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https://issues.apache.org/jira/browse/MAPREDUCE-1248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12926043#action_12926043
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Hudson commented on MAPREDUCE-1248:
-----------------------------------
Integrated in Hadoop-Mapreduce-trunk-Commit #523 (See
[https://hudson.apache.org/hudson/job/Hadoop-Mapreduce-trunk-Commit/523/])
> 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
> Fix For: 0.22.0
>
> Attachments: MAPREDUCE-1248-v1.0.patch
>
>
> 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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