RFR: 8331609: GenShen: Refactor generational mode allocations [v4]

[William Kemper]

On Tue, 7 May 2024 21:13:54 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp line 1129:
>> 
>>> 1127:   if (result != nullptr && req.is_old()) {
>>> 1128:     old_generation()->configure_plab_for_current_thread(req);
>>> 1129:     // TODO: Is this only necessary for 'shared' allocations?
>> 
>> I believe this is only necessary for shared allocs.  I'm supportive of making this change as part of PR, though it might be safer to do in separate PR.
>> 
>> (If this is a PLAB allocation, the objects allocated within the PLAB will be independently registered when they are allocated.)
>
> I'm going to test making this change as part of this PR.

Pipelines look okay with only registering shared objects here.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/427#discussion_r1595688231