linux-kernel - Re: problems with e1000 and jumboframes

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Message-ID: <Pine.LNX.4.64.0608031705560.8443@bizon.gios.gov.pl>
Date:	Thu, 3 Aug 2006 17:08:51 +0200 (CEST)
From:	Krzysztof Oledzki <olel@....pl>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
cc:	Arnd Hannemann <arnd@...dnet.de>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: problems with e1000 and jumboframes



On Thu, 3 Aug 2006, Evgeniy Polyakov wrote:
<CUT>
>> Why? After your explanation that makes sense for me. The driver needs
>> one contiguous chunk for those 9k packet buffer and thus requests a
>> 3-order page of 16k. Or do i still do not understand this?
>
> Correct, except that it wants 32k.
> e1000 logic is following:
> align frame size to power-of-two,
16K?

> then skb_alloc adds a little
> (sizeof(struct skb_shared_info)) at the end, and this ends up
> in 32k request just for 9k jumbo frame.

Strange, why this skb_shared_info cannon be added before first alignment? 
And what about smaller frames like 1500, does this driver behave similar 
(first align then add)?

Best regards,

 				Krzysztof Olędzki