Subject: Re: forcedeth driver hangs under heavy load

From: stephen mulcahy <[email-masked]>
Date: Tue, 13 Apr 2010 16:00:25 +0100

stephen mulcahy wrote:
>> Now some brave fouls to check the 6410 lines of this driver ? ;)
>>
>> Question of the day : Why TSO is broken in forcedeth ?
>> Is it generically broken or is it broken for specific NICS ?
>>
> 
> Actually, it is only when tx-checksumming is turned off that the problem 
>  doesn't occur (so I'm not sure TSO is the problem).
> 
> Additionally, a google also turns up this existing Debian bug 
> http://bugs.debian.org/506419 which seems to be related.

As mentioned in the original Debian bug - I can reproduce this by 
running Hadoop[1] TeraSort[2] but I haven't identified a simpler 
reproducer. I tried to recreate this with iperf and ping -f but neither 
helped - it may be that the problem only occurs when systems are passing 
large amounts of traffic and have very high cpu utilisation (when 
running the Hadoop TeraSort all 8 cores run at 70-100% utilisation as 
measure with htop - I plan to instrument the nodes with something like 
Zabbix or Ganglia but it hasn't happened yet).

-stephen

[1] http://hadoop.apache.org/
[2] 
http://hadoop.apache.org/common/docs/current/api/org/apache/hadoop/examples/terasort/package-summary.html