8354078: Shenandoah: Make the generational mode be non-experimental (implementation)

[earthling-amzn]

Testing:

% ./build/linux-x86_64-server-fastdebug/jdk/bin/java -XX:+UseShenandoahGC -XX:ShenandoahGCMode=generational --version
openjdk 25 2025-09-16
OpenJDK Runtime Environment (fastdebug build 25-make-genshen-non-experimental)
OpenJDK 64-Bit Server VM (fastdebug build 25-make-genshen-non-experimental, mixed mode)

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Change requires CSR request JDK-8354079 to be approved
• Commit message must refer to an issue

Issues

• JDK-8354078: Shenandoah: Make the generational mode be non-experimental (implementation) (Enhancement - P4)
• JDK-8354079: Shenandoah: Make the generational mode be non-experimental (CSR)

Reviewers

• Y. Srinivas Ramakrishna (@ysramakrishna - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/25270/head:pull/25270
$ git checkout pull/25270

Update a local copy of the PR:
$ git checkout pull/25270
$ git pull https://git.openjdk.org/jdk.git pull/25270/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 25270

View PR using the GUI difftool:
$ git pr show -t 25270

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/25270.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

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[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@earthling-amzn The following labels will be automatically applied to this pull request:

• hotspot-gc
• shenandoah

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[mlbridge]

Webrevs

• 00: Full (719126e6)

[ysramakrishna]

Break out the production bubbly! 🍾

Reviewed!

[ysramakrishna]

Just noticed that gc/shenandoah/options/TestModeUnlock.java needs to be taught that "generational" is no longer experimental. It's failing in the GHA tests.