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

[Leo Korinth]

On 18/10/2019 17:45, Igor Ignatyev wrote:
> Hi Leo,
> 
> there are still some tests which can be cleaned up, e.g. test/hotspot/jtreg/vmTestbase/metaspace/gc/watermark_10_20/TestDescription.java has '@requires vm.gc != "ConcMarkSweep"'. it also makes sense to remove 'vm.gc.ConcMarkSweep' from requires.properties in TEST.ROOT files.
> 
> -- Igor

Thanks! I have cleaned up four occurrences '@requires vm.gc != 
"ConcMarkSweep"' as well as removed vm.gc.ConcMarkSweep from TEST.ROOT.

/Leo
> 
>> On Oct 18, 2019, at 1:20 AM, Leo Korinth <leo.korinth at oracle.com> 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
>