linux-kernel - Re: new ipdelay= option for faster netboot

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Message-Id: <20090817.180323.253692704.davem@davemloft.net>
Date:	Mon, 17 Aug 2009 18:03:23 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	tim.bird@...sony.com
Cc:	r.schwebel@...gutronix.de, vda.linux@...glemail.com,
	linux-kernel@...r.kernel.org, linux-embedded@...r.kernel.org,
	arjan@...ux.intel.com, kernel@...gutronix.de,
	netdev@...r.kernel.org
Subject: Re: new ipdelay= option for faster netboot

From: Tim Bird <tim.bird@...sony.com>
Date: Mon, 17 Aug 2009 15:35:01 -0700

> Tim Bird wrote:
>> See the definitions of CONF_PRE_OPEN and CON_POST_OPEN
>> in net/ipv4/ipconfig.c
>> 
>> They are set to ridiculously long values.  In my experience,
>> you can cut them down considerably with no dangerous side
>> effects (but I haven't asked the network guys about the
>> possible downsides).
> 
> It turns out that others have seen this delay.  Simon
> Arlott recently posted a patch to make the delay avoidable
> at boot time from the kernel command line.
> 
> See http://patchwork.kernel.org/patch/31678/

"Rediculiously long" is a relative term.

I have card/switch combinations that take up to 10 seconds to
negotiate a proper link.

So what's there now is actually a quite agressive setting.

And BTW, discussions about stuff like this belong on
netdev@...r.kernel.org, which has been added to the CC:
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