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Posted to mapreduce-issues@hadoop.apache.org by "Steve Loughran (JIRA)" <ji...@apache.org> on 2012/05/07 04:52:49 UTC

[jira] [Commented] (MAPREDUCE-4229) Intern counter names in the JT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269335#comment-13269335 ] 

Steve Loughran commented on MAPREDUCE-4229:
-------------------------------------------

This could be good on large systems, but as the strings go into the PermGen space, people are going to have to be playing with the JVM options to make that large enough, so it's not without some consequences.
                
> Intern counter names in the JT
> ------------------------------
>
>                 Key: MAPREDUCE-4229
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4229
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>    Affects Versions: 1.0.2
>            Reporter: Todd Lipcon
>
> In our experience, most of the memory in production JTs goes to storing counter names (String objects and character arrays). Since most counter names are reused again and again, it would be a big memory savings to keep a hash set of already-used counter names within a job, and refer to the same object from all tasks.

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