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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (LUCENE-2825) FSDirectory.open should return MMap on 64-bit Solaris
Date Mon, 20 Dec 2010 14:43:01 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12973213#action_12973213
] 

Uwe Schindler edited comment on LUCENE-2825 at 12/20/10 9:41 AM:
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bq. Doesn't MMap automatically consume a lot more memory?

No, it consumes *address space*, this is why it only works without problems on 64 bit. The
index files are mapped into address space, so handled like a SWAP file, that's the trick.
They only consume as much memory from cache space as the operating system decides. Especially
it does not consume memory from java heap!


      was (Author: thetaphi):
    bq. Doesn't MMap automatically consume a lot more memory?

No, it consumes *address space*, this is why it only works on 64 bit. The index files are
mapped into address space, so handled like a SWAP file. They only consume as much memory from
cache space as the operating system decides. Especially it does not consume memory from java
heap!

  
> FSDirectory.open should return MMap on 64-bit Solaris
> -----------------------------------------------------
>
>                 Key: LUCENE-2825
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2825
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Store
>            Reporter: Robert Muir
>             Fix For: 3.1, 4.0
>
>         Attachments: LUCENE-2825.patch
>
>
> MMap is ~ 30% faster than NIOFS on this platform.

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