RFR: 8306541: Refactor collection set candidate handling to prepare for JDK-8140326 [v12]

[Albert Mingkun Yang]

On Fri, 12 May 2023 11:09:00 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   please review this refactoring of collection set candidate set handling.
>> 
>> The idea is to improve the interface to collection set candidates and prepare for having collection set candidates available at any time to evacuate them at any young collection.
>> 
>> These preparations to allow for multiple sources for these candidates (from the marking, as now, and from retained regions, i.e. evacuation failed regions as per [JDK-8140326](https://bugs.openjdk.org/browse/JDK-8140326)).
>> 
>> This patch only uses candidates from marking at this time.
>>  
>> Also moves gc efficiency out of HeapRegion and associate it to the list element as it's not used otherwise.
>>     
>> In detail:
>>     * the collection set candidates set is not temporarily allocated any more, but the candidate collection set object is available all the time.
>>     
>>     * G1CollectionSetCandidates is the main class, representing the current candidates. Contains the "from marking" candidate list only (at this point).
>>     
>>     * there are several additional helper sets/lists
>>       * G1CollectionSetRegionList: list of HeapRegion*, typically sorted by efficiency (but not necessarily). Also does not contain gc efficiences.
>>       * G1CollectionCandidateList: list of candidates, i.e. HeapRegion* with their gc efficiency. Building block for the actual collection set candidates list.
>>     
>> All these sets implement C++ iterators for simpler use in various places.
>>     
>> Testing:
>>  - this patch only: tier1-3, gha
>>  - with JDK-8140326 tier1-7 (or 8?)
>> 
>> Thanks,
>>   Thomas
>
> Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 23 commits:
> 
>  - G1CollectionCandidateList -> G1CollectionCandidateRegionList attempt
>  - ayang review, make initial_old_regions an integer
>  - ayang review
>  - Merge branch 'master' into 8306541-refactor-cset-candidates
>  - Removed assert that is useless for now
>  - remove _reclaimable_bytes
>  - make reclaimable-bytes debug only
>  - ayang review (1)
>  - iwalulya review, naming compare fn
>  - iwalulya review
>  - ... and 13 more: https://git.openjdk.org/jdk/compare/3b430b9f...eb797c18

Marked as reviewed by ayang (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/13666#pullrequestreview-1424486427