8368152: Shenandoah: Incorrect behavior at end of degenerated cycle

[earthling-amzn]

Not clean, but conflict was trivial to resolve.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• JDK-8368152 needs maintainer approval
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8368152: Shenandoah: Incorrect behavior at end of degenerated cycle (Bug - P4 - Requested)

Reviewers

• Kelvin Nilsen (@kdnilsen - no project role)
• Paul Hohensee (@phohensee - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u.git pull/241/head:pull/241
$ git checkout pull/241

Update a local copy of the PR:
$ git checkout pull/241
$ git pull https://git.openjdk.org/jdk25u.git pull/241/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 241

View PR using the GUI difftool:
$ git pr show -t 241

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u/pull/241.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back wkemper! 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

• 00: Full (ed32b37a)

[phohensee]

Resolution in degen_event_message() looks ok.

[openjdk]

⚠️ @earthling-amzn This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[earthling-amzn]

/approval request This change fixes an error that causes the generational mode for Shenandoah to run back-to-back degenerated and full GCs without raising an out-of-memory error as expected. More importantly, it fixes an error that causes other Shenandoah modes to run a full gc unconditionally after every degenerated cycle (making a bad situation worse). We have tested this fix on jtreg tiers 1-3 and on various benchmarks: dacapo, specjvm, specjbb, extremem, and renaissance.

[openjdk]

@earthling-amzn
8368152: The approval request has been created successfully.