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From "Jason Rutherglen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-753) Use NIO positional read to avoid synchronization in FSIndexInput
Date Mon, 30 Jun 2008 12:57:45 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-753?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609226#action_12609226
] 

Jason Rutherglen commented on LUCENE-753:
-----------------------------------------

Interesting results.  The question would be, what would the algorithm for allocating RandomAccessFiles
to which file look like?  When would a new file open, when would a file be closed?  If it
is based on usage would it be based on the rate of calls to readInternal?  This seems like
an OS filesystem topic that maybe there is some standard algorithm for.   How would the pool
avoid the same synchronization issue given the default small buffer size of 1024?  If there
are 30 threads executing searches, there will not be 30 RandomAccessFiles per file so there
is still contention over the limited number of RandomAccessFiles allocated.   

> Use NIO positional read to avoid synchronization in FSIndexInput
> ----------------------------------------------------------------
>
>                 Key: LUCENE-753
>                 URL: https://issues.apache.org/jira/browse/LUCENE-753
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Store
>            Reporter: Yonik Seeley
>         Attachments: FileReadTest.java, FileReadTest.java, FileReadTest.java, FileReadTest.java,
FSIndexInput.patch, FSIndexInput.patch, lucene-753.patch
>
>
> As suggested by Doug, we could use NIO pread to avoid synchronization on the underlying
file.
> This could mitigate any MT performance drop caused by reducing the number of files in
the index format.

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