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From "Eks Dev (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1743) MMapDirectory should only mmap large files, small files should be opened using SimpleFS/NIOFS
Date Tue, 14 Jul 2009 20:25:14 GMT

    [ 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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