RFR: 8328112: Remove CardTable::_guard_region [v2]

[Guoxiong Li]

On Fri, 15 Mar 2024 13:27:34 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Remove guard card.
>
> src/hotspot/share/gc/shared/cardTable.cpp line 82:
> 
>> 80: 
>> 81:   // each card takes 1 byte; + 1 for the guard card
>> 82:   size_t num_bytes = num_cards + 1;
> 
> I think it's better not to remove the `num_bytes` var. Otherwise, one have keep `one card == one byte` in mind everywhere #bytes is expected but #cards is used.

Do you want to leave `size_t num_bytes = num_cards;`? May it be strange? We already have the comment to clarify it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18324#discussion_r1526300767