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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-1248) Redundant memory copying in StreamKeyValUtil
Date Fri, 29 Oct 2010 02:05:34 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12926043#action_12926043
] 

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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