Shirley, Are you referring to actual Ethernet frame size or to TCP message size? If the port MTU set to 1500 it will reject Ethernet frames larger than this size, this has nothing to do with the LRO. LRO is a TCP offload that improves CPU utilization on the TCP receiver by combining multiple packets belonging to the same TCP stream to a single buffer and transferring it to the TCP stack as a single large packet.
Boris Shpolyansky Sr. Member of Technical Staff, Applications Mellanox Technologies Inc. 350 Oakmead Parkway, Suite 100 Sunnyvale, CA 94085 Tel.: (408) 916 0014 Fax: (408) 585 0314 Cell: (408) 834 9365 www.mellanox.com -----Original Message----- From: Shirley Ma [mailto:mashi...@us.ibm.com] Sent: Thursday, September 10, 2009 7:08 PM To: Boris Shpolyansky Cc: Roland Dreier; general@lists.openfabrics.org Subject: RE: [ofa-general] mlx4 second port lro issue Hello Boris, On Thu, 2009-09-10 at 14:16 -0700, Boris Shpolyansky wrote: > Dumb question: what was the MTU setting of the eth interface > associated > with port 2? Dropping jumbo frames has nothing to do with LRO - it is > plain layer 2 functionality. ifconfig shows both port1 and port2 mtu are 1500. port 2 does't drop jumbo frames. The problem is the LRO is on for both interfaces so the interface will get large packet (packet size 1848). port1 can receive it and process it, but not port2. If I disables lro by reloading module with num_lro=0, then it will get small packet, and port2 works fine. My question here is why port1 can work well for lro but not port2. Thanks Shirley _______________________________________________ general mailing list general@lists.openfabrics.org http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
