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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-1743) MMapDirectory should only mmap large files, small files should be opened using SimpleFS/NIOFS
Date Tue, 14 Jul 2009 09:39:15 GMT
MMapDirectory should only mmap large files, small files should be opened using SimpleFS/NIOFS
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                 Key: LUCENE-1743
                 URL: https://issues.apache.org/jira/browse/LUCENE-1743
             Project: Lucene - Java
          Issue Type: Improvement
          Components: Store
    Affects Versions: 2.9
            Reporter: Uwe Schindler
            Assignee: Uwe Schindler
             Fix For: 3.1


This is a followup to LUCENE-1741:
Javadocs state (in FileChannel#map): "For most operating systems, mapping a file into memory
is more expensive than reading or writing a few tens of kilobytes of data via the usual read
and write methods. From the standpoint of performance it is generally only worth mapping relatively
large files into memory."
MMapDirectory should get a user-configureable size parameter that is a lower limit for mmapping
files. All files with a size<limit should be opened using a conventional IndexInput from
SimpleFS or NIO (another configuration option for the fallback?).

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