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https://issues.apache.org/jira/browse/HBASE-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986840#action_12986840
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Tatsuya Kawano commented on HBASE-3455:
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Maybe this is not an optimal solution but how about this? Forget about
reclaiming individual free spaces from old cell values, but pretend them as
live spaces and let Memstore to flush. Memstore flusher won't write old cell
values to HFile as they are not referenced from the Memstore.
You could get a stupid smaller HFiles if you do lots of ICVs, but a minor
compaction will soon merge them into one moderate-sized HFile, so it's not
going to be a problem.
> 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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