Lucee 6: Free Perm Gen Space is less than 5% free

I recently updated Lucee from version to version and in the logs I find many warnings like this:

Free Perm Gen Space is less than 5% free: shrinking all template classloaders : consider increasing allocated Perm Gen Space

Here’s the information about Lucee/Java:

Servlet Container: Apache Tomcat/9.0.62
Java: (IBM Corporation) 64bit
OS: Linux (4.15.0-213-generic) 64bit
Architecture: 64bit
CATALINA_OPTS: -Xms2048m -Xmx32768m -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:+ExitOnOutOfMemoryError

Apparently there is no slowdown in the application but I’m worried.
What could cause this waning?


update: I changed the JDK from openJ9 to hotspot and the warnings went away.

How do you do this? What is the benefit of doing? What JDK is the official recommendation?