Hi,team.
In OVS-DPDK scenarios, using ovs-tcpdump for packet capture can
significantly impact forwarding performance due to the packet processing
between user space and kernel space.
This impact is especially noticeable when there is high traffic or when
multiple capture ports are started, causing the performance to degrade
drastically.
Therefore, the question is whether we have considered improving the packet
capture capability of ovs-tcpdump in OVS-DPDK scenarios. Based on my analysis,
I believe replacing the default ovs-tcpdump mirror port with the DPDK
virtio-user interface would greatly enhance processing performance.
https://doc.dpdk.org/guides-24.11/howto/virtio_user_as_exception_path.html
Command to create a virtio-user port on an OVS-DPDK bridge：
ovs-vsctl --may-exist add-port br-tun veth1 -- set interface veth1 type=dpdk --
set interface veth1
options:dpdk-devargs="vdev:virtio_user0,path=/dev/vhost-net,iface=veth1"
After creation, the corresponding interface veth1 is bound to PMD：
[root@compute0-dpdk /]# ovs-appctl dpif-netdev/pmd-rxq-show
pmd thread numa_id 1 core_id 21:
isolated : false
port: tun_port_p0 queue-id: 0 (enabled) pmd usage: 0 %
port: vh-userclient-e5281ddf-c8 queue-id: 0 (enabled) pmd usage: 0 %
overhead: 0 %
pmd thread numa_id 1 core_id 22:
isolated : false
port: tun_port_p0 queue-id: 1 (enabled) pmd usage: 0 %
port: veth1 queue-id: 0 (enabled) pmd usage: 0 %
overhead: 0 %
pmd thread numa_id 1 core_id 23:
isolated : false
port: tun_port_p1 queue-id: 0 (enabled) pmd usage: 0 %
overhead: 0 %
pmd thread numa_id 1 core_id 24:
isolated : false
port: tun_port_p1 queue-id: 1 (enabled) pmd usage: 0 %
overhead: 0 %
And the corresponding veth1 kernel interface can be seen in the kernel：
[root@compute0-dpdk /]# ip ad|grep veth1
700: veth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default
qlen 1000
So, we only need to redirect the mirrored traffic to the virtio-user port,
which significantly improves performance compared to the default kernel-space
mirror port.
Jun Wang
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