[jira] [Commented] (LUCENE-6549) add MMapDirectory.preload

["Uwe Schindler (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-6549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14581885#comment-14581885 ] 

Uwe Schindler commented on LUCENE-6549:
---------------------------------------

Hi,
the patch is OK. But I have no strong opinion about this - I just would not use it, but anybody has the option now, so +1

We should just not make this the default or suggest anywhere to turn it on by default! The problem si: You have to load the data anywaysand I would prefer to do it as needed for faster startup time. It is also very bad for users who have not enough physical RAM, because it would load the stuff, invalidate a lot of active cache pages and then other stuff gets slower. I think the O/S does good job in paging, sorry! A short delay for some queries returning many results is not a problem for me (my personal opinion). But invalidating cache pages of more important stuff is bad.

> add MMapDirectory.preload
> -------------------------
>
>                 Key: LUCENE-6549
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6549
>             Project: Lucene - Core
>          Issue Type: Test
>            Reporter: Robert Muir
>         Attachments: LUCENE-6549.patch
>
>
> Patch to expose MappedByteBuffer.load() as a simple boolean option. 
> This can be used as an alternative to copy-into-RAMDirectory.
> Users who want sophisticated logic about this can use FileSwitchDirectory or other methods.



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