From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <ak@suse.de>
Subject: Re: reasons for dev_alloc_skb +16?
Date: Wed, 9 Jul 2003 17:53:55 +0200
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To: Jeff Garzik <jgarzik@pobox.com>
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On Wed, 9 Jul 2003 11:25:53 -0400
Jeff Garzik <jgarzik@pobox.com> wrote:

> I knew this at one time, but have forgotten it :)
> 
> What is the reason for adding 16 to the dev_alloc_skb length?
> (and skb_reserve of the same length)

For the skb_reserve alignment to align the IP header. 

But it's not clear it is still a good idea because it leads to cache line 
misalignment of the beginning of the packet, forcing the card to do a
costly Read-Modify-Write cycle.

-Andi