RFR: 8361099: Shenandoah: Improve heap lock contention by using CAS for memory allocation [v20]

[Xiaolong Peng]

On Tue, 6 Jan 2026 01:21:21 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> Xiaolong Peng has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 265 commits:
>> 
>>  - Merge branch 'openjdk:master' into cas-alloc-1
>>  - Fix build error after merging from tip
>>  - Merge branch 'master' into cas-alloc-1
>>  - Merge branch 'master' into cas-alloc-1
>>  - Some comments updates as suggested in PR review
>>  - Fix build failure after merge
>>  - Expend promoted from ShenandoahOldCollectorAllocator
>>  - Merge branch 'master' into cas-alloc-1
>>  - Address PR comments
>>  - Merge branch 'openjdk:master' into cas-alloc-1
>>  - ... and 255 more: https://git.openjdk.org/jdk/compare/de81d389...cf13b7b5
>
> src/hotspot/share/gc/shenandoah/shenandoahAllocator.hpp line 79:
> 
>> 77:   int refresh_alloc_regions(ShenandoahAllocRequest* req = nullptr, bool* in_new_region = nullptr, HeapWord** obj = nullptr);
>> 78: #ifdef ASSERT
>> 79:   virtual void verify(ShenandoahAllocRequest& req) { }
> 
> Need a comment to explain what verify does.  Is this simply checking to make sure the req is "properly formatted"?  I think the intention is to enforce that req affiliation corresponds to ALLOC_PARTITION.  Would be good to clarify this in the comment.
> 
> Do we need this to be virtual?  It seems like a single templated implementation would suffice.

Yes, it can be templated implementation, I'll update the implementation to use template.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26171#discussion_r2673695164