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https://issues.apache.org/jira/browse/SPARK-33206?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17500272#comment-17500272
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Apache Spark commented on SPARK-33206:
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User 'attilapiros' has created a pull request for this issue:
https://github.com/apache/spark/pull/35714
> Spark Shuffle Index Cache calculates memory usage wrong
> -------------------------------------------------------
>
> Key: SPARK-33206
> URL: https://issues.apache.org/jira/browse/SPARK-33206
> Project: Spark
> Issue Type: Bug
> Components: Shuffle
> Affects Versions: 2.4.0, 3.0.1
> Reporter: Lars Francke
> Assignee: Attila Zsolt Piros
> Priority: Major
> Fix For: 3.3.0
>
> Attachments: image001(1).png
>
>
> SPARK-21501 changed the spark shuffle index service to be based on memory
> instead of the number of files.
> Unfortunately, there's a problem with the calculation which is based on size
> information provided by `ShuffleIndexInformation`.
> It is based purely on the file size of the cached file on disk.
> We're running in OOMs with very small index files (byte size ~16 bytes) but
> the overhead of the ShuffleIndexInformation around this is much larger (e.g.
> 184 bytes, see screenshot). We need to take this into account and should
> probably add a fixed overhead of somewhere between 152 and 180 bytes
> according to my tests. I'm not 100% sure what the correct number is and it'll
> also depend on the architecture etc. so we can't be exact anyway.
> If we do that we can maybe get rid of the size field in
> ShuffleIndexInformation to save a few more bytes per entry.
> In effect this means that for small files we use up about 70-100 times as
> much memory as we intend to. Our NodeManagers OOM with 4GB and more of
> indexShuffleCache.
>
>
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