[ofa-general] mlx4 second port lro issue

[Barry Mavin]

Is LRO on by default? If not how can we enable it?

---
Regards
Barry Mavin
Recital Corporation



> From: Boris Shpolyansky <boris at mellanox.com>
> Date: Thu, 10 Sep 2009 19:31:35 -0700
> To: Shirley Ma <mashirle at us.ibm.com>
> Cc: Roland Dreier <rdreier at cisco.com>, <general at lists.openfabrics.org>
> Subject: RE: [ofa-general] mlx4 second port lro issue
> 
> 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:mashirle at us.ibm.com]
> Sent: Thursday, September 10, 2009 7:08 PM
> To: Boris Shpolyansky
> Cc: Roland Dreier; general at 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
> 
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