[Beowulf] tcp error: Need ideas!
landman at scalableinformatics.com
Wed Jan 21 18:23:17 EST 2009
Gerry Creager wrote:
> History/background/description of the cluster
> * 126 node Dell 1950 cluster with dual-quad core Xeons
> * HP 5412zl switch for gigabit cluster backplane and 10GBE interconnect
> to selected services (file server, etc)
> * Gigabit interconnect
> * Hand compiled 2.6.26 kernel
> * bnx2 module loaded for the Broadcom onboard nics
> * Switch, compute nodes, head node set to 9000 byte MTU
We have had *lots* of problems with Broadcom nics and jumbo frames.
From 2.6.9 timeframe onwards.
> We're seeing the following error in WRF compiled with openMPI and the
> PGI 7.2 compiler:
> mca_btl_tcp_frag_send:writev failed with errno=104
> While all nodes were accessible prior to the run and returned
> appropriate "stuff" when queried with, eg., ssh and a command, two nodes
> now return something like this:
> [gerry at brazos SCOOP12km]$ ssh c0522
> Received disconnect from 192.168.200.154: 2: Bad packet length 808464432.
Hmmm... sounds like a link tried re-negotiating. Can you get on via
root at lightning:~# ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
Advertised auto-negotiation: Yes
Port: Twisted Pair
Supports Wake-on: g
Current message level: 0x000000ff (255)
Link detected: yes
You might want to
ethtool eth0 autoneg off
to force it not to renegotiate its speed. Also, look at
root at lightning:~# ethtool -g eth0
Ring parameters for eth0:
RX Mini: 0
RX Jumbo: 0
Current hardware settings:
RX Mini: 0
RX Jumbo: 0
See if you can do something like
ethtool -G eth0 rx-jumbo 100
if you have zero jumbo ring rx entries.
> I'm stumped and looking for causes and solutions. Yeah, the WRF as
> compiled did run before the change to Jumbos.
> Do I reduce the size of the frames to something smaller, like 8800
> bytes? 7500? 1500?
In the past I had heard that jumbo frames may work on Broadcom NICs
around 6000 byte length. We haven't tried this in a while ... YMMV.
> I'm not completely out of ideas but stumped.
> Thanks, gerry
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web : http://www.scalableinformatics.com
phone: +1 734 786 8423 x121
fax : +1 866 888 3112
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