RFR: Add generations to freeset [v8]

[Kelvin Nilsen]

On Thu, 20 Apr 2023 16:24:27 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 207 commits:
>> 
>>  - Merge remote-tracking branch 'origin' into add-generations-to-freeset
>>  - Respond to reviewer feedback
>>    
>>    Various improvements suggested by reviewers.  Mostly improved comments
>>    and some minor refactoring.
>>  - Add TODO comment for exapnsion of old-gen
>>  - Remove debug instrumentation
>>  - Merge master
>>  - Fix calculation of minimum fill size
>>    
>>    We were incorrectly using byte size rather than word size.
>>  - Fix error in ShenandoahFreeSet usage accounting
>>    
>>    We were incorrectly increasing used for plab padding.  That is
>>    old_collector memory and should not affect mutator usage.  This commit
>>    also includes some refactoring, additional assertions, and additional
>>    verification of consistent free-space accounting.
>>  - Fix typo in a comment
>>  - Fix white space
>>  - Merge remote-tracking branch 'GitFarmBranch/add-generations-to-freeset' into add-generations-to-freeset
>>  - ... and 197 more: https://git.openjdk.org/shenandoah/compare/016bf071...7319eeeb
>
> src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp line 534:
> 
>> 532:         _heap->notify_mutator_alloc_words(waste >> LogHeapWordSize, true);
>> 533:       }
>> 534:       assert(probe_mutator_set(idx), "Must be mutator free: " SIZE_FORMAT, idx);
> 
> Looking at the assertions in `in_mutator_set()`, could you explain which of those wouldn't hold if you used `in_mutator_set()` in this assert, rather than `probe_mutator_set()`?

There is a comment that describes the difference in the description of the probe_ membership functions.  Is this sufficient?

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/250#discussion_r1174061319