On 16/2/2022 6:38 pm, Daniel Alvarez wrote:
On 16 Feb 2022, at 06:02, Jake Yip via discuss <[email protected]>
wrote:
Hi all,
We are running VMs on OpenStack with OVN. We have an issue with performance,
tested using iperf3 with TCP. We get like ~300Kbits in the problematic
scenario, when normal traffic is around 1Gbps. Some observations are:
* Only TCP is affected, not UDP iperf3 tests
* It only happens between some nodes, not others
* In only happens in one direction in some cases
We've looked into this and found that the poor performance may be due to
retransmission / congestion. Looking deeper, there seems to be some interesting
behaviour with fragmentation? / reassembly
Our architecture is like this:
VM23 - [TAP23 - BOND23] -- (internet) -- [BOND21 - TAP21] - VM21
VMs are on hypervisors, on the hypervisor the tap devices egress out bonds. The
We have done tcpdumps from VM23 , VM21, BOND21 and TAP21.
What we have found is that a PSH,ACK packet from VM23 is re-written into a ACK
packet when it gets to the bond.
When it gets to the other side, these packets doesn't seem to be reassembled
properly to be passed onto the tap into VM21.
We would like to know if this behaviour (rewriting a PSH,ACK into separate ACK
packet) is a normal behaviour of OVS/OVN? Is there any other reason why there
are so many retransmissions?
I'm not sure if this is an OVN or OVS issue, apologies if this is not the right
list. I'm also not sure if I'm debugging this issue correctly. Any help will be
welcome!
Which NICs are you using?
Is this Geneve traffic? over VLAN?
If so, may you re run your tests by disabling the VLAN tx offload in both
hypervisors (w/ ethtool)?
Cheers,
Daniel
Thanks!
We tried disabling VLAN tx offload on the hypervisors, no difference.
Also tried turning off a few offloading, no difference too.
Interestingly, same VM hypervisor only has problems to some VMs, not
others. If it was a offload issue, will that affect traffic to all VMs
equally?
I'm not sure if it is related to HW or SW, it is all very peculiar.
Regards,
Jake
_______________________________________________
discuss mailing list
[email protected]
https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
