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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9601) Support native CRC on byte arrays
Date Thu, 06 Jun 2013 18:19:20 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13677334#comment-13677334
] 

Todd Lipcon commented on HADOOP-9601:
-------------------------------------

Hey Gopal. I'll take a look at this patch later today. Did you get a chance to try any benchmarks?
You should see good CPU savings even on something like a pseudo-distributed "hadoop fs -put"
of a 1GB file. I think there's also a micro-benchmark of the CRC32 stuff floating around in
the tree. Would be good to get some numbers before commit to make sure that it really does
help as we expect.
                
> Support native CRC on byte arrays
> ---------------------------------
>
>                 Key: HADOOP-9601
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9601
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: performance, util
>    Affects Versions: 3.0.0
>            Reporter: Todd Lipcon
>            Assignee: Gopal V
>              Labels: perfomance
>         Attachments: HADOOP-9601-trunk-rebase-2.patch, HADOOP-9601-trunk-rebase.patch,
HADOOP-9601-WIP-01.patch, HADOOP-9601-WIP-02.patch
>
>
> When we first implemented the Native CRC code, we only did so for direct byte buffers,
because these correspond directly to native heap memory and thus make it easy to access via
JNI. We'd generally assumed that accessing byte[] arrays from JNI was not efficient enough,
but now that I know more about JNI I don't think that's true -- we just need to make sure
that the critical sections where we lock the buffers are short.

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