linux-kernel - Re: [PATCH] [1/2] Optimization for touch

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Date:	Tue, 7 Jul 2009 06:49:14 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] [1/2] Optimization for touch_atime

On Mon, Jul 06, 2009 at 09:24:46PM +0200, Andi Kleen wrote:
> 
> Some benchmark testing shows touch_atime to be high up in profile
> logs for IO intensive workloads. Most likely that's due to the lock
> in mnt_want_write().  Unfortunately touch_atime first takes the lock,
> and then does all the other tests that could avoid atime updates (like
> noatime or relatime).
> 
> Do it the other way round -- first try to avoid the update and only
> then if that didn't succeed take the lock. That works because none of
> the atime avoidance tests rely on locking.
> 
> This also eliminates a goto.
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>


Looks good to me.
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