RFR: 8343782: G1: Use one G1CardSet instance for multiple old gen regions [v3]

[Albert Mingkun Yang]

On Tue, 3 Dec 2024 19:56:54 GMT, Ivan Walulya <iwalulya at openjdk.org> wrote:

>> src/hotspot/share/gc/g1/g1CardSet.cpp line 788:
>> 
>>> 786:   G1HeapRegion* r = G1CollectedHeap::heap()->region_at(region_idx);
>>> 787:   assert(r->rem_set()->card_set() != this, "must be");
>>> 788: #endif
>> 
>> Since this introduces local vars, can they be grouped in a `{}` scope?
>
> It's possible, but I have not seen this done in the hotspot code.

With a quick search, I can find some in runtime code, though not universal. Regardless, it's better encapsulation, IMO.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22015#discussion_r1875612042