RFR: 8289822: G1: Make concurrent mark code owner of TAMSes [v2]

[Thomas Schatzl]

On Thu, 14 Mar 2024 10:15:53 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:
>> 
>>  - Merge branch 'master' into 8289822-concurrent-mark-tams-owner
>>  - Do the mark information reset more fine grained (like before this change) to not potentially make HeapRegion::hr_clear() too slow
>>  - Fixes
>>  - some attempts to not have TAMSes always be updated for all regions
>>  - Remove _top_at_mark_start HeapRegion member
>>  - 8326781
>>    
>>    initial version
>>    
>>    initial draft
>>    
>>    some improvmeents
>>    
>>    Make things work
>>    
>>    forgotten fix
>
> src/hotspot/share/gc/g1/g1ConcurrentMark.hpp line 543:
> 
>> 541:   // Top pointer for each region at the start of marking. Must be valid for all committed
>> 542:   // regions.
>> 543:   HeapWord* volatile* _top_at_mark_starts;
> 
> I wonder if one can use `HeapWord* volatile _top_at_mark_starts[];` to emphasize that it's an array.

No, it would be interpreted as flexible array, which would need to be the last member of the class.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18150#discussion_r1525112656