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Posted to mapreduce-issues@hadoop.apache.org by "Ruibang He (JIRA)" <ji...@apache.org> on 2009/12/01 08:37:20 UTC
[jira] Updated: (MAPREDUCE-1248) Redundant memory copying in
StreamKeyValUtil
[ https://issues.apache.org/jira/browse/MAPREDUCE-1248?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Ruibang He updated MAPREDUCE-1248:
----------------------------------
Attachment: MAPREDUCE-1248-v1.0.patch
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
> 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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