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From "Joydeep Sen Sarma (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-2216) speculation should normalize progress rates based on amount of input data
Date Thu, 09 Dec 2010 20:08:03 GMT
speculation should normalize progress rates based on amount of input data
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                 Key: MAPREDUCE-2216
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2216
             Project: Hadoop Map/Reduce
          Issue Type: Bug
            Reporter: Joydeep Sen Sarma


We frequently see skews in data distribution both on the mappers and reducers. The small ones
finish quickly and the longer ones immediately get speculated. We should normalize progress
rates used by speculation with some metric correlated to the amount of data processed by the
task (like bytes read of rows processed). That will prevent these unnecessary speculations.

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