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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-4274) MapOutputBuffer should use native byte order for kvmeta
Date Mon, 21 May 2012 19:09:41 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13280375#comment-13280375

Todd Lipcon commented on MAPREDUCE-4274:

Thanks Bobby!
> MapOutputBuffer should use native byte order for kvmeta
> -------------------------------------------------------
>                 Key: MAPREDUCE-4274
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4274
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: performance, task
>    Affects Versions: 2.0.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>             Fix For: 2.0.0, 3.0.0
>         Attachments: mapreduce-4274.txt
> I don't have a benchmark to support this, but this should give a small CPU improvement
on the map output buffer: currently, we create {{kvmeta}} as {{ByteBuffer.wrap(kvbuffer).asIntBuffer()}}.
According to the javadocs, the resulting int buffer will inherit its byte order from the ByteBuffer
it comes from, and the byte buffer defaults to BIG_ENDIAN. Thus, all of our int access to/from
the buffer will require byte-swapping.

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