netdev - Re: [PATCH] lib/checksum.c: optimize do

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Date:	Thu, 7 Jul 2011 12:32:45 +0100
From:	Ian Abbott <abbotti@....co.uk>
To:	David Miller <davem@...emloft.net>
CC:	Ian Abbott <ian.abbott@....co.uk>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lib/checksum.c: optimize do_csum a bit

On 07/07/11 12:29, David Miller wrote:
> From: Ian Abbott <abbotti@....co.uk>
> Date: Thu, 7 Jul 2011 12:18:49 +0100
> 
>> Reduce the number of variables modified by the loop in do_csum() by 1,
>> which seems like a good idea.  On Nios II (a RISC CPU with 3-operand
>> instruction set) it reduces the loop from 7 to 6 instructions, including
>> the conditional branch.
>>
>> Signed-off-by: Ian Abbott <abbotti@....co.uk>
> 
> I think you'll overshoot past the end of the buffer when there are
> trailing bytes to handle.
> 
> The whole reason we need the count variable is to handle those
> kinds of cases.

I don't think it does.  That's what the & ~3 was for.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-
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