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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-7258) Tune DocIdSetBuilder allocation rate
Date Mon, 02 May 2016 12:03:12 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-7258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15266473#comment-15266473
] 

Robert Muir commented on LUCENE-7258:
-------------------------------------

If you have problems from large fixedbitsets, maybe the first thing to address is that top
level solr filter cache :)

> Tune DocIdSetBuilder allocation rate
> ------------------------------------
>
>                 Key: LUCENE-7258
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7258
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/spatial
>            Reporter: Jeff Wartes
>         Attachments: LUCENE-7258-Tune-memory-allocation-rate-for-Intersec.patch, LUCENE-7258-Tune-memory-allocation-rate-for-Intersec.patch,
allocation_plot.jpg
>
>
> LUCENE-7211 converted IntersectsPrefixTreeQuery to use DocIdSetBuilder, but didn't actually
reduce garbage generation for my Solr index.
> Since something like 40% of my garbage (by space) is now attributed to DocIdSetBuilder.growBuffer,
I charted a few different allocation strategies to see if I could tune things more. 
> See here: http://i.imgur.com/7sXLAYv.jpg 
> The jump-then-flatline at the right would be where DocIdSetBuilder gives up and allocates
a FixedBitSet for a 100M-doc index. (The 1M-doc index curve/cutoff looked similar)
> Perhaps unsurprisingly, the 1/8th growth factor in ArrayUtil.oversize is terrible from
an allocation standpoint if you're doing a lot of expansions, and is especially terrible when
used to build a short-lived data structure like this one.
> By the time it goes with the FBS, it's allocated around twice as much memory for the
buffer as it would have needed for just the FBS.



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