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Re: XFS and noatime

To: xfs@xxxxxxxxxxx
Subject: Re: XFS and noatime
From: Markus Schoder <lists@xxxxxxxxxxxxxxxx>
Date: Sun, 28 May 2006 17:33:56 +0200
Cc: Markus Schoder <lists@xxxxxxxxxxxxxxxx>
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Christian Kujau wrote:
> On Sat, 27 May 2006, Markus Schoder wrote:
> > Seems that XFS updates the atime for binary files that are executed
> > even if noatime is specified on mount.
>
> And it does not happen only after executing files, as I'm writing
> this /etc/passwd's atime have changed (and no, nobody else is on the
> box ;))
>
> $ stat /etc/passwd
>    File: `/etc/passwd'
>    Size: 2441            Blocks: 8          IO Block: 4096   regular
> file Device: 805h/2053d      Inode: 8389875     Links: 1
> Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/  root)
> Access: 2006-05-28 04:43:18.553907666 +0100 
> Modify: 2006-05-27 01:39:39.319279976 +0100
> Change: 2006-05-27 01:39:39.329284198 +0100

Oh no, looks like mmaping a file also changes atime (checked it with a 
tiny test progam). The stat command mmaps /etc/passwd probably to look 
up username and groupname (implicitly through libc I guess).

This also explains why I get frequent disk accesses on a mostly idle 
box. Anybody knows wether this is easy to fix?

I am on 2.6.16.18, amd64 by the way.

--
Markus

PS: Would it be possible to keep me on CC since I am not subscribed?


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