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From "Ruibang He (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1248) Redundant memory copying in StreamKeyValUtil
Date Tue, 01 Dec 2009 07:33:22 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12784098#action_12784098
] 

Ruibang He commented on MAPREDUCE-1248:
---------------------------------------

Thanks, Guanyin. The lastest trunk has fixed the problem in KeyValueLineRecordReader.java,
but in StreamKeyValUtil.java this problem still exists. Patch is attached for an early solution.

> Redundant memory copying in StreamKeyValUtil
> --------------------------------------------
>
>                 Key: MAPREDUCE-1248
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1248
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: contrib/streaming
>            Reporter: Ruibang He
>            Priority: Minor
>
> I found that when MROutputThread collecting the output of  Reducer, it calls StreamKeyValUtil.splitKeyVal()
and two local byte-arrays are allocated there for each line of output. Later these two byte-arrays
are passed to variable key and val. There are twice memory copying here, one is the System.arraycopy()
method, the other is inside key.set() / val.set().
> This causes double times of memory copying for the whole output (may lead to higher CPU
consumption), and frequent temporay object allocation.

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