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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (LUCENE-4364) MMapDirectory makes too many maps for CFS
Date Thu, 06 Sep 2012 08:43:08 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-4364?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Uwe Schindler updated LUCENE-4364:
----------------------------------

    Attachment: LUCENE-4364.patch

I combined the slicing and clone methods to be one. When doing this it now also supports slicing
clones or slicing slices (as offset is added). I commented out the IllegalStateException,
but we can reenable it to disallow.
I also made in the abstract class all methods reading from buffers final, to help Hotspot
(MMapIndexInput is already final, but this makes it more reuseable).
I also removed the class name from some Exception messages like AlreadyClosed, because the
toString() method already contains type.
                
> MMapDirectory makes too many maps for CFS
> -----------------------------------------
>
>                 Key: LUCENE-4364
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4364
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>         Attachments: LUCENE-4364.patch, LUCENE-4364.patch, LUCENE-4364.patch, LUCENE-4364.patch,
LUCENE-4364.patch
>
>
> While looking at LUCENE-4123, i thought about this:
> I don't like how mmap creates a separate mapping for each CFS slice, to me this is way
too many mmapings.
> Instead I think its slicer should map the .CFS file, and then when asked for an offset+length
slice of that, it should be using .duplicate()d buffers of that single master mapping.
> then when you close the .CFS it closes that one mapping.
> this is probably too scary for 4.0, we should take our time, but I think we should do
it.

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