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From "Min Zhou (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-7339) Introduce a buffered checksum for avoiding frequently calls on Checksum.update()
Date Mon, 30 May 2011 05:26:47 GMT
Introduce a buffered checksum for avoiding frequently calls on Checksum.update()
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                 Key: HADOOP-7339
                 URL: https://issues.apache.org/jira/browse/HADOOP-7339
             Project: Hadoop Common
          Issue Type: Improvement
          Components: util
            Reporter: Min Zhou


We found that PureJavaCRC32/CRC32.update() is the TOP 1 of the methods consuming CPU in a
map side, and in reduce side, it cost a lots of CPU too.

IFileOutputStream would frequently call Checksum.update() during writing a record. It's very
common a MR key/value less than 512 bytes. Checksum.update() would be called every time writing
a key/value. 

Test case: terasort 100MB. 
Checksum.update() calls has be reduced from 4030348 to 28069.  This method is not a hotspot
anymore.




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