RFR: Add generations to freeset [v5]

[Kelvin Nilsen]

On Thu, 13 Apr 2023 02:16:43 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove debug instrumentation
>
> src/hotspot/share/gc/shenandoah/shenandoahFreeSet.hpp line 83:
> 
>> 81:   HeapWord* allocate_old_with_affiliation(ShenandoahAffiliation affiliation, ShenandoahAllocRequest& req, bool& in_new_region);
>> 82: 
>> 83:   // While holding the heap lock, allocate memory for a single object which is to be entirely contained
> 
> I see that the callers of `allocate_...()` assert that the heap is locked, but would it be a good idea to also have these `allocate_...()` methods do so as well? May be I am being paranoid.

I've added the asserts.  It's a good improvement.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/250#discussion_r1170634154