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https://issues.apache.org/jira/browse/MAPREDUCE-4752?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13486294#comment-13486294
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Robert Joseph Evans commented on MAPREDUCE-4752:
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The test failure is caused by the Interning. I am working on a fix for it now.
Should have a new patch 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-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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