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Date: Thu, 20 Jan 2011 13:13:44 -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: parse-fls-statistics.py

Here's the python script I use to convert the FLS statistics log into a TSV format for graphing.

I was using the following flags with JVM 6u23:
-XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintTenuringDistribution -verbose:gc -Xloggc:$HBASE_HOME/logs/gc-$(hostname)-hbase.log
-XX:PrintCMSStatistics=1 -XX:PrintFLSStatistics=1

Might need to fiddle with the regex in the script if you use different flags or a different JVM release.

> 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: HBasefragmentation.pdf, parse-fls-statistics.py
>
>
> 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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