Integrated: 8339616: GenShen: Introduce new state to distinguish promote-in-place phase as distinct from concurrent evacuation

[William Kemper]

On Fri, 20 Sep 2024 21:04:50 GMT, William Kemper <wkemper at openjdk.org> wrote:

> The generational mode for Shenandoah is able to promote regions in place (effectively moving an entire region of live objects, without evacuating any objects). It does this during a normal evacuation phase. However, in some cases, Shenandoah may choose to skip the evacuation phase, _even when there are entire regions to promote_. Prior to this PR, Shenandoah would essentially force itself into an evacuation phase, with nothing to evacuate. Though this was expedient, it caused all manner of knock-on effects and unintended consequences with barriers and asserts and the state of the heap. Here, we have reverted that business and created a path for this special "only doing in place promotions" cycle that does not cause the heap to expect to evacuate objects or find forwarding pointers in them.

This pull request has now been integrated.

Changeset: fdd5ed99
Author:    William Kemper <wkemper at openjdk.org>
URL:       https://git.openjdk.org/shenandoah/commit/fdd5ed9906e1437e9ba4c0c6eeb4af3dd74b3adc
Stats:     211 lines in 14 files changed: 131 ins; 31 del; 49 mod

8339616: GenShen: Introduce new state to distinguish promote-in-place phase as distinct from concurrent evacuation

Reviewed-by: kdnilsen, shade, ysr

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PR: https://git.openjdk.org/shenandoah/pull/503