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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7761) Improve performance of raw comparisons
Date Fri, 21 Oct 2011 05:16:33 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13132339#comment-13132339
] 

Todd Lipcon commented on HADOOP-7761:
-------------------------------------

- The findbugs warning is bogus (Token-related)
- The failed tests are also security-related (not this JIRA)
- the new javac warnings are true, but there's no way to ignore them. This is from use of
sun.misc.Unsafe.
                
> Improve performance of raw comparisons
> --------------------------------------
>
>                 Key: HADOOP-7761
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7761
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: io, util
>    Affects Versions: 0.23.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hadoop-7761.txt
>
>
> Guava has a nice implementation of lexicographical byte-array comparison that uses sun.misc.Unsafe
to compare unsigned byte arrays long-at-a-time. Their benchmarks show it as being 2x more
CPU-efficient than the equivalent pure-Java implementation. We can easily integrate this into
WritableComparator.compareBytes to improve CPU performance in the shuffle.

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