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From "Alan Burlison (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-12012) Investigate JNI for improving byte array comparison performance
Date Thu, 21 May 2015 10:28:00 GMT
Alan Burlison created HADOOP-12012:
--------------------------------------

             Summary: Investigate JNI for improving byte array comparison performance
                 Key: HADOOP-12012
                 URL: https://issues.apache.org/jira/browse/HADOOP-12012
             Project: Hadoop Common
          Issue Type: Sub-task
          Components: benchmarks, io, performance
    Affects Versions: 2.7.0
         Environment: All
            Reporter: Alan Burlison
            Assignee: Alan Burlison
            Priority: Minor


HADOOP-7761 added functionality to compare byte arrays by treating them as arrays of 64-bit
longs for performance. However HADOOP-11466 reverted this change for the SPARC architecture
as it causes misaligned traps which causes performance to be worse rather than better.

Most platforms have a highly-optimised memcmp() libc function that uses processor-specific
functionality to perform byte array comparison as quickly as is possible for the platform.

We have done some preliminary benchmarking on Solaris that suggests that, for reasonably-sized
byte arrays, JNI code using memcmp() outperforms both of the current Java byte-size and long-size
implementations on both SPARC and x86 . We are confirming the results and will repeat the
same benchmark on Linux and report the results here for discussion.



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