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https://issues.apache.org/jira/browse/SPARK-14293?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-14293:
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Assignee: (was: Apache Spark)
> Improve shuffle load balancing and minmize network data transmission
> --------------------------------------------------------------------
>
> Key: SPARK-14293
> URL: https://issues.apache.org/jira/browse/SPARK-14293
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core
> Affects Versions: 1.6.1
> Reporter: Cheng Pei
> Labels: performance
>
> Currently Spark provides the mechanism to set preferred location for reduce
> task. When the fraction of total map output at a location is equal or greater
> than the parameter REDUCER_PREF_LOCS_FRACTION, the reduce task will get a
> preferred location. But this does not consider load balancing and network
> transmission. Based on the map output sizes and locations tracked by
> MapOutputTracker, we can obtain a better load balancing.
>
> This patch proposes a strategy to set preferred locations for each reduce
> task, which could firstly keep each executor process almost the same amount
> of intermediate data and secondly minimize the network data transmission.
> This can benefit some conditions:
> 1． REDUCER_PREF_LOCS_FRACTION tries to place the reduce tasks close to the
> largest output. If there exists data skew in the map outputs, it could cause
> some executors that have large of map outputs become busy. Our method could
> avoid this case and minimize the network data transmission.
> 2． When there are large of reduce tasks in the job, it helps each executor
> processes almost the same data and keeps load balancing.
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