[jira] [Assigned] (SPARK-43043) Improve the performance of MapOutputTracker.updateMapOutput

["Xingbo Jiang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-43043?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xingbo Jiang reassigned SPARK-43043:
------------------------------------

    Assignee: Xingbo Jiang

> Improve the performance of MapOutputTracker.updateMapOutput
> -----------------------------------------------------------
>
>                 Key: SPARK-43043
>                 URL: https://issues.apache.org/jira/browse/SPARK-43043
>             Project: Spark
>          Issue Type: Improvement
>          Components: Spark Core
>    Affects Versions: 3.3.2
>            Reporter: Xingbo Jiang
>            Assignee: Xingbo Jiang
>            Priority: Major
>
> Inside of MapOutputTracker, there is a line of code which does a linear find through a mapStatuses collection: https://github.com/apache/spark/blob/cb48c0e48eeff2b7b51176d0241491300e5aad6f/core/src/main/scala/org/apache/spark/MapOutputTracker.scala#L167  (plus a similar search a few lines down at https://github.com/apache/spark/blob/cb48c0e48eeff2b7b51176d0241491300e5aad6f/core/src/main/scala/org/apache/spark/MapOutputTracker.scala#L174)
> This scan is necessary because we only know the mapId of the updated status and not its mapPartitionId.
> We perform this scan once per migrated block, so if a large proportion of all blocks in the map are migrated then we get O(n^2) total runtime across all of the calls.
> I think we might be able to fix this by extending ShuffleStatus to have an OpenHashMap mapping from mapId to mapPartitionId. 



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