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From "Adam Fuchs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-599) investigate permgen collection and class unloading with concurrent mark and sweep garbage collector
Date Fri, 25 May 2012 13:08:23 GMT

    [ 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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