Bug in igb driver

[Michael]

Hello,

we encountered problems using igb driver on a Supermicro dual quad-core
system (X7DWU).
It features an Intel Gigabit dual port controller (82575).

The IP forwarding performance was extremely bad (5 kb/s up to 50 kb/s)
until we disabled
Large Receive Offloading in /etc/sysctl.conf:
dev.igb.0.enable_lro=0
dev.igb.1.enable_lro=0

(changing it using ifconfig -lro and down/up the interfaces didn't help).

With the systctl values set as shown above, we get the expected
performance ob 50-60 MB/s.
We tested this on 7.1-RELEASE, 7.2-RELEASE and 7-STABLE. Right now we're
installing
8-CURRENT on the machine to see if it makes a difference.

It think it would be worthwhile to list this issue in the 7.2 release
errata section (that would've
saved us a significant amount of time :).

Cheers
Michael