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https://issues.apache.org/jira/browse/TEZ-1248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15371927#comment-15371927
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Hitesh Shah commented on TEZ-1248:
----------------------------------

Committing shortly. 

> Reduce slow-start should special case 1 reducer runs
> ----------------------------------------------------
>
>                 Key: TEZ-1248
>                 URL: https://issues.apache.org/jira/browse/TEZ-1248
>             Project: Apache Tez
>          Issue Type: Improvement
>    Affects Versions: 0.5.0
>         Environment: 20 node cluster running tez
>            Reporter: Gopal V
>            Assignee: Zhiyuan Yang
>            Priority: Critical
>         Attachments: TEZ-1248.1.patch
>
>
> Reducer slow-start has a performance problem for the small cases where there 
> is just 1 reducer for a case with a single wave.
> Tez knows the split count and wave count, being able to determine if the 
> cluster has enough spare capacity to run the reducer earlier for lower 
> latency in a N-mapper -> 1 reducer case.



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