Re: [E1000-devel] Issue with GRO on IGB in Linux Router

[Scott S. <ssi...@si...>]

I would like to add a few things to my post:

First, I noticed this issue both when routing through the box or when
running an iperf with the tcp endpoint as the box itself.

Second, It seems that GRO was not an option/enabled (at least as far as I
can tell from ethtool -k) until driver 2.1.1, I have other boxes running
2.0.6 and do not see any GRO in the ethtool -k output. I looked back through
the release notes and didn't see anything about gro at all.

Thanks,
Scott Silverman

On Wed, Dec 23, 2009 at 1:08 PM, Scott Silverman <
ssi...@si...> wrote:

> I have experienced an issue that I believe lies with the GRO implementation
> in IGB 2.1.1.
>
> The problem I see is that when GRO is enabled, TCP connections through the
> router are limited to approximately 300-500 kbps. If I disable GRO, I can
> get the full expected throughput. Regardless of offload settings, UDP
> connections are able to utilize the full expected bandwidth.
>
> I initially suspected that a firewall, or trafficshaping, issue was causing
> this problem, but ruled those out. Later, dumps of traffic turned up the
> fact that the machine believed it was receiving oversized (~2000 byte)
> packets, which led us to investigate the offload settings.
>
> The router device in question is based on the Intel 5520 Chipset, and is
> running kernel 2.6.29.6 (from kernel.org). I am using the igb 2.1.1 driver
> from intel.com. The card in question is an Intel Gigabit ET Quad Port,
> though I also see the issue on a LOM 82576 based NIC in the same box.
>
> Please let me know if there are any other details or information that might
> be of use in tracking this down.
>
> Thanks,
> Scott Silverman
>
>