Regards _Sugesh
> -----Original Message----- > From: Zoltán Balogh [mailto:[email protected]] > Sent: Friday, May 26, 2017 3:01 PM > To: Joe Stringer <[email protected]> > Cc: Chandran, Sugesh <[email protected]>; Andy Zhou > <[email protected]>; William Tu <[email protected]>; > [email protected]; ovs dev <[email protected]>; Ben Pfaff > <[email protected]>; Jan Scheurich <[email protected]>; Gray, Mark D > <[email protected]> > Subject: RE: [ovs-dev] [PATCH v5] tunneling: Avoid recirculation on datapath > by computing the recirculate actions at translate time. > > > Hi Joe, > > > Backing up a bit for context, the stats attribution goes roughly like this: > > * First upcall, handler thread calls through the translate code with a > > packet. The resubmit_stats are derived from that packet. This goes > > through xlate_actions(). > > * First dump of flow from revalidator thread fetches the flow and runs > > the same xlate_actions() with whatever stats it has (may be zero). > > This time, whenever stats attribution or side effects occur, an > > xlate_cache entry is generated. > > * Second and subsequent dumps of flows fetches the flow and shortcuts > > the xlate_actions() by using the xlate_cache instead - ie a call to > > xlate_push_stats(). > > > > So, in the same place where the resubmit_stats is manipulated, you > > would also need to generate a new XC entry which would manipulate the > > stats - this would be a 'side-effect'. I'd imagine that prior to the > > full output translation there would be a XC_TRUNCATE(truncated_size) > > then afterwards there would be an XC_TRUNCATE_RESET(). Or it could be > > just XC_SET_SIZE(...) where 0 is reset and non-zero is a truncate > > size. In the implementation/execution in xlate_push_stats() when > > performing XC_TRUNCATE you would need to store the original push_stats > > size somewhere, then calculate a new 'n_bytes' based on the number of > > packets and existing bytes*. For XC_TRUNCATE_RESET(), it would restore > > the original push_stats size. > > Thank you for the explanation. > > > * Hmm, I'm not sure the calculation will be 100% here. Let's say there > > were 3 packets hit the flow, 50B, 200B, 300B. If output(max_len=100) > > was executed, then we don't know how many of the packets were > > truncated. The maximum number of bytes that could be transmitted is > > 300, but the actual number was 250. We could divide the n_bytes by > > n_packets, subtract the max_len and then multiply back up by the > > number of packets, which works for this case assuming floating point > > arithmetic but is slightly off if using integer math.. > > I don't think, that would be the proper way of calculating n_bytes. Let's say > we have 3 packets with 50B, 200B, 200B and max_len=100. The output should > be 50 + 100 + 100 = 250B. > Following the instructions above we will get > [(50 + 200 + 200) / 3 - 100 ] * 3 = [450 / 3 - 100 ] * 3 = 50 * 3 = 150B > > Any other idea how to calculate the truncated size with xlate cache? > Or maybe I did not understand your calculation. [Sugesh] Since we have this issue with the trunc action, How about limit the combine action only for those tunnels that don’t have any post trunc action. If there is a trunc action, Create two separate rules normally as now. Is there any other action that would be considered as exception like this? > > There is one more thing to be taken into consideration. By adding a tunnel > header, the size of packets increases as well. But that's a constant value for > each packet, easier to calculate with it. > > Best regards, > Zoltan _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
