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Posted to mapreduce-dev@hadoop.apache.org by "Todd Lipcon (JIRA)" <ji...@apache.org> on 2012/05/20 23:44:41 UTC

[jira] [Created] (MAPREDUCE-4274) MapOutputBuffer should use native byte order for kvmeta

Todd Lipcon created MAPREDUCE-4274:
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             Summary: 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


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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