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

[Tobias Hartmann]

Hi Josef,

Thanks for reporting this issue!

Any chance you could run your application with different builds to narrow the problem down to a
single change?

@Lutz: As the author of 8223444 and 8231460, any ideas?

Best regards,
Tobias


On 01.12.21 16:35, Josef Lehner wrote:
> 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
>