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https://issues.apache.org/jira/browse/TEZ-394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15497122#comment-15497122
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Rohini Palaniswamy commented on TEZ-394:
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Have been running into resource issues and slowness in some jobs because of
this. In one particular job, where dataset A required 100 tasks and dataset X
required 35000 tasks , the scheduler ran dataset X first which took ~2 hrs and
then dataset A. This caused a lot of delay for the whole pipeline compared to
mapreduce.
> Better scheduling for uneven DAGs
> ---------------------------------
>
> Key: TEZ-394
> URL: https://issues.apache.org/jira/browse/TEZ-394
> Project: Apache Tez
> Issue Type: Sub-task
> Reporter: Rohini Palaniswamy
>
> Consider a series of joins or group by on dataset A with few datasets that
> takes 10 hours followed by a final join with a dataset X. The vertex that
> loads dataset X will be one of the top vertexes and initialized early even
> though its output is not consumed till the end after 10 hours.
> 1) Could either use delayed start logic for better resource allocation
> 2) Else if they are started upfront, need to handle failure/recovery cases
> where the nodes which executed the MapTask might have gone down when the
> final join happens.
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