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From "stanley shi (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MAPREDUCE-5649) Reduce cannot use more than 2G memory for the final merge
Date Mon, 25 Nov 2013 05:32:35 GMT
stanley shi created MAPREDUCE-5649:
--------------------------------------

             Summary: 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
    Affects Versions: trunk
            Reporter: stanley shi


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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