lkml.org 
[lkml]   [2008]   [Feb]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: TG3 network data corruption regression 2.6.24/2.6.23.4
Michael Chan wrote:
> 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.
>
>
>
Confirmed. With a 100 MB read/write test, netstat -s shows 75 bad
segments received, and performance in the one direction is about 5
MB/s. When I switch to the SysKonnect NIC, netstat -s shows 0 bad
segments received, and performance is 115 MB/s. So that solves that
mystery - there is still data corruption, but the software-computed TCP
checksum causes the bad packets to be retransmitted rather than being
passed on to the application.

Tony



\
 
 \ /
  Last update: 2008-02-20 16:03    [from the cache]
©2003-2011 Jasper Spaans