RFR: 8325516: Shenandoah: Move heap change tracking into ShenandoahHeap [v2]

[Y. Srinivas Ramakrishna]

On Thu, 8 Feb 2024 19:42:15 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Shenandoah sets a flag when new regions are allocated or retired. This flag currently resides in the control thread. Moving it into the heap reduces code duplication with upcoming generational mode changes.
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use try_set for updating heap changed flag

LGTM; good cleanup! Minor doc suggestion.

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp line 298:

> 296:   bool _gc_state_changed;
> 297:   ShenandoahSharedBitmap _gc_state;
> 298:   ShenandoahSharedFlag   _heap_changed;

The documentation at `has_changed()` is good, but may be a single small documentation comment here, perhaps something like:


   ShenandoahSharedFlag _heap_changed;  // set if heap has changed since last check


or may be more elaborate:

   // tracks if new regions have been allocated or retired since last check

-------------

Marked as reviewed by ysr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17777#pullrequestreview-1871273842
PR Review Comment: https://git.openjdk.org/jdk/pull/17777#discussion_r1483600601