Re: 3c59x slow; debug=5 removes the error; why?

On Sat, 15 May 2004, Christian Ostheimer wrote:

> case 1): insmod 3c59x
>   30-80kB/s; 30% overrun errors

Given the direction of the transfer, I assume that you are talking 
about the Rx overruns that ifconfig displays. Rx overruns appear when 
the host is too slow for the incoming data, which leads to filling up 
all Rx buffers - at this point the card cannot receive any more 
packets and everyhting is dropped. This is not a normal situation and 
based on the description of your notebook it should be powerful enough 
to handle 100Mbit/s.

> case 2): insmod 3c59x debug=5
>   6-10MB/s; 0.02% overruns

This is a bit more normal, however the presence of overruns is still 
not a good sign. Furthermore, increasing "debug" leads to lower 
performance of the driver as time is spent on the calls to "printk", 
which should not increase transfer speed... So it's something to do 
with the timing and coupled with:

> PCI: Found IRQ 11 for device 0000:02:00.0
> PCI: Sharing IRQ 11 with 0000:00:1f.1

... makes me believe that it has something to do with the interrupt 
sharing. What is the device that is sharing the IRQ with the 3Com NIC?
Is is possible to disable this device in BIOS and see if the problem 
dissapears ?

> downloading from notebook to pc and file transfers by scp in both
> directions give full speed

Hmm, only Rx interrupts seem to be affected...

> Comparing tx and rx packets shows that ftp has 0.7MB tx packets with
> 33 MB rx and scp has only 0.2 MB tx with 33 MB rx.

That's probably because of the TCP retransmissions.

-- 
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: [email protected]




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