jumping in the conversation: last year when Gaetano and I worked on this code, the main loop had multiple performance issues, including a) rebuilding from scratch the list of file descriptors on each iteration, b) ignoring the response from select() and firing all handlers (and perhaps looking at timeouts ?) on return, and c) processing only one packet per iteration.
Our feeling at the time was that: - a patch that fixed #a and #b in the main loop would have a much lower chance of being accepted; - user-space forwarding was not a priority fo the project given the existence of the in-kernel module for linux (though we may disagree on this, given that together with netmap this makes it possible to get much better throughput); - we were unsure how much #a could be simplified in the main loop, whereas splitting the event loop in two makes the handling of the forwarding path a lot more efficient; - also having a separate forwarding thread probably would save some latency in the forwarding when the main thread is busy with the control path. and these are the reasons why we went for a separate thread. Also, we were not completely sure on how to address #a in the main loop, whereas this is somewhat simpler in the secondary thread which only has to deal with the dp_netdevs list. An option to move forward could be to make the entire patch conditional (it almost is this way now, but we can certainly work on making the patch less intrusive and clearly mark the conditional block) and possibly default to off, so that people not comfortable with the threaded extension will not have to deal with it. In the meantime you can perhaps try to import some of the performance enhancements in the main code (though again i am not sure how efficiently high-speed packet-IO events can coexist with the control-plane related one. cheers luigi -- -----------------------------------------+------------------------------- Prof. Luigi RIZZO, ri...@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL +39-050-2211611 . via Diotisalvi 2 Mobile +39-338-6809875 . 56122 PISA (Italy) -----------------------------------------+------------------------------- _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
