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https://issues.apache.org/jira/browse/HIVE-16166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15929493#comment-15929493
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Misha Dmitriev commented on HIVE-16166:
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Hm, the same tests failed again. Now it starts to look suspicious. I'll
investigate...
> HS2 may still waste up to 15% of memory on duplicate strings
> ------------------------------------------------------------
>
> Key: HIVE-16166
> URL: https://issues.apache.org/jira/browse/HIVE-16166
> Project: Hive
> Issue Type: Improvement
> Reporter: Misha Dmitriev
> Assignee: Misha Dmitriev
> Attachments: ch_2_excerpt.txt, HIVE-16166.01.patch
>
>
> A heap dump obtained from one of our users shows that 15% of memory is wasted
> on duplicate strings, despite the recent optimizations that I made. The
> problematic strings just come from different sources this time. See the
> excerpt from the jxray (www.jxray.com) analysis attached.
> Adding String.intern() calls in the appropriate places reduces the overhead
> of duplicate strings with this workload to ~6%. The remaining duplicates come
> mostly from JDK internal and MapReduce data structures, and thus are more
> difficult to fix.
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