RFR: Borrow from old gen

[Kelvin Nilsen]

On Mon, 7 Feb 2022 22:27:26 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.cpp line 120:
> 
>> 118:       // GCLABs are for evacuation so we must be in evacuation phase.  If this allocation is successful, increment
>> 119:       // the relevant evac_expended rather than used value.
>> 120:       allocating_gclab = true;
> 
> Do we really need a new parameter here? The information is carried in the type of the allocation request (`req`) which is also passed to `allocate_with_affiliation` (the request goes all the way down to `try_allocate_in`).

Thank you.  I will change this.

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