OutOfMemoryError when bootstrapping with less than 100GB RAM

Hi, I face an issue when bootstrapping a Node having less than 100GB RAM on our 10 Node C* 3.11.1 Cluster.

During bootstrap, when I watch the cassandra.log I observe a growth in JVM Heap Old Gen which gets not significantly freed up any more.

I know that JVM collects on Old Gen only when really needed. I can see collections, but there is always a remainder which seems to grow forever without ever getting freed.

After the Node successfully Joined the Cluster, I can remove the extra RAM I have given it for bootstrapping without any further effect.

It feels like Cassandra will not forget about every single byte streamed over the Network over time during bootstrapping, - which would be a memory leak and a major problem, too.

I was able to produce a HeapDumpOnOutOfMemoryError from a 56GB Node (40 GB assigned JVM Heap). YourKit Profiler shows huge amount of Memory allocated for org.apache.cassandra.db.Memtable (22 GB) org.apache.cassandra.db.rows.BufferCell (19 GB) and java.nio.HeapByteBuffer (11 GB)