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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7339) Introduce a buffered checksum for avoiding frequently calls on Checksum.update()
Date Mon, 30 May 2011 05:42:47 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13041006#comment-13041006
] 

Hadoop QA commented on HADOOP-7339:
-----------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12480818/HADOOP-7339-v1.diff
  against trunk revision 1128789.

    +1 @author.  The patch does not contain any @author tags.

    -1 tests included.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    -1 patch.  The patch command could not apply the patch.

Console output: https://builds.apache.org/hudson/job/PreCommit-HADOOP-Build/538//console

This message is automatically generated.

> 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
>
>
> 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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