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From "Vinod K V (JIRA)" <j...@apache.org>
Subject [jira] Updated: (MAPREDUCE-1829) JobInProgress.findSpeculativeTask should use min() to find the candidate instead of sort()
Date Sat, 12 Jun 2010 09:58:14 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-1829?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vinod K V updated MAPREDUCE-1829:
---------------------------------

          Status: Resolved  (was: Patch Available)
    Hadoop Flags: [Reviewed]
    Release Note: Improved performance of the method JobInProgress.findSpeculativeTask() which
is in the critical heartbeat code path.
      Resolution: Fixed

I just committed this to trunk. Thanks Scott!

> JobInProgress.findSpeculativeTask should use min() to find the candidate instead of sort()
> ------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1829
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1829
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>    Affects Versions: 0.22.0
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>             Fix For: 0.22.0
>
>         Attachments: MAPREDUCE-1829-20100610.txt, MAPREDUCE-1829.txt
>
>
> findSpeculativeTask needs only one candidate to speculate so it does not need to sort
the whole list. It may looks OK but someone can still submit big jobs with small slow task
thresholds. In this case, this sorting becomes expensive.

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