8373714: Shenandoah: Register heuristic penalties following a degenerated GC

[kdnilsen]

Hi all,

This pull request contains a backport of commit 385c4f81 from the openjdk/jdk repository.

The commit being backported was authored by Kelvin Nilsen on 8 Jan 2026 and was reviewed by William Kemper.

Thanks!

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8373714 needs maintainer approval

Issue

• JDK-8373714: Shenandoah: Register heuristic penalties following a degenerated GC (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/162/head:pull/162
$ git checkout pull/162

Update a local copy of the PR:
$ git checkout pull/162
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/162/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 162

View PR using the GUI difftool:
$ git pr show -t 162

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/162.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back kdnilsen! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

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

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 01: Full - Incremental (70376cfd)
• 00: Full (dc67f4a7)

[shipilev]

So adding virtual in this hunk is what makes the backport unclean? Do you need to do it here?

[kdnilsen]

I can remove virtual and override from these declarations and the code still compiles on Linux with gcc 10.5.0.

My recollection is that certain other compilers (e.g. MacOS and/or Windows) are less forgiving, which is what motivated these changes in the original PR.

The GHA testing for backports is not as thorough as the GHA for changes to master.

[shipilev]

Yes, prefer clean backports.

I think you need to go to https://github.com/kdnilsen/jdk25u-dev/actions and enable GHA for your personal fork to get the GHA run.

[shipilev]

Once you enable GHA runs, you need to either trigger the run manually, or push a commit here.