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https://issues.apache.org/jira/browse/HBASE-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986866#action_12986866
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ryan rawson commented on HBASE-3455:
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we cannot replace the old value with the new one because there is no
way to atomically do that.


> Heap fragmentation in region server
> -----------------------------------
>
>                 Key: HBASE-3455
>                 URL: https://issues.apache.org/jira/browse/HBASE-3455
>             Project: HBase
>          Issue Type: Brainstorming
>          Components: performance, regionserver
>            Reporter: Todd Lipcon
>            Priority: Critical
>         Attachments: collapse-arrays.patch, HBasefragmentation.pdf, 
> icv-frag.png, mslab-1.txt, parse-fls-statistics.py, with-kvallocs.png
>
>
> Stop-the-world GC pauses have long been a problem in HBase. "Concurrent mode 
> failures" can usually be tuned around by setting the initiating occupancy 
> fraction low, but eventually the heap becomes fragmented and a promotion 
> failure occurs.
> This JIRA is to do research/experiments about the heap fragmentation issue 
> and possible solutions.

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