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

[Martin Doerr]

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

Thanks! I've run another round of tests on all our platforms and the only failure I have seen is [JDK-8344312](https://bugs.openjdk.org/browse/JDK-8344312). I can do more stress testing by making GenShen the default GC. But that can still be done after integration.
Could you please add the failing test to the problem list to avoid failures in our CI?
gc/shenandoah/oom/TestAllocOutOfMemory.java 8344312 linux-ppc64le

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PR Comment: https://git.openjdk.org/jdk/pull/21273#issuecomment-2503393423