Re: 3c900 NIC slow under linux

From: Andrew Morton (andrewm@uow.edu.au)
Date: Fri May 12 2000 - 13:01:11 EST


Gianluca Anzolin wrote:
>
> I have recently replaced an Intel EtherExpress 16 card with a 3c900
> (Boomerang) 3Com card. The problem is that, when I'm receiving something
> from the 3Com card, it is rather slow: I can get only ~ 857Kb/s versus
> 1190 Kb/s with the same card under Windows 98 (40% faster, ie the same
> speed I got under linux with the Intel eexpress 16 card).
>
> There seems there is a problem in the driver and that problem shows only
> receiving data (not sending: I can happily send ~1,2 Mb/sec under
> linux). Could someone help me ?

Receive slow? That's odd.

What distro/kernel/driver version are you using?

Could you please:

- run 'ifconfig' after testing and send me the output? I'll be looking
at the collision count.

- Describe your setup - I assume it's hubbed 10bT? What is on the
sending machine? Sufficient info for me to reproduce this.

- Also, the output of 'vortex-diag' would be useful. There is info on
this at http://www.uow.edu.au/~andrewm/linux/vortex.txt . Thanks.

A good benchmark is netperf (http://www.netperf.org). This simply hoses
TCP at the other machine and reports on the throughput.

The 3c59x/3c905 combo _is_ slow on transmit. I usually see ~7 Mbits/sec
with netperf, whereas a lowly ISA ne2k can hit 10 Mbits/sec. I suspect
this is due to inefficient backoff. The 905's have extended deference
control which may allow this to be managed - the driver doesn't use
this.

Interesting indeed that W98 runs faster. The Linux driver is nice and
quick with full duplex 100bT - 92 Mbits/sec, which tends to confirm the
above theories.

I'd be reluctant to play with the deference control in the 2.2 or 2.3
drivers, but I'd be happy to use you as a guinea pig :)

-- 
-akpm-

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