RFR: Borrow from old gen [v2]

[Kelvin Nilsen]

On Tue, 8 Feb 2022 16:37:27 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Respond to reviewer feedback
>
> src/hotspot/share/gc/shenandoah/shenandoahCollectionSet.cpp line 93:
> 
>> 91:   if (ShenandoahHeap::heap()->mode()->is_generational()) {
>> 92:     if (ShenandoahHeap::heap()->is_aging_cycle()) {
>> 93:       r->decrement_age();
> 
> Why are we decreasing the age here? Putting the region in the collection set will call `make_cset` on the region which sets the age to zero.

Sorry.  Thanks for catching this.  This was my "compensation" that I had inserted when I was trying to increment all ages right after final mark.  When I backed out that change, I forgot to remove this.  Gone now.

> src/hotspot/share/gc/shenandoah/shenandoahCollectionSet.inline.hpp line 64:
> 
>> 62: }
>> 63: 
>> 64: #ifdef KELVIN_VERBOSE
> 
> Some instrumentation sneaked in here.

Thanks.  These two methods are now removed with refactoring to account for evacuation reserve inside the add_region() method.

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PR: https://git.openjdk.java.net/shenandoah/pull/110