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Posted to dev@lucene.apache.org by "Yonik Seeley (JIRA)" <ji...@apache.org> on 2016/04/26 21:51:13 UTC
[jira] [Comment Edited] (LUCENE-7258) Tune DocIdSetBuilder
allocation rate
[ https://issues.apache.org/jira/browse/LUCENE-7258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15258773#comment-15258773 ]
Yonik Seeley edited comment on LUCENE-7258 at 4/26/16 7:50 PM:
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Seems like we should do the same thing that was done for SOLR-8922 - Don't reallocate a single array, keep a list of them.
For extra credit, one could even try to eliminate the cost of coalescing all of the arrays into a single one by incorporating that step into the first step of the radix sort.
was (Author: yseeley@gmail.com):
Seems like we should do the same thing that was done for SOLR-8922 - Don't reallocate a single array, keep a list of them.
> 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
>
> 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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