RFR(L): 8198691: CodeHeap State Analytics

Schmidt, Lutz lutz.schmidt at sap.com
Mon Mar 19 16:00:08 UTC 2018

Dear all, 

this is the next (second) iteration of my CodeHeap State Analytics effort. It reflects all the comments and suggestions I received on my initial RFR (sent out on March 1st). Please read on to learn what was changed and what kept as is.

May I please request reviews for 

Bug:    https://bugs.openjdk.java.net/browse/JDK-8198691
Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8198691.01/

Instead of keeping the long tail of comments and responses, I decided to provide a summary of what happened.
 - Most of the new code was moved to new files: share/code/codeHeapState.cpp and share/code/codeHeapState.hpp
 - I have added, as requested, an abbreviated version of the "General Description" chapter to codeHeapState.cpp
 - In case of SegmentedCodeCache, the iteration is limited to FOR_ALL_ALLOCABLE_HEAPS(). There were issues in aot tests when using FOR_ALL_HEAPS().
 - All references to the RFE id should be gone.
 - In share/runtime/java.cpp, the call to CompileBroker::print_heapinfo() now is close to "PrintCodeCache" for both, product and nonproduct cases.
 - The edited/updated documentation is available as an attachment to the bug (in PDF format).
 - I added code to share/code/codeCache.cpp (report_codemem_full()) to print the CodeHeap state for the first occurrence of the "full" condition.
 - The code style "hickups", noted by Tobias Hartmann, are gone.
 - The compile time warnings and errors are resolved.

-XX:+PrintCodeHeapState vs. -Xlog:codecache=Trace
I clearly understand and support the intention to get rid of the Print* command line arguments. Therefore, the PrintCodeHeapState command line argument is gone. You can request the CodeHeap state analytics with the -Xlog:codecache=Trace (vm shutdown) or -Xlog:codecache=Debug (CodeCache full and vm shutdown) switches. The output is directed to tty, not to the log stream. 

The reason for not using the log stream is simple: UL prefixes every line with a timestamp and the trace tags. Unfortunately, that messes up my formatting big time. The jcmd output, on the other hand, will not have the UL prefixes. I would have to distinguish between UL and jcmd output when formatting. In addition, I do not see a benefit from adding the same UL prefix to thousands of lines. 

Comments are very welcome! 

Best Regards,


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