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https://issues.apache.org/jira/browse/HADOOP-6148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12731743#action_12731743
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Tsz Wo (Nicholas), SZE commented on HADOOP-6148:
------------------------------------------------
Thanks, Scott and Todd for checking the performance in such great details!
> I say we commit the NewInnerOnly version.
+1
BTW, the path for TestPureJavaCrc32 is wrong in the previous patch. We don't
have "core" directory anymore.
{code}
--- /dev/null
+++ src/test/core/org/apache/hadoop/util/TestPureJavaCrc32.java
@@ -0,0 +1,94 @@
{code}
> Implement a pure Java CRC32 calculator
> --------------------------------------
>
> Key: HADOOP-6148
> URL: https://issues.apache.org/jira/browse/HADOOP-6148
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Owen O'Malley
> Assignee: Todd Lipcon
> Attachments: benchmarks20090714.txt, benchmarks20090715.txt,
> crc32-results.txt, hadoop-5598-evil.txt, hadoop-5598-hybrid.txt,
> hadoop-5598.txt, hadoop-5598.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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