netdev - Re: r8169 - disable flow-control?

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Date:	Thu, 05 Mar 2009 21:08:48 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Άλκης Γεωργόπουλος <alkisg@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: r8169 - disable flow-control?

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.

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