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From "Ben West (JIRA)" <>
Subject [Lucene.Net] [jira] [Commented] (LUCENENET-425) MMapDirectory implementation
Date Tue, 14 Jun 2011 21:24:47 GMT


Ben West commented on LUCENENET-425:

Unfortunately (or perhaps fortunately in that Digy doesn't need to do more work :-) MMap is
slower on 64 bit too. Index is 2.2gb.

Create index, FSDir:   419061
Create index, MMapdir: 532536
Search index, FSDir:   757
Search index, MMapdir: 2030

Reversing order:

Search index, FSDir: 734
Search index, MMap dir: 1934

I have 8gb ram, so I think the entire index was able to be cached in memory by the OS. 

> MMapDirectory implementation
> ----------------------------
>                 Key: LUCENENET-425
>                 URL:
>             Project: Lucene.Net
>          Issue Type: New Feature
>    Affects Versions: Lucene.Net 2.9.4g
>            Reporter: Digy
>            Priority: Trivial
>             Fix For: Lucene.Net 2.9.4g
>         Attachments: MMapDirectory.patch
> Since this is not a direct port of, I'll put it under "Support" and
implement MMapDirectory as 
> {code}
> public class MMapDirectory:Lucene.Net.Support.MemoryMappedDirectory
> {
> }
> {code}
> If a Mem-Map can not be created(for ex, if the file is too big to fit in 32 bit address
range), it will default to FSDirectory.FSIndexInput
> In my tests, I didn't see any performance gain in 32bit environment and I consider it
as better then nothing. 
> I would be happy if someone could send test results on 64bit platform.

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