RFR: 8326957: Implement JEP 474: ZGC: Generational Mode by Default [v5]

[Stefan Karlsson]

On Mon, 6 May 2024 07:23:14 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> This is the implementation task for `JEP 474: ZGC: Generational Mode by Default`. See the JEP for details. [JDK-8326667](https://bugs.openjdk.org/browse/JDK-8326667)
>
> Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Default to non generational ZGC with JVMCI

This is my proposal:

For this JEP, I propose that we stick with the current plan that -XX:+UseZGC always mean Generational ZGC. If the user try to enable the Graal JIT when running Generational ZGC, we'll print a warning and switch over to C2, just like we're doing today.

Then, as a follow-up, we can figure out what the correct behavior should be if the user specifies an incompatible GC and compiler combination.

@tkrodriguez Is this an OK action plan for you?

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PR Comment: https://git.openjdk.org/jdk/pull/18393#issuecomment-2107412501