Subject: Re: TG3 network data corruption regression 2.6.24/2.6.23.4

From: "Michael Chan" <[email-masked]>
Date: Tue, 19 Feb 2008 15:52:43 -0800

On Tue, 2008-02-19 at 17:14 -0500, Tony Battersby wrote:

> 
> Update: when I revert Herbert's patch in addition to applying your
> patch, the iSCSI performance goes back up to 115 MB/s again in both
> directions.  So it looks like turning off SG for TX didn't itself cause
> the performance drop, but rather that the performance drop is just
> another manifestation of whatever bug is causing the data corruption.
> 
> I do not regularly use wireshark or look at network packet dumps, so I
> am not really sure what to look for.  Given the above information, do
> you still believe that there is value in examining the packet dump?
> 

Can you confirm whether you're getting TCP checksum errors on the other
side that is receiving packets from the 5701?  You can just check
statistics using netstat -s.  I suspect that after we turn off SG,
checksum is no longer offloaded and we are getting lots of TCP checksum
errors instead that are slowing the performance.