RFR: 8306833: Change CardTable::_covered to static array [v2]

[Albert Mingkun Yang]

On Tue, 25 Apr 2023 14:02:28 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:
>> 
>>  - protected-destructor
>>  - card-table-array-field
>
> src/hotspot/share/gc/g1/g1BarrierSet.hpp line 52:
> 
>> 50:   void invalidate(JavaThread* thread, MemRegion mr);
>> 51: 
>> 52:   ~G1BarrierSet() = default;
> 
> Why is this being privatized?

To minimize the public API; it doesn't need to be public.

> src/hotspot/share/gc/shared/cardTable.hpp line 60:
> 
>> 58: 
>> 59:   // The covered regions should be in address order.
>> 60:   MemRegion _covered[max_covered_regions];
> 
> The whole concept of covered_regions doesn't seem to belong in this class.  G1CardTable derives from
> CardTable, but doesn't appear to use this at all.

`_covered` is not really used by G1, so are some other fields, e.g. `_guard_region`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13636#discussion_r1176643608
PR Review Comment: https://git.openjdk.org/jdk/pull/13636#discussion_r1176647288