RFR: Enforce max regions

[Kelvin Nilsen]

On Tue, 6 Dec 2022 22:18:01 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp line 1031:
>> 
>>> 1029:     // affiliation to OLD_GENERATION and adjust the generation-use tallies.  The remnant of memory
>>> 1030:     // in the last humongous region that is not spanned by obj is currently not used.
>>> 1031:     for (size_t i = index(); i < index_limit; i++) {
>> 
>> Do we need to worry about races here? Could we have a separate evacuating thread take a new, old region to use for PLABs _after_ we checked old available regions?
>
> Good catch. I need to grab the heap lock for part of this code.

Good catch.  I need to grab the heap lock for part of this work.

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PR: https://git.openjdk.org/shenandoah/pull/179