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

[Igor Ignatyev]

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

> 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