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https://issues.apache.org/jira/browse/FLINK-4094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15404120#comment-15404120
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Maximilian Michels commented on FLINK-4094:
-------------------------------------------

Yes, it was undocumented. Initially, I thought preallocation:false would just 
lazily pool when, in fact, it actually returned memory. In the offheap case 
this memory was never freed because the garbage collection of offheap memory 
only kicks in when the direct memory size limit is reached (or when a full 
garbage collection occurs in the meantime). For the regular heap case, it 
actually frees memory during normal garbage collection cycles.

> Off heap memory deallocation might not properly work
> ----------------------------------------------------
>
>                 Key: FLINK-4094
>                 URL: https://issues.apache.org/jira/browse/FLINK-4094
>             Project: Flink
>          Issue Type: Bug
>          Components: Local Runtime
>    Affects Versions: 1.1.0
>            Reporter: Till Rohrmann
>            Assignee: ramkrishna.s.vasudevan
>            Priority: Critical
>             Fix For: 1.1.0
>
>
> A user reported that off-heap memory is not properly deallocated when setting 
> {{taskmanager.memory.preallocate:false}} (per default) [1]. This can cause 
> the TaskManager process being killed by the OS.
> It should be possible to execute multiple batch jobs with preallocation 
> turned off. No longer used direct memory buffers should be properly garbage 
> collected so that the JVM process does not exceed it's maximum memory bounds.
> [1] 
> http://apache-flink-mailing-list-archive.1008284.n3.nabble.com/offheap-memory-allocation-and-memory-leak-bug-td12154.html



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