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From "Michael Busch (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-893) Increase buffer sizes used during searching
Date Sat, 26 May 2007 16:27:16 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12499325
] 

Michael Busch commented on LUCENE-893:
--------------------------------------

> Do you have any results for non-compound format?

I converted the index to non-cfs format and reran the same test,
varying the readBufferSize (i. e. the buffer size for all input
streams). 

Results for conjunction queries:

 1 KB: Time: 52422 ms.
 2 KB: Time: 47718 ms.
 4 KB: Time: 50078 ms.
 8 KB: Time: 54719 ms.
 
Results for disjunction queries:

 1 KB: Time: 291000 ms.
 2 KB: Time: 266110 ms.
 4 KB: Time: 258844 ms.
 8 KB: Time: 279812 ms. 
 
The results look similar to compound format here. Again 2 KB looks
like the best value.


> Increase buffer sizes used during searching
> -------------------------------------------
>
>                 Key: LUCENE-893
>                 URL: https://issues.apache.org/jira/browse/LUCENE-893
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Store
>    Affects Versions: 2.1
>            Reporter: Michael McCandless
>
> Spinoff of LUCENE-888.
> In LUCENE-888 we increased buffer sizes that impact indexing and found
> substantial (10-18%) overall performance gains.
> It's very likely that we can also gain some performance for searching
> by increasing the read buffers in BufferedIndexInput used by
> searching.
> We need to test performance impact to verify and then pick a good
> overall default buffer size, also being careful not to add too much
> overall HEAP RAM usage because a potentially very large number of
> BufferedIndexInput instances are created during searching
> (# segments X # index files per segment).

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