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https://issues.apache.org/jira/browse/HADOOP-6148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12732465#action_12732465
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Hudson commented on HADOOP-6148:
--------------------------------
Integrated in Hadoop-Common-trunk #29 (See
[http://hudson.zones.apache.org/hudson/job/Hadoop-Common-trunk/29/])
. Implement a fast, pure Java CRC32 calculator which outperforms
java.util.zip.CRC32. Contributed by Todd Lipcon and Scott Carey
> Implement a pure Java CRC32 calculator
> --------------------------------------
>
> Key: HADOOP-6148
> URL: https://issues.apache.org/jira/browse/HADOOP-6148
> Project: Hadoop Common
> Issue Type: Improvement
> Components: util
> Reporter: Owen O'Malley
> Assignee: Scott Carey
> Fix For: 0.21.0
>
> Attachments: benchmarks20090714.txt, benchmarks20090715.txt,
> crc32-results.txt, hadoop-5598-evil.txt, hadoop-5598-hybrid.txt,
> hadoop-5598.txt, hadoop-5598.txt, hadoop-6148.txt, hadoop-6148.txt,
> hadoop-6148.txt, hdfs-297.txt, PureJavaCrc32.java, PureJavaCrc32.java,
> PureJavaCrc32.java, PureJavaCrc32.java, PureJavaCrc32New.java,
> PureJavaCrc32NewInner.java, PureJavaCrc32NewLoop.java,
> TestCrc32Performance.java, TestCrc32Performance.java,
> TestCrc32Performance.java, TestCrc32Performance.java, TestPureJavaCrc32.java
>
>
> We've seen a reducer writing 200MB to HDFS with replication = 1 spending a
> long time in crc calculation. In particular, it was spending 5 seconds in crc
> calculation out of a total of 6 for the write. I suspect that it is the
> java-jni border that is causing us grief.
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