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Date: Wed, 1 Dec 2010 09:46:13 -0500 (EST)
From: "Uwe Schindler (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-2787) disable atime for
 DirectIOLinuxDirectory
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    [ https://issues.apache.org/jira/browse/LUCENE-2787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965701#action_12965701 ] 

Uwe Schindler commented on LUCENE-2787:
---------------------------------------

bq. The option exists specifically for apps like lucene... see the description from the man page!!!!

The intention behind the man page is not for the part of the app that manages the *index* itsself (like Lucene) - it is for the part of the app, that *reads* files *to index them* (so that would be the app that uses lucene and e.g. uses TIKA to read all files, this one should set noatime). The idea is to not mark the file as "accessed" when the virus scanner or the KDE/gnome file system browser indexes it.

Simon is right about setting it as a mount option.

> disable atime for DirectIOLinuxDirectory
> ----------------------------------------
>
>                 Key: LUCENE-2787
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2787
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: contrib/*
>            Reporter: Robert Muir
>             Fix For: 3.1, 4.0
>
>         Attachments: LUCENE-2787.patch
>
>
> In Linux's open():
> O_NOATIME
>     (Since Linux 2.6.8) Do not update the file last access time (st_atime in the inode) when the file is read(2). This flag is intended for use by indexing or backup programs, where its use can significantly reduce the amount of disk activity. This flag may not be effective on all filesystems. One example is NFS, where the server maintains the access time.
> So we should do this in our linux-specific DirectIOLinuxDirectory.
> Separately (offtopic), it would be better if this was a LinuxDirectory that only uses O_DIRECT when it should :)
> It would be nice to think about an optional modules/native for common platforms similar to what tomcat provides
> Its easier to test directories like this now (-Dtests.directory)...

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