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Date: Fri, 28 Jan 2011 17:22:47 -0500 (EST)
From: "Todd Lipcon (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Subject: [jira] Updated: (HBASE-3455) Heap fragmentation in region server
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     [ https://issues.apache.org/jira/browse/HBASE-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Todd Lipcon updated HBASE-3455:
-------------------------------

    Attachment: mslab-3.txt

Oops, missed one test change before.

This patch should be good to go. I tested under heavy load (95% write, 5% increment, large working set to trigger block cache churn) on a cluster for about 16 hours, no full GCs at all in 8G heap with CMS.

But it's still off by default because of the worrisome theoretical possibilities with upsert.

> 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, mslab-2.txt, mslab-3.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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