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https://issues.apache.org/jira/browse/HBASE-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12987235#action_12987235
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Jonathan Gray commented on HBASE-3455:
--------------------------------------
A slight aside, but in a heavy concurrency increment-only use case we are CPU
bound with 80% or so being used in MemStore / CSLM operations. We are playing
with different ways of optimizing the MemStore+Increments use case. Today, it
takes between 3 and 4 CSLM operations for each increment. We should be able to
get this down to 1 or 2, but in all likelihood this would be an increment-only
optimization. Rather than modifying the original bytes in place, we are making
a new byte[] and modifying the KV to point at the new byte[]. This keeps the
modification atomic and prevents build-up (and costly removal) of KVs.
Will file a JIRA for this.
> 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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