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https://issues.apache.org/jira/browse/SPARK-4921?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14261384#comment-14261384
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Sandy Ryza commented on SPARK-4921:
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Ah, makes sense. In the query, are some splits NODE_LOCAL and others NO_PREF?
Or all NO_PREF?
Looking deeper into the issue, as far as I can tell, changing the return value
to NO_PREF as described above should have no effect at all in any scenario.
> Performance issue caused by TaskSetManager returning PROCESS_LOCAL for
> NO_PREF tasks
> -------------------------------------------------------------------------------------
>
> Key: SPARK-4921
> URL: https://issues.apache.org/jira/browse/SPARK-4921
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 1.2.0
> Reporter: Xuefu Zhang
> Attachments: NO_PREF.patch
>
>
> During research for HIVE-9153, we found that TaskSetManager returns
> PROCESS_LOCAL for NO_PREF tasks, which may caused performance degradation.
> Changing the return value to NO_PREF, as demonstrated in the attached patch,
> seemingly improves the performance.
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