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https://issues.apache.org/jira/browse/LUCENE-2787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965740#action_12965740
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Michael McCandless commented on LUCENE-2787:
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+1, this is a no brainer. I had no idea linux lets you turn off atime per file
desriptor!
It's ridiculous that the OS maintains an atime on our index files.
Uwe, I agree about the intention of the man page (so eg back when
contrib/benchmark used to write 10,000 files to run its tests, and then index
them, we could've seen a big speedup :) ), but still it can't hurt to also turn
it off when opening the index files for reading.
I think atime is updated per-read not just at open
(http://lkml.org/lkml/1998/12/14/81) though I'm not sure. Even so, it's
presumably cached in the OS's write buffer and then only flushed periodically,
so I don't think we'll see sizable gains here. But every bit counts so I think
we should do it.
> 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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