying OVS DPDK in openstack cloud, but a big warn makes us hesitate.
>> Floating IP and qrouter use tap interfaces which are attached into br-int,
>> SNAT also should use similar way, so OVS DPDK will impact on VM network
>> performance significantly, I believe many cloud providers have deployed OVS
>> DPDK, my questions are:
>>
>> 1.       Do we have some known ways to improve this?
> 
> As RedHat OSP guide suggests, you could use any SDN controller (like OpenDayLight)
> or, alternatively, you could use OVN as a network provider for OpenStack.
> This way all the required functionality will be handled by the OpenFlow rules
> inside OVS without necessity to send traffic over veths and taps to Linux Kernel.
> 
>> 2.       Is there any existing effort for this? Veth in kubernetes should
>> have the same performance issue in OVS DPDK case.
> 
> It makes no sense right now to run OVS-DPDK on veth pairs in Kubernetes.
> The only benefit from OVS-DPDK in K8s might be from using virtio-vhost-user

I meant virtio-user ports.

> ports instead of veths for container networking. But this is not implemented.
> Running DPDK apps inside K8s containers has a lot of unresolved issues right now.
> 
> One approach that could improve performance of veths and taps in the future is
> using AF_XDP sockets which are supported in OVS now. But AF_XDP doesn't work
> properly for virtual interfaces (veths, taps) yet due to issues in Linux Kernel.
> 
>>
>> I also found a very weird issue. I added two veth pairs into ovs bridge and
>> ovs DPDK bridge, for ovs case, iperf3 can work well, but it can’t for OVS
>> DPDK case, what’s wrong.
> 
> This is exactly same issue as we already discussed previously. Disable tx offloading
> on veth pairs and everything will work.
> 
> Best regards, Ilya Maximets.
> 
>