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From "Min Zhou (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-7339) Introduce a buffered checksum for avoiding frequently calls on Checksum.update()
Date Mon, 30 May 2011 06:02:47 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-7339?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Min Zhou updated HADOOP-7339:
-----------------------------

    Attachment: HADOOP-7339-v2.diff

fixed svn conflicts.

> Introduce a buffered checksum for avoiding frequently calls on Checksum.update()
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-7339
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7339
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: util
>            Reporter: Min Zhou
>             Fix For: 0.22.0
>
>         Attachments: HADOOP-7339-v1.diff, HADOOP-7339-v2.diff
>
>
> 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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