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From "Thomas Graves (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4752) Reduce MR AM memory usage through String Interning
Date Wed, 31 Oct 2012 14:55:13 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13487833#comment-13487833
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Thomas Graves commented on MAPREDUCE-4752:
------------------------------------------

+1 Thanks Bobby! I'll commit this shortly
                
> Reduce MR AM memory usage through String Interning
> --------------------------------------------------
>
>                 Key: MAPREDUCE-4752
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4752
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: mrv2
>            Reporter: Robert Joseph Evans
>            Assignee: Robert Joseph Evans
>         Attachments: MR-4752-branch-0.23.txt, MR-4752-branch-0.23.txt, MR-4752-trunk.txt,
MR-4752-trunk.txt
>
>
> There are a lot of strings that are duplicates of one another in the AM.  This comes
from all of the PB events the come across the wire and also tasks heart-beating in through
the umbilical.  There are even several duplicates from Configuration.  By "interning" all
of these strings on the Heap I have been able to reduce the resting memory usage of the AM
to be about 5KB per task attempt.  With about half of this coming from counters.  This results
in a 5MB heap for a typical 1000 task job, or a 500MB heap for a 100,000 task attempt job.
 I think I could cut the size of the counters in half by completely rewriting how counters
work in the AM and History Server, but I don't think it is worth it at this point.
> I am still investigating what the memory usage of the AM is like when running very large
jobs, and I will probably have a follow-up JIRA for reducing that memory usage as well.

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