RFR: 8232365: Implementation for JEP 363: Remove the Concurrent Mark Sweep (CMS) Garbage Collector

[Leo Korinth]

On 18/10/2019 15:50, Aleksei Voitylov wrote:
> Leo,
> 
> your changes build fine on aarch64, arm and ppc. This is not a full review.
> 
> -Aleksei

Good, thanks for testing!

/Leo
> 
> On 18/10/2019 11:20, Leo Korinth wrote:
>> Hi,
>>
>> Here is a patch that removes the CMS GC.
>>
>> I have neither tested arm nor ppc; I hope my changes to those .ad 
>> files are correct, if someone can test those architectures, that would 
>> be great.
>>
>> Please take an extra look at 
>> CollectedHeap::check_for_non_bad_heap_word_value, it was buggy before 
>> (but never called), It is now called (and hopefully correct).
>>
>> I have tried to remove most parts of CMS. I have not made it a goal to 
>> remove all traces of CMS. I guess there are much more to cleanup, and 
>> suggestions of more to remove are welcomed. I think more complicated 
>> cleanups should be dealt with in separate enhancements.
>>
>> Not fully addressed in code, but an issue that has to be dealt with, 
>> how do I obsolete -Xconcgc and -Xnoconcgc? I believe the option should 
>> be obsoleted, though I do not know if we have any precedence 
>> obsoleting -X options.
>>
>> My patch prints:
>>
>> $ java -Xconcgc -jar Notepad.jar
>> Java HotSpot(TM) 64-Bit Server VM warning: -Xconcgc uses 
>> UseConcMarkSweepGC
>>
>> I guess that is not enough for being obsolete, compare with:
>>
>> $ java -XX:UseConcMarkSweepGC -jar Notepad.jar
>> Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option 
>> UseConcMarkSweepGC; support was removed in 14.0
>>
>> Bug:
>>   https://bugs.openjdk.java.net/browse/JDK-8232365
>>
>> Webrev:
>>   http://cr.openjdk.java.net/~lkorinth/8232365/00
>>
>> Testing:
>>   tier 1-5.
>>
>> Thanks,
>> Leo