r8169 - disable flow-control?

r8169 - disable flow-control?

[Άλκης Γεωργόπουλος]

Hello,

Is there any way to disable flow control for NICs using the r8169
driver?

It would be really valuable in the following (sadly very common)
scenario:
 * r8169 gigabit NIC on the server
 * unmanaged gigabit switch that supports flow control negotiation
 * 100Mbps clients

E.g. in LTSP labs, the server can send data at ~900Mbps with flow
control off, but with flow control on the bandwidth drops to ~90Mbps.
Detailed explanation of the problem:
http://virtualthreads.blogspot.com/2006/02/beware-ethernet-flow-control.html

If the current code doesn't support it, would it be possible to add a
module parameter for this?

Kind regards,
Alkis Georgopoulos

Re: r8169 - disable flow-control?

[Ben Hutchings]

On Thu, 2009-03-05 at 21:35 +0200, Άλκης Γεωργόπουλος wrote:
> Hello,
> 
> Is there any way to disable flow control for NICs using the r8169
> driver?
> 
> It would be really valuable in the following (sadly very common)
> scenario:
>  * r8169 gigabit NIC on the server
>  * unmanaged gigabit switch that supports flow control negotiation
>  * 100Mbps clients
> 
> E.g. in LTSP labs, the server can send data at ~900Mbps with flow
> control off, but with flow control on the bandwidth drops to ~90Mbps.
> Detailed explanation of the problem:
> http://virtualthreads.blogspot.com/2006/02/beware-ethernet-flow-control.html
> 
> If the current code doesn't support it, would it be possible to add a
> module parameter for this?

Generally you should be able to control this using ethtool, not a module
parameter.  However r8169 does not implement this operation yet.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: r8169 - disable flow-control?

[Άλκης Γεωργόπουλος]

Στις 05-03-2009, ημέρα Πεμ, και ώρα 21:08 +0000, ο/η Ben Hutchings
έγραψε:
> Generally you should be able to control this using ethtool, not a module
> parameter.  However r8169 does not implement this operation yet.

Thanks - I just thought that supporting a module parameter (like e1000's
FlowControl=2) would be a small thing to ask, as opposed to supporting
ethtool.

But of course if ethtool is to be eventually supported by r8169, then
adding a parameter would be redundant.


Kind regards,
Alkis Georgopoulos