8365956: GenShen: Adaptive tenuring threshold algorithm may raise threshold prematurely

[earthling-amzn]

Not clean, but not especially difficult to resolve.

---

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-8365956 needs maintainer approval

Issue

• JDK-8365956: GenShen: Adaptive tenuring threshold algorithm may raise threshold prematurely (Enhancement - P4 - Approved)

Reviewers

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

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u.git pull/198/head:pull/198
$ git checkout pull/198

Update a local copy of the PR:
$ git checkout pull/198
$ git pull https://git.openjdk.org/jdk25u.git pull/198/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 198

View PR using the GUI difftool:
$ git pr show -t 198

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk25u/pull/198.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]

@earthling-amzn This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8365956: GenShen: Adaptive tenuring threshold algorithm may raise threshold prematurely

Reviewed-by: phh, kdnilsen

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 73 new commits pushed to the master branch:

• a3854cf: 8368698: runtime/cds/appcds/aotCache/OldClassSupport.java assert(can_add()) failed: Cannot add TrainingData objects
• f5c2756: 8362204: test/jdk/sun/awt/font/TestDevTransform.java fails on Ubuntu 24.04
• ee6a040: 8365265: x86 short forward jump exceeds 8-bit offset in methodHandles_x86.cpp when using Intel APX
• ... and 70 more: https://git.openjdk.org/jdk25u/compare/b105b7b5d6dd85ab3f1f8e6185848239dbf18521...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@phohensee) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[openjdk]

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

[mlbridge]

Webrevs

• 00: Full (afe8c511)

[phohensee]

I didn't see any obvious conflicts. It's worth calling out what they are, the maintainers will want to know to help estimate risk. You'll need a risk evaluation.

[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 a subtle off-by-one error when Shenandoah's generational mode computes a new tenuring threshold. In some cases, this may result in the tenuring threshold being raised prematurely. This results in an accumulation of objects in the young generation that should have been tenured. This in turn erodes the benefits of the generational mode and causes unpredictable cycle times when the tenuring threshold is lowered and all of these objects are tenured. We have tested this fix in all jtreg tiers and various performance benchmarks. This change only affects the generational mode for Shenandoah.

[openjdk]

@earthling-amzn
8365956: The approval request has been created successfully.

[earthling-amzn]

/integrate

[openjdk]

@earthling-amzn
Your change (at version afe8c51) is now ready to be sponsored by a Committer.

[shipilev]

/sponsor

[openjdk]

Going to push as commit c66d45a.
Since your change was applied there have been 74 commits pushed to the master branch:

• 66de4b4: 8368732: RISC-V: Detect support for misaligned vector access via hwprobe
• a3854cf: 8368698: runtime/cds/appcds/aotCache/OldClassSupport.java assert(can_add()) failed: Cannot add TrainingData objects
• f5c2756: 8362204: test/jdk/sun/awt/font/TestDevTransform.java fails on Ubuntu 24.04
• ... and 71 more: https://git.openjdk.org/jdk25u/compare/b105b7b5d6dd85ab3f1f8e6185848239dbf18521...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev @earthling-amzn Pushed as commit c66d45a.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.