RFR: Borrow from old gen

[Kelvin Nilsen]

On Mon, 7 Feb 2022 22:30:04 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This commit represents multiple months of incremental performance improvements to allow generational shenandoah to run more efficiently, especially with larger heap sizes and high memory utilization.
>> 
>> Specific improvements are described in individual commit log messages.
>
> src/hotspot/share/gc/shenandoah/shenandoahFreeSet.hpp line 82:
> 
>> 80:   ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions);
>> 81: 
>> 82:   // How many regions dedicated to GC allocations (for evacuation or promotion) are currently free?
> 
> I agree with these comments - let's delete the question marks?

Fixed.

> src/hotspot/share/gc/shenandoah/shenandoahHeap.inline.hpp line 394:
> 
>> 392:                // the desired PLAB size and retry PLAB allocation to avoid cascading of shared memory allocations.
>> 393:                ShenandoahThreadLocalData::set_plab_size(thread, PLAB::min_size());
>> 394:                copy = allocate_from_gclab(thread, size);
> 
> Should this be `allocate_from_plab` as above?

Yes. Thank you for catching that.

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