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network speed extremly slowed down

To: netdev@xxxxxxxxxxx
Subject: network speed extremly slowed down
From: Bernd Schubert <bernd.schubert@xxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 14 Mar 2005 17:45:06 +0100
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Hi,

until one hour ago I thought this bug affects only 3com 3c509B cards. Now we 
go on switching more and more systems from 2.4.X to 2.6.X and it seems that 
many cards work much slower with 2.6.X

with 2.4.27:
=========
bernd@pc-brenn bernd>nttcp -T hamilton2
     Bytes  Real s   CPU s Real-MBit/s  CPU-MBit/s   Calls  Real-C/s   CPU-C/s
l  8388608    0.72    0.02     92.7710   3355.4432    2048   2831.15  102400.0
1  8388608    0.73    0.04     92.0581   1864.3941    5783   7932.96  160661.2

with 2.6.11.3:
==========

bernd@pc-brenn bernd>nttcp -T hamilton2
     Bytes  Real s   CPU s Real-MBit/s  CPU-MBit/s   Calls  Real-C/s   CPU-C/s
l  8388608    3.29    3.28     20.3957     20.4569    2048    622.43     624.3
1  8388608    3.29    0.04     20.3923   1637.0411    6143   1866.67  149851.2


Cards that show this behaviour:
=======================
Yukon Gigabit Ethernet 10/100/1000Base-T Adapter (sk98lin)
3Com PCI 3c905B Cyclone 100baseTx a
eth0: VIA VT6102 Rhine-II 

Cards that work fine with 2.4.X and 2.6.X:
==============================
3Com PCI 3c905C Tornado


The drivers always claim they are using full duplex, here e.g.:

eth0: network connection up using port A
    speed:           100
    autonegotiation: yes
    duplex mode:     full
    flowctrl:        none
    irq moderation:  disabled
    scatter-gather:  enabled


I already reported this issue about the 3C509B on LKML several month ago, but 
nobody could help. Ever since that mail I got several reports from other 
people having the same trouble with their cards.

Initially I wanted to write a bug report following the instructions 
in /usr/src/linux/Documentation/networking/vortex.txt, but since this seems 
to be more or less a general problem I don't know how to proceed now.


Thanks in advance,
 Bernd


-- 
Bernd Schubert
Physikalisch Chemisches Institut / Theoretische Chemie
Universität Heidelberg
INF 229
69120 Heidelberg
e-mail: bernd.schubert@xxxxxxxxxxxxxxxxxxxxx


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