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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-6148) Implement a pure Java CRC32 calculator
Date Fri, 17 Jul 2009 01:11:14 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-6148?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated HADOOP-6148:
--------------------------------

    Attachment: hadoop-6148.txt

Woops! Forgot to do --no-prefix on my git-diff. Same patch, just without the a/ and b/ prefixes.

> 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: Todd Lipcon
>         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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