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Date: Fri, 25 May 2012 13:08:23 +0000 (UTC)
From: "Adam Fuchs (JIRA)" <jira@apache.org>
To: dev@accumulo.apache.org
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Subject: [jira] [Commented] (ACCUMULO-599) investigate permgen collection
 and class unloading with concurrent mark and sweep garbage collector
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    [ https://issues.apache.org/jira/browse/ACCUMULO-599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13283364#comment-13283364 ] 

Adam Fuchs commented on ACCUMULO-599:
-------------------------------------

Sounds like we ought to reach out to a Java GC guru with this question.

My philosophy would be that we should pull in whatever configs we think make sense and then thoroughly test. Waiting for bugs to show up could mask the potential for performance improvement.
                
> investigate permgen collection and class unloading with concurrent mark and sweep garbage collector
> ---------------------------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-599
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-599
>             Project: Accumulo
>          Issue Type: Bug
>          Components: scripts
>    Affects Versions: 1.3.6, 1.4.0
>            Reporter: Adam Fuchs
>            Assignee: John Vines
>
> The Java concurrent mark and sweep garbage collector appears to default to not unloading classes or sweeping the permgen storage space. Accumulo reloads classes dynamically, potentially contributing a lot to the permgen space. It is important that these classes be garbage collected when we're done with them. Since we use -XX:+UseConcMarkSweepGC by default for all Accumulo processes, should we also use -XX:+CMSClassUnloadingEnabled and -XX:+CMSPermGenSweepingEnabled? Are there other flags or parameters that we should set to really do java garbage collection properly in a long-lived instance?
> These should be set in conf/accumulo-env.sh as part of ACCUMULO_GENERAL_OPTS.

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