public static void clean(ByteBuffer byteBuffer) {
    if (byteBuffer instanceof MappedByteBuffer) {
      clean((MappedByteBuffer) byteBuffer);
    }
  }
we do not need to clean heapByteBuffer manually, so we just leave it alone.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/utils/MmapUtil.java