linux-kernel - Re: [patch 2/3] ipc: use shifts to extract seq/idx

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Message-ID: <4BF57C78.4040606@colorfullife.com>
Date:	Thu, 20 May 2010 20:16:24 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	Nick Piggin <npiggin@...e.de>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [patch 2/3] ipc: use shifts to extract seq/idx

On 05/20/2010 09:00 AM, Nick Piggin wrote:
> All the ipc ids and sequences are signed integers, so power of 2
> sequence multiplier does not work so well. Convert it to use shifts,
> which improves generated code particularly in ipc_lock/ipc_lock_check
> fast paths.
>
>    
Have you checked the asm output?
I would expect that gcc auto-optimizes constant divides by power-of-two.

--
     Manfred
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