hivemq-community-edition: Why the memory usage is too large and the limit does not work？

Expected behavior

Memory is limited, memory usage is not that large

Actual behavior

As shown in the figure below, the memory consumption is too large and is increasing all the time. In fact, I only have a small number of clients sending data in groups every five minutes! The specific startup parameters are as follows：

-Xmx1536m -XX:MaxDirectMemorySize=1g

I checked the data directory, and the disk space is as follows.

In addition, I used JProfiler to check the memory usage, as shown below： Heap Non-Heap

To Reproduce

Steps

Add the following configuration to the startup parameters ‘-Xmx1536m -XX:MaxDirectMemorySize=1g’ .But it still takes up nearly 5g of memory

Reproducer code

Details

• Affected HiveMQ CE version(s): 2021.1
• Used JVM version: java11