From: Andi Kleen <ak@suse.de>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: netdev@oss.sgi.com
Subject: Re: reasons for dev_alloc_skb +16?
Date: Wed, 9 Jul 2003 17:53:55 +0200 [thread overview]
Message-ID: <20030709175355.422545b5.ak@suse.de> (raw)
In-Reply-To: <20030709152553.GB15293@gtf.org>
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
next prev parent reply other threads:[~2003-07-09 15:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-09 15:25 reasons for dev_alloc_skb +16? Jeff Garzik
2003-07-09 15:53 ` Andi Kleen [this message]
2003-07-09 16:06 ` Jeff Garzik
2003-07-09 16:13 ` Andi Kleen
2003-07-10 0:20 ` David S. Miller
-- strict thread matches above, loose matches on Subject: below --
2003-07-09 15:35 Hen, Shmulik
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