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Posted to common-dev@hadoop.apache.org by "Matei Zaharia (JIRA)" <ji...@apache.org> on 2008/11/16 00:56:46 UTC

[jira] Updated: (HADOOP-4666) Launch reduces only after a few maps have run in the Fair Scheduler

     [ https://issues.apache.org/jira/browse/HADOOP-4666?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Matei Zaharia updated HADOOP-4666:
----------------------------------

    Issue Type: Improvement  (was: New Feature)

> Launch reduces only after a few maps have run in the Fair Scheduler
> -------------------------------------------------------------------
>
>                 Key: HADOOP-4666
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4666
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: contrib/fair-share
>            Reporter: Matei Zaharia
>
> It makes no sense to schedule reduces for a job before its maps have started running. As an initial fix, we will wait until a certain percent have run (likely 10%). In the future it would be good to choose the time to wait based on amount of map output data as well - launching reducers that will mostly be idle is not helpful. Average amount of map output bytes per mapper is easy to compute using counters in JobInProgress.

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