RFR: 8299701: Remove unused GCCause::_wb_conc_mark

[Erik Österlund]

On Mon, 9 Jan 2023 14:50:50 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

>> Please review this change to remove GCCause::_wb_conc_mark and the supporting
>> implementation.  After JDK-8293824 it is no longer used as the cause when
>> requesting a GC.
>> 
>> Note: The implementation in ZGC appears to have never been used.  Prior to
>> JDK-8293824 this cause was only used by a G1-specific WB function.  (In the
>> deep mists of time it might have also been used to trigger a CMS concurrent
>> cycle; I didn't bother looking into that.)
>> 
>> Testing:
>> mach5 tier1
>
> src/hotspot/share/gc/g1/g1CollectedHeap.hpp line 256:
> 
>> 254:   // (c) cause == _dcmd_gc_run and +ExplicitGCInvokesConcurrent,
>> 255:   // (d) cause == _wb_breakpoint,
>> 256:   // (e) cause == _g1_periodic_collection and +G1PeriodicGCInvokesConcurrent.
> 
> I suppose (e) should be (d) now.

...never mind my nit, it looks right already.

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PR: https://git.openjdk.org/jdk/pull/11893