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From "Robert Muir (JIRA)" <>
Subject [jira] [Commented] (LUCENE-4364) MMapDirectory makes too many maps for CFS
Date Thu, 06 Sep 2012 10:51:08 GMT


Robert Muir commented on LUCENE-4364:

it was an intermediate step. unlike unmaphack, its a little more broken for chunkSize to be
a setter.

with one of the previous patches, i noticed that if you were to change this at certain times
it could be bad news. so I wanted to prevent the possibility of problems... probably not an
isssue now.

> MMapDirectory makes too many maps for CFS
> -----------------------------------------
>                 Key: LUCENE-4364
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>         Attachments: 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

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