RFR: 8325807: Shenandoah: Refactor full gc in preparation for generational mode changes

[Y. Srinivas Ramakrishna]

On Fri, 16 Feb 2024 19:49:07 GMT, William Kemper <wkemper at openjdk.org> wrote:

> Changes to prepare for generational mode:
> * A `phase5_epilogue` method is added to run the final steps of the gc
> * Prepare for mark operation is run by multiple worker threads
> * `finish_region` method of compacting preparation closure is renamed to `finish`
> * The prepare for compaction loop is extracted to a template method, parameterized on closure type

src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp line 431:

> 429: 
> 430: template<typename ClosureType>
> 431: void ShenandoahPrepareForCompactionTask::prepare_for_compaction(ClosureType& cl,

See some related comments in sister PR:

- https://github.com/openjdk/shenandoah/pull/398/files#r1494913729
- https://github.com/openjdk/shenandoah/pull/398/files#r1494910380

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PR Review Comment: https://git.openjdk.org/jdk/pull/17894#discussion_r1494924914