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Date:      Tue, 27 Aug 2013 07:53:40 +0200
From:      Hans Petter Selasky <hps@bitfrost.no>
To:        Michael Tuexen <tuexen@freebsd.org>
Cc:        freebsd-arm <freebsd-arm@FreeBSD.org>, Andre Oppermann <andre@freebsd.org>
Subject:   Re: ARM network trouble after recent mbuf changes
Message-ID:  <521C3EE4.80801@bitfrost.no>
In-Reply-To: <FF0E227A-0E15-4AFB-9BA0-E0E903D953F9@freebsd.org>
References:  <1377550636.1111.156.camel@revolution.hippie.lan> <521BC472.7040804@freebsd.org> <521BD531.4090104@sbcglobal.net> <FF0E227A-0E15-4AFB-9BA0-E0E903D953F9@freebsd.org>

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On 08/27/13 00:38, Michael Tuexen wrote:
> I did some tests with a small program. Having in struct pkthdr 64 bit entities
> results in a 64 bit alignment when used in struct mbuf. Using __packed
> for struct mbuf, removes the padding.


Hi,

Maybe you could use __aligned(8) instead, and account for the extra 
padding on all platforms? Packed has other disadvantages on ARM 
platforms when accessing the structures, like that non-aligned access is 
possible, and that it is sometimes slower than aligned access.

--HPS




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