Hi, Han. I'm still trying to come up with a mechanism I like, but in the meantime, can you try applying this patch and re-running your trace? This should provide a better indication of what's causing that field to be un-wildcarded.
Thanks, --Justin
new_wildcards.diff
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> On Sep 6, 2018, at 7:07 PM, Han Zhou <[email protected]> wrote: > > As mentioned in today's OVN meeting, I observed a problem regarding megaflow > effectiveness. Now I have more details but really need help from folks here. > Originally I thought it is due to the way OVN is programming the flows, but > now I even wonder it could be a problem in OVS (or my misunderstanding about > OVS). > > In this OVN setup I observed unreasonably high flow-miss rate on chassis > nodes, especially the gateway nodes. Then with ovs-dpctl dump-flows I saw > many udp flows installed for same match conditions expect the udp dst port, > i.e. only the udp(dst=xxxxx) part is different. This would cause UDP sessions > latency, since in this scenario most of those udp packets are short lived > flows and all processed in slowpath. However I didn't see such problem for > TCP. > > At first I suspected the dhcp port related flows in port-security stage could > cause the megaflow always have the udp port in the match condition, but it > turns out this is not the case because the dhcp flows matches the specific > broadcast IP and 0.0.0.0 only. I confirmed this by debugging on the gateway > node - there is no udp related flows installed at all in gateway node > userspace because port-security is not relevant for gateway node, and there > is no flow with tp_dst in match condition either. I verified by ovs-ofctl > dump-flows br-int | grep udp. i.e., below commands returns no result: > > # ovs-ofctl dump-flows br-int | grep udp > # ovs-ofctl dump-flows br-int | grep tp_dst > # ovs-ofctl dump-flows br-int | grep tp_src > > So could anyone explain what could cause so many megaflows installed in > datapath, each with specific udp dst port? > > Please find the example flows and trace, ovn-detrace output here: > https://gist.github.com/hzhou8/763e18c209aab40e7f3d6bd0690cea6f > > Thanks, > Han > > _______________________________________________ > discuss mailing list > [email protected] > https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
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