Subject: Re: Noatime vs relatime
From: Xavier Bestel <xavier.bestel@free.fr>
To: Vlad <vladc6@yahoo.com>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <233939.75965.qm@web54403.mail.yahoo.com>
References: <233939.75965.qm@web54403.mail.yahoo.com>
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Date: Fri, 10 Aug 2007 16:44:35 +0200
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On Fri, 2007-08-10 at 07:26 -0700, Vlad wrote:
> Relatime seems to be wasteful of both IO resources _and_ CPU cycles.
> Instead of performing a single IO operation (as atime does), relatime
> performs at least three IO operations and three CPU-dependent
> operations:
> 
> 1) a read IO operation to find out the old atime
> 2) a read IO operation to find out the old ctime
> 3) a read IO operation to find out the old mtime
> 4) Comparison of "old atime is <= than mtime/ctime"
> 5) Find out current time
> 6) Comparison of "current time minus old atime is > X"

As all [acm]times are stored in the same block (inode), I bet all this
is one single IO, plus some insignificant computation (3 comparisons
plus reading time is really smaller than one block IO).

	Xav


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