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https://issues.apache.org/jira/browse/SPARK-4550?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-4550:
-----------------------------------

    Assignee: Sandy Ryza  (was: Apache Spark)

> In sort-based shuffle, store map outputs in serialized form
> -----------------------------------------------------------
>
>                 Key: SPARK-4550
>                 URL: https://issues.apache.org/jira/browse/SPARK-4550
>             Project: Spark
>          Issue Type: Improvement
>          Components: Shuffle, Spark Core
>    Affects Versions: 1.2.0
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>            Priority: Critical
>         Attachments: SPARK-4550-design-v1.pdf, kryo-flush-benchmark.scala
>
>
> One drawback with sort-based shuffle compared to hash-based shuffle is that 
> it ends up storing many more java objects in memory.  If Spark could store 
> map outputs in serialized form, it could
> * spill less often because the serialized form is more compact
> * reduce GC pressure
> This will only work when the serialized representations of objects are 
> independent from each other and occupy contiguous segments of memory.  E.g. 
> when Kryo reference tracking is left on, objects may contain pointers to 
> objects farther back in the stream, which means that the sort can't relocate 
> objects without corrupting them.



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