Erasure Coding: Native library memory leak

We use both apache-hadoop-3.1.3 and CDH-6.1.1-1.cdh6.1.1.p0.875250 HDFS in production, and both of them have the memory increasing over -Xmx value. 

We use EC strategy to to save storage costs.

This's the jvm options:

-Dproc_datanode -Dhdfs.audit.logger=INFO,RFAAUDIT -Dsecurity.audit.logger=INFO,RFAS -Djava.net.preferIPv4Stack=true -Xms8589934592 -Xmx8589934592 -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=70 -XX:+CMSParallelRemarkEnabled -XX:+HeapDumpOnOutOfMemoryError ...

The max jvm heapsize is 8GB, but we can see the datanode RSS memory is 48g. All the other datanodes in this hdfs cluster has the same issue.

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 
226044 hdfs 20 0 50.6g 48g 4780 S 90.5 77.0 14728:27 /usr/java/jdk1.8.0_162/bin/java -Dproc_datanode

This too much memory used leads to my machine unresponsive(if enable swap), or oom-killer happens.