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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-6148) Implement a pure Java CRC32 calculator
Date Wed, 15 Jul 2009 23:39:14 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-6148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12731743#action_12731743
] 

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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