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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:
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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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