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From "zhihai xu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-6063) In sortAndSpill of MapTask.java, size is calculated wrongly when bufend < bufstart.
Date Tue, 02 Sep 2014 19:39:22 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-6063?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

zhihai xu updated MAPREDUCE-6063:
---------------------------------
    Status: Patch Available  (was: Open)

I attached a patch for review.

> In sortAndSpill of MapTask.java, size is calculated wrongly when bufend < bufstart.
> -----------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-6063
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6063
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv1, mrv2
>            Reporter: zhihai xu
>            Assignee: zhihai xu
>         Attachments: MAPREDUCE-6063.000.patch
>
>
> In sortAndSpill of MapTask.java, size is calculated wrongly when bufend < bufstart.
 we should change (bufvoid - bufend) + bufstart to (bufvoid - bufstart) + bufend.
> Should change
> {code}
>      long size = (bufend >= bufstart
>           ? bufend - bufstart
>           : (bufvoid - bufend) + bufstart) +
>                   partitions * APPROX_HEADER_LENGTH;
> {code}
> to:
> {code}
>      long size = (bufend >= bufstart
>           ? bufend - bufstart
>           : (bufvoid - bufstart) + bufend) +
>                   partitions * APPROX_HEADER_LENGTH;
> {code}
> It is because when wraparound happen (bufend < bufstart) ,  the size should 
> bufvoid - bufstart (bigger one) + bufend(small one).
> You can find similar code implementation in MapTask.java:
> {code}
>         mapOutputByteCounter.increment(valend >= keystart
>             ? valend - keystart
>             : (bufvoid - keystart) + valend);
> {code}



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