[Beowulf] Full-duplex performance problems with Intel Gigabit Ethernet cards?

[Bogdan Costescu]

On Thu, 4 Aug 2005, Felix Rauch Valenti wrote:

> Are there any known performance problems with Intel 82541GI/PI or
> 82547GI Gigabit Ethernet cards?

The 82541GI/PI cards are normally connected to a 32-bit, 33MHz PCI
bus, which limits the total transfer speed; 2 x 50Mbyte/s is
reasonably close to the maximum.

On quick tests made here with 2 nodes each with a single CPU P4 3.2GHz
and a 82541GI/PI card, I get about 90Mbyte/s single flow versus about
2x48Mbyte/s when transferring simultaneously in both directions.  
However the double flow is also associated with a high interrupt rate
(44K/s) and context switches (59K/s), which might also act as limits.
(tests done with nc < /dev/zero and nc > /dev/null, no Jumbo frames; 
measurements with dstat http://dag.wieers.com/home-made/dstat/)

-- 
Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De