Ethernet driver general problem ....

Ethernet driver general problem ....

[Matti Aarnio]

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

Re: Ethernet driver general problem ....

[Andy Fleming]

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
>

Re: Ethernet driver general problem ....

[Francois Romieu]

Matti Aarnio <matti.aarnio@zmailer.org> :
[...]
> Comments ?  Suggestions ?

See the use of ethtool_ops.set_ringparam() below drivers/net.

--
Ueimor