[ovs-discuss] [ovs-dev] DPDK: How to send packets from one OVS bridge to another OVS bridge while running in the same user space ?

Jan Scheurich jan.scheurich at ericsson.com
Wed Feb 14 08:11:31 UTC 2018

Hi Kapil,

I am afraid there is no really efficient way today to connect a user-space (netdev-dpdk) datapath in OVS to kernel interfaces (such as internal/tap ports or veth pairs) today. Communication works but packet I/O is very slow compared to DPDK interfaces (both ethernet and vhostuser). The PMD threads polling the DPDK interfaces are heavily slowed down when sending packets to kernel ports and in the other direction all kernel interfaces are polled by the main ovs-vswitchd thread.

If your other bridge also uses DPDK in user space, you can try with DPDK ring ports as interface between the two bridges. DPDK ring ports should be supported in OVS.

Another almost as efficient solution for sending packets from the OVS DPDK datapath to another DPDK vSwitch would be to run the other vSwitch in a VM and connect it to OVS-DPDK on the host through a vhostuser port. The DPDK vSwitch in the VM would then use the virtio PMD, I expect this to be supported by all DPDK vSwitches.

BR, Jan

From: Kapil A [mailto:kapil20084 at gmail.com]
Sent: Wednesday, 14 February, 2018 03:47
To: Jan Scheurich <jan.scheurich at ericsson.com>
Cc: discuss at openvswitch.org; dev at openvswitch.org
Subject: Re: [ovs-dev] DPDK: How to send packets from one OVS bridge to another OVS bridge while running in the same user space ?

Hi Jan,

Thanks for the clarification. I also came across patch port as the best option between ovs Bridges. But, is it possible to use patch ports to an external OpenFlow bridge? Like one bridge is OVS, other is Lagopus bridge or LINC bridge? For my use case, I want to send packets from OVS Bridge to another OpenFlow bridge(like a loopback port) as OVS doesn't support the functionality I am looking for.

On Tue, Feb 13, 2018, 21:22 Jan Scheurich <jan.scheurich at ericsson.com<mailto:jan.scheurich at ericsson.com>> wrote:
Hi Kapil,

This is what patch ports are for. They are only traversed for the first packet of a flow in the slow path. The resulting datapath flow entry collapses the processing in both bridges into a single megaflow. So there is no performance overhead compared to having a single bridge.

Regards, Jan

> -----Original Message-----
> From: ovs-dev-bounces at openvswitch.org<mailto:ovs-dev-bounces at openvswitch.org> [mailto:ovs-dev-bounces at openvswitch.org<mailto:ovs-dev-bounces at openvswitch.org>] On Behalf Of Kapil A
> Sent: Tuesday, 13 February, 2018 16:44
> To: discuss at openvswitch.org<mailto:discuss at openvswitch.org>; dev at openvswitch.org<mailto:dev at openvswitch.org>
> Subject: [ovs-dev] DPDK: How to send packets from one OVS bridge to another OVS bridge while running in the same user space ?
> Hello,
> In my setup, i have two DPDK ports, where dpdk0 is part of br0 and and
> dpdk1 is part of br1. How can i send packets from br0 to br1 in an
> efficient way within userspace with good performance?
> I came across, veth pair as one option, but i couldn't find if it will
> provide good performance in userspace while running in dpdk mode ?
> My query might sound odd, but i have a use case where i need to send the
> packets across bridges within the same userspace, so appreciate some help
> on this.
> Regards
> Kapil
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