RFR: 8337511: Implement JEP 404: Generational Shenandoah (Experimental) [v11]

[Aleksey Shipilev]

On Tue, 26 Nov 2024 00:37:32 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This PR merges JEP 404, a generational mode for the Shenandoah garbage collector. The JEP can be viewed here: https://openjdk.org/jeps/404. We would like to target JDK24 with this PR.
>
> William Kemper has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'shenandoah/master' into great-genshen-pr-redux
>  - 8344985: GenShen: Refactor arraycopy barrier for generational mode
>    
>    Reviewed-by: shade

I checked all review threads, and I think my review feedback was appropriately addressed. I see no (new) test failures in my local testing as well.

Thank you all, this is a huge piece of engineering work, and it looks good for experimental feature. We would probably make a few touchups and simplifications after the integration. I hope this would stabilize in the future releases to become a new default mode for Shenandoah!

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Marked as reviewed by shade (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/21273#pullrequestreview-2460929110