RFR: 8329603: G1: Merge G1BlockOffsetTablePart into G1BlockOffsetTable [v3]

[Ivan Walulya]

On Fri, 5 Apr 2024 10:05:37 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> Hi all,
>> 
>> This patch merges `G1BlockOffsetTablePart` into `G1BlockOffsetTable`. The previous fields `_reserved` and `_offset_base` of `G1BlockOffsetTable` are marked as `static` so that they can be shared by BOTs of all the heap regions.
>> 
>> The tests `make test-tier1_gc` passed locally. Thanks for taking the time to review.
>> 
>> Best Regards,
>> -- Guoxiong
>
> Guoxiong Li has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Remove unnecessary comments.
>  - Fix indentation issue.

Changes requested by iwalulya (Reviewer).

src/hotspot/share/gc/g1/g1HeapRegion.hpp line 77:

> 75:   HeapWord* volatile _top;
> 76: 
> 77:   G1BlockOffsetTable* _bot;

I suppose there is no longer a reason for this to be part of the region. Any downside to referring to it using `g1h->bot()`?

src/hotspot/share/gc/g1/g1HeapRegion.inline.hpp line 107:

> 105: }
> 106: 
> 107: inline HeapWord* HeapRegion::block_start(const void* addr, HeapWord* const pb) const {

Can we move the assert `assert(addr >= _hr->bottom() && addr < _hr->top(), "invalid address");` here?

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PR Review: https://git.openjdk.org/jdk/pull/18634#pullrequestreview-1986757217
PR Review Comment: https://git.openjdk.org/jdk/pull/18634#discussion_r1556042441
PR Review Comment: https://git.openjdk.org/jdk/pull/18634#discussion_r1556022980