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Date: Thu, 07 Jul 2011 06:11:59 -0700 (PDT)
From: David Miller <davem@...emloft.net>
To: loke.chetan@...il.com
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, joe@...ches.com,
bhutchings@...arflare.com, shemminger@...tta.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next af-packet 1/2] Enhance af-packet to provide
(near zero)lossless packet capture functionality.
From: chetan loke <loke.chetan@...il.com>
Date: Thu, 7 Jul 2011 09:04:58 -0400
> On Thu, Jul 7, 2011 at 3:13 AM, David Miller <davem@...emloft.net> wrote:
>
>> Get rid of __packed__, it's going to kill performance on RISC
>> platforms. If you use __packed__, regardless of the actual alignment,
>
> The performance boost has been achieved by amortizing the cost of
> static spin-wait/poll and not by shrinking the data-set.
Chetan, if you're implementing something for performance reasons,
getting rid of packed is non-negotiable.
We pass data structures between userspace and the kernel all the
time, and without __packed__. We have mechanisms to ensure the
size of the individual data types, and we have mechanisms to make
sure 64-bit datums get aligned even on x86 (see "aligned_u64" and
friends")
Again, I can't seriously consider your patch if you keep the packed
attribute crap in there.
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