JDK-8231460: Java update from 11.0.11 to 11.0.13 changes JVM code cache behavior and results in more process cpu usage and unexpected profiled nmethods memory usage

[Josef Lehner]

Dear OpenJDK team,

as described in this StackOverflow question, I want to reach out to you and
question whether the JVM code cache / codeheap still works as designed.
https://stackoverflow.com/questions/70086548/java-update-from-11-0-11-to-11-0-13-changes-jvm-code-cache-behavior-and-results

What we experience in our huge application is that with Java 11.0.13 and
-XX:ReservedCodeCacheSize=375m the code cache / codeheap 'profiled
nmethods' (C1 optimized, ~ 180 MB) drops after a very short time to a very
low level (less than 50 MB) and stays at this level forever while
'non-profiled nmethods' (C2 optimized) is already at its limits.
After we tripled the -XX:ReservedCodeCacheSize to 1024 MB, both areas
'profiled nmethods' and 'non-profiled nmethods' have stayed at a much
higher constant level (~ 258 MB) for over a week now instead of dropping to
less than 50 MB after 15 min (-XX:ReservedCodeCacheSize=375m) or dropping
after 3 hours (-XX:ReservedCodeCacheSize=512m).
>From my point of view as a non-expert I would expect that the C1 optimized
code does not get removed (or at least not so much) from 'profiled
nmethods' as there is no space left in 'non-profiled nmethods' to optimize
it further. What do you think?

Important changes in 11.0.12:
https://bugs.openjdk.java.net/browse/JDK-8223444 Improve CodeHeap Free
Space Management
https://bugs.openjdk.java.net/browse/JDK-8231460 Performance issue
(CodeHeap) with large free blocks

Best regards
Josef Lehner