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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10778) Use NativeCrc32 only if it is faster
Date Mon, 07 Jul 2014 18:00:37 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14053937#comment-14053937
] 

Todd Lipcon commented on HADOOP-10778:
--------------------------------------

BTW, I had suggested dynamically switching between java and native CRC32 about 5 years back,
but Owen said he'd veto that: https://issues.apache.org/jira/browse/HADOOP-6148?focusedCommentId=12721804&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-12721804

Perhaps he's changed his mind since then :)

The original JIRA also noted that OpenJDK was faster than Oracle's JDK at the time. So perhaps
that's the difference you're seeing between java 7 and java 6? Are you testing OpenJDK in
both cases or is it Oracle JDK 6?

> Use NativeCrc32 only if it is faster
> ------------------------------------
>
>                 Key: HADOOP-10778
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10778
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: util
>            Reporter: Tsz Wo Nicholas Sze
>            Assignee: Tsz Wo Nicholas Sze
>         Attachments: c10778_20140702.patch
>
>
> From the benchmark post in [this comment|https://issues.apache.org/jira/browse/HDFS-6560?focusedCommentId=14044060&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14044060],
NativeCrc32 is slower than java.util.zip.CRC32 for Java 7 and above when bytesPerChecksum
> 512.



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