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Re: Ethernet driver general problem ....

To: Matti Aarnio <matti.aarnio@xxxxxxxxxxx>
Subject: Re: Ethernet driver general problem ....
From: Andy Fleming <afleming@xxxxxxxxxxxxx>
Date: Thu, 9 Jun 2005 16:04:48 -0500
Cc: netdev@xxxxxxxxxxx
In-reply-to: <20050609205348.GT4661@mea-ext.zmailer.org>
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Look into ethtool. ethtool allows you to configure the ring sizes, among other things.

On Jun 9, 2005, at 15:53, Matti Aarnio wrote:

I encountered today a case, where default RX_RING_SIZE
was too small for the traffic going thru.  (3c59x driver,
and NAT-router application.)

One related problem is, that the RING_SIZE is hard #define
parameter in most driver sources without ability to adjust
it during runtime.  (e.g.  "modprobe zzzz rx_ring_size=512")
Possibly even an  ifconfig:able  parameter, which works
also for statically compiled kernels.  (But needs new
ifconfig machinery...)


The case at hand was solved by editing kernel sources, and compiling a new kernel, but now I am looking for a more generic approach.


Clearly pre-allocing 500 buffers of 1.6 kB in size does eat a bit much of kernel memory which usual workstation does not get benefit from, but server or router would get benefits.

Having the rx_ring_size  ifconfig  tunable would help with
adjusting interface for reception, but adding ifconfig
parameters is ... not trivial.

Alternate might be  sysctl  tunability -- even as a global
'dev.eth.rx_ring_size' (or  'net.dev.eth.rx_ring_size')
which supplies (default) ring size for initialization of
the interface where such rings exist at all...


Possibly there should also be tx_ring_size, which need not be same size as the rx_ring_size.

Unadjusted default value for both could be 16.


All in all, this needs near uniquitous changes in driver init codes accross lots of network drivers.


Comments ? Suggestions ?

  /Matti Aarnio



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