RFR(L): 8198691: CodeHeap State Analytics

[Tobias Hartmann]

Hi Lutz,

first of all, this is a very nice enhancement!

I haven't looked at the code in detail yet (will wait for the next webrev). Here are some comments:
- The documentation is great and should at least go into the release notes (I've added the
release-not=yes label). I think we should also add something to the Tools Reference Guide [1] or
even the JVM Guide [2].
- As Robbin already pointed out, please use unified logging instead of PrintCodeHeapState. I think
that would also allow to specify <function> and <granularity> on the command line.
- I think it would be nice to print some/all of this new information if the code cache is full at
CodeCache::report_codemem_full() if PrintCodeHeapState is enabled. We had several customer reported
issues in the past where the compilers were disabled although there still was some free space in the
code cache. We were never able to reproduce/analyze but always expected this to be due to high
fragmentation.
- JFR integration would be nice but that should be done in a separate RFE
- It's a style question but I would prefer the pointer asterisk at the type not the argument. For
example, "outputStream* out" instead of "outputStream *out"
- heap.hpp: please put the commas after the definitions in the enum

Thanks,
Tobias

[1] https://docs.oracle.com/javase/9/tools/java.htm#JSWOR624
[2]
https://docs.oracle.com/javase/9/vm/java-virtual-machine-technology-overview.htm#JSJVM-GUID-982B244A-9B01-479A-8651-CB6475019281


On 01.03.2018 18:17, Schmidt, Lutz wrote:
> Dear all,
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> may I please request reviews for this quite voluminous enhancement:
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> Bug:     https://bugs.openjdk.java.net/browse/JDK-8198691
> 
> Webrev:  http://cr.openjdk.java.net/~lucy/webrevs/8198691.00/index.html  
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> Don’t get afraid! Most of the logic is new and isolated in a big, separate block in heap.cpp. The
> changes to other files are not difficult to understand.
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> If you need information about what this enhancement does and how it can be used, please refer to the
> bug description. There I have attached some documentation which will greatly help with understanding
> the code.
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> Thank you!
> 
> Lutz
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