RFR: 8270009: Factor out and shuffle methods in G1CollectedHeap::do_collection_pause_at_safepoint_helper

[Thomas Schatzl]

On Sun, 11 Jul 2021 22:06:46 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Hi all,
>> 
>>   can I get reviews for this change that factors out a few methods from `do_collection_pause_at_safepoint_helper` and reshuffles code from `gc_prologue`/`gc_epilogue` to be able to put those into parallel phase(s) later.
>> 
>> Testing: tier1-5
>> 
>> Thanks,
>>   Thomas
>
> src/hotspot/share/gc/g1/g1CollectedHeap.cpp line 3020:
> 
>> 3018:   ResourceMark rm;
>> 3019: 
>> 3020:   IsGCActiveMark active_gc_mark;
> 
> Moving the IsGCActiveMark here expands the scope of is_gc_active() being true to cover areas it didn't used to.  I _think_ this is okay, but I didn't check all callers carefully.

None of the code before that (verification, timing setup, heap printing) should be dependent on that. Actually I was considering moving the mark right after the guarantee in `G1CollectedHeap::do_collection_pause_at_safepoint`, but then I reconsidered due to the `GCLocker` check there.

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PR: https://git.openjdk.java.net/jdk/pull/4744