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https://issues.apache.org/jira/browse/FLINK-8809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16413978#comment-16413978
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Greg Hogan commented on FLINK-8809:
-----------------------------------
As you have noted this maximum value is set only for
[MaxDirectMemorySize|https://docs.oracle.com/javase/8/docs/technotes/tools/unix/java.html]
which constrains the "the maximum total size (in bytes) of the New I/O (the
java.nio package) direct-buffer allocations". Flink's allocation of memory
segments is controlled by its configuration so there is no need to constrain
this value in the JVM.
What would you choose as a reasonable default value? Requiring some users to
increase this value is a
[DRY|https://en.wikipedia.org/wiki/Don%27t_repeat_yourself] anti-pattern.
So I think the explanation to be: there is no harm in setting this to an
essentially "infinite" value, and no benefit to setting a lower value.
> Decrease maximum value of DirectMemory at default config
> --------------------------------------------------------
>
> Key: FLINK-8809
> URL: https://issues.apache.org/jira/browse/FLINK-8809
> Project: Flink
> Issue Type: Bug
> Components: TaskManager
> Reporter: Kirill A. Korinskiy
> Priority: Major
>
> Good day!
>
> Have I can see since this
> [commit|https://github.com/apache/flink/commit/6c44d93d0a9da725ef8b1ad2a94889f79321db73]
> TaskManager uses 8,388,607 terabytes as maximum out of heap memory. I guess
> that not any system has so much memory and it may be a reason to kill java
> process by OOM Killer.
>
> I suggest to decrease this value to reasonable value by default.
>
> Right now I see only one way to overstep this hardcoded value: setup
> FLINK_TM_HEAP to 0, and specified heap size by hand over
> FLINK_ENV_JAVA_OPTS_TM.
> Thanks
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