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Date: Tue, 14 Jul 2009 13:25:14 -0700 (PDT)
From: "Eks Dev (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-1743) MMapDirectory should only mmap
 large files, small files should be opened using SimpleFS/NIOFS
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    [ https://issues.apache.org/jira/browse/LUCENE-1743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12731104#action_12731104 ] 

Eks Dev commented on LUCENE-1743:
---------------------------------

right, it is not everything about reading index, you have to write it as well...

why not making  it an abstract class with 
abstract Directory getDirectory(String file, int minSize, int maxSize, String [read/write/append], String context);
String getName(); // for logging
   
What do you understand under "context"? Something along the lines /Give me directory for "segment merges", "read only" for search./ 
...Maybe one day we will have possibility not to kill OS cache by merging,


> MMapDirectory should only mmap large files, small files should be opened using SimpleFS/NIOFS
> ---------------------------------------------------------------------------------------------
>
>                 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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