azagrebin edited a comment on issue #11109: [FLINK-15758][MemManager] Release 
segment and its unsafe memory in GC Cleaner
URL: https://github.com/apache/flink/pull/11109#issuecomment-588878235
 
 
   I commented more in 
[FLINK-15094](https://issues.apache.org/jira/browse/FLINK-15094) about warning 
problem. There may be other workarounds to silence the warning.
   
   Also some more thoughts about the netty pooling approach.
   It contributes to direct memory limit which makes it hard to use 
interchangeably the native memory for managed batch and stream RocksDB.
   If we do not want to use cleaners (this PR, btw they also look like being an 
official tool in future Java), netty also uses reference counting. In this case 
to not rely on GC, every time memory segment issues a ByteBuffer view and 
increments the ref counter, the user code has to explicitly decrement it at 
some point and ensure that the ByteBuffer view will never be used afterwards. 
It is hard because the ByteBuffer view can be subsequently duplicated and/or 
sliced without contributing to ref counting.
   I can look more into this, maybe I overlook something.

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