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Date: Tue, 9 Feb 2010 18:33:28 +0000 (UTC)
From: "Arun C Murthy (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1463) Reducer should start faster for
 smaller jobs
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12831577#action_12831577 ] 

Arun C Murthy commented on MAPREDUCE-1463:
------------------------------------------

-1

These knobs seem backwards - as both Todd and Amar have pointed out we could add heuristics to tweak mapreduce.job.reduce.slowstart.completedmaps automatically without adding more config knobs.

> Reducer should start faster for smaller jobs
> --------------------------------------------
>
>                 Key: MAPREDUCE-1463
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1463
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: contrib/fair-share
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>         Attachments: MAPREDUCE-1463-v1.patch, MAPREDUCE-1463-v2.patch
>
>
> Our users often complain about the slowness of smaller ad-hoc jobs.
> The overhead to wait for the reducers to start in this case is significant.
> It will be good if we can start the reducer sooner in this case.

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