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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11466) FastByteComparisons: do not use UNSAFE_COMPARER on the SPARC architecture because it is slower there
Date Wed, 21 Jan 2015 20:54:35 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11466?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14286245#comment-14286245
] 

Hadoop QA commented on HADOOP-11466:
------------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12693678/HADOOP-11466.003.patch
  against trunk revision 925c9fe.

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include any new or modified
tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of
javac compiler warnings.

    {color:green}+1 javadoc{color}.  There were no new javadoc warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with eclipse:eclipse.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new Findbugs (version
2.0.3) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number
of release audit warnings.

    {color:green}+1 core tests{color}.  The patch passed unit tests in hadoop-common-project/hadoop-common.

Test results: https://builds.apache.org/job/PreCommit-HADOOP-Build/5444//testReport/
Console output: https://builds.apache.org/job/PreCommit-HADOOP-Build/5444//console

This message is automatically generated.

> FastByteComparisons: do not use UNSAFE_COMPARER on the SPARC architecture because it
is slower there
> ----------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-11466
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11466
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: io, performance, util
>         Environment: Linux X86 and Solaris SPARC
>            Reporter: Suman Somasundar
>            Assignee: Suman Somasundar
>            Priority: Minor
>              Labels: patch
>         Attachments: HADOOP-11466.002.patch, HADOOP-11466.003.patch
>
>
> One difference between Hadoop 2.x and Hadoop 1.x is a utility to compare two byte arrays
at coarser 8-byte granularity instead of at the byte-level. The discussion at HADOOP-7761
says this fast byte comparison is somewhat faster for longer arrays and somewhat slower for
smaller arrays ( AVRO-939). In order to do 8-byte reads on addresses not aligned to 8-byte
boundaries, the patch uses Unsafe.getLong. The problem is that this call is incredibly expensive
on SPARC. The reason is that the Studio compiler detects an unaligned pointer read and handles
this read in software. x86 supports unaligned reads, so there is no penalty for this call
on x86. 



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