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From "Gera Shegalov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-5649) Reduce cannot use more than 2G memory for the final merge
Date Thu, 16 Apr 2015 01:36:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-5649?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14497438#comment-14497438
] 

Gera Shegalov commented on MAPREDUCE-5649:
------------------------------------------

[~jlowe], [~kasha], please review if you get a chance.

> Reduce cannot use more than 2G memory  for the final merge
> ----------------------------------------------------------
>
>                 Key: MAPREDUCE-5649
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5649
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>            Reporter: stanley shi
>            Assignee: Gera Shegalov
>         Attachments: MAPREDUCE-5649.001.patch
>
>
> In the org.apache.hadoop.mapreduce.task.reduce.MergeManagerImpl.java file, in the finalMerge
method: 
>  int maxInMemReduce = (int)Math.min(
>         Runtime.getRuntime().maxMemory() * maxRedPer, Integer.MAX_VALUE);
>  
> This means no matter how much memory user has, reducer will not retain more than 2G data
in memory before the reduce phase starts.



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