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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7333) Performance improvement in PureJavaCrc32
Date Thu, 26 May 2011 20:28:47 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13039905#comment-13039905
] 

Tsz Wo (Nicholas), SZE commented on HADOOP-7333:
------------------------------------------------

> Looks like Nicholas and I were doing the same thing :) ...

Todd, this reminds me the fun when we were doing HADOOP-6166 and HADOOP-6148.

Eric, thanks for joining us.

> So, +1 pending Hudson results.

+1 patch looks good.  Let me run some more tests before committing this.

> Performance improvement in PureJavaCrc32
> ----------------------------------------
>
>                 Key: HADOOP-7333
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7333
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: util
>    Affects Versions: 0.21.0
>         Environment: Linux x64
>            Reporter: Eric Caspole
>            Assignee: Eric Caspole
>            Priority: Minor
>         Attachments: HADOOP-7333.patch
>
>
> I would like to propose a small patch to 
>   org.apache.hadoop.util.PureJavaCrc32.update(byte[] b, int off, int len)
> Currently the method stores the intermediate result back into the data member "crc."
I noticed this method gets
> inlined into DataChecksum.update() and that method appears as one of the hotter methods
in a simple hprof profile collected while running terasort and gridmix.
> If the code is modified to save the temporary result into a local and just once store
the final result back into the data member, it results in slightly more efficient hotspot
codegen.
> I tested this change using the the "org.apache.hadoop.util.TestPureJavaCrc32$PerformanceTest"
which is embedded in the existing unit test for this class, TestPureJavaCrc32 on a variety
of linux x64 AMD and Intel multi-socket and multi-core systems I have available to test.
> The patch removes several stores of the intermediate result to memory yielding a 0%-10%
speedup in the "org.apache.hadoop.util.TestPureJavaCrc32$PerformanceTest" which is embedded
in the existing unit test for this class, TestPureJavaCrc32.
>  
> If you use a debug hotspot JVM with -XX:+PrintOptoAssembly, you can see the intermediate
stores such as:
> 414     movq    R9, [rsp + #24] # spill
> 419     movl    [R9 + #12 (8-bit)], RDX # int ! Field PureJavaCrc32.crc
> 41d     xorl    R10, RDX        # int
> The patch results in just one final store of the fully computed value.

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