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https://issues.apache.org/jira/browse/HADOOP-4788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12688425#action_12688425
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Chris Douglas commented on HADOOP-4788:
---------------------------------------

# This did not update CHANGES.txt
# This was not reviewed before it was committed

Since this is noncontroversial, I'll +1 it after the fact. Please update the 
changelog and only commit patches that have been reviewed.

> Set mapred.fairscheduler.assignmultiple to true by default
> ----------------------------------------------------------
>
>                 Key: HADOOP-4788
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4788
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: contrib/fair-share
>            Reporter: Matei Zaharia
>            Assignee: Matei Zaharia
>            Priority: Trivial
>             Fix For: 0.21.0
>
>         Attachments: hadoop-4788-v0.patch
>
>
> Pretty much all users of the fair scheduler are using the "assignmultiple" 
> feature which lets it launch reduce tasks at the same time as map tasks (on 
> the same heartbeats), leading to reduces starting faster. This is also going 
> to happen in Hadoop by default in HADOOP-3136. So we should set it to true by 
> default and perhaps even remove the config parameter.

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