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https://issues.apache.org/jira/browse/SPARK-18787?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hyukjin Kwon updated SPARK-18787:
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    Labels: bulk-closed  (was: )

> spark.shuffle.io.preferDirectBufs does not completely turn off direct buffer 
> usage by Netty
> -------------------------------------------------------------------------------------------
>
>                 Key: SPARK-18787
>                 URL: https://issues.apache.org/jira/browse/SPARK-18787
>             Project: Spark
>          Issue Type: Bug
>    Affects Versions: 2.0.2
>            Reporter: Aniket Bhatnagar
>            Priority: Major
>              Labels: bulk-closed
>
> The documentation for the configuration spark.shuffle.io.preferDirectBufs 
> states that it will force all allocations from Netty to be on-heap but this 
> currently does not happen. The reason is that preferDirect parameter of 
> Netty's PooledByteBufAllocator doesn't completely eliminate use of off heap 
> by Netty. In order to completely stop netty from using off heap memory, we 
> need to set the following system properties:
> - io.netty.noUnsafe=true
> - io.netty.threadLocalDirectBufferSize=0
> The proposal is to set properties (using System.setProperties) when the 
> executor starts (before any of the Netty classes load) or document these 
> properties to hint users on how to completely eliminate Netty' off heap 
> footprint.



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