8329223: Parallel: Parallel GC resizes heap even if -Xms = -Xmx

[benty-amzn]

Clean backport of a low-risk change to address unexpected behavior with Parallel GC when Xms == Xmx
Passes local tier-1 testing on linux x86_64

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8329223 needs maintainer approval

Issue

• JDK-8329223: Parallel: Parallel GC resizes heap even if -Xms = -Xmx (Bug - P3 - Approved)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/587/head:pull/587
$ git checkout pull/587

Update a local copy of the PR:
$ git checkout pull/587
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/587/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 587

View PR using the GUI difftool:
$ git pr show -t 587

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/587.diff

Webrev

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[bridgekeeper]

👋 Welcome back btaylor! 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]

@benty-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:

8329223: Parallel: Parallel GC resizes heap even if -Xms = -Xmx

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 4 new commits pushed to the master branch:

• acff39d: 8319338: tools/jpackage/share/RuntimeImageTest.java fails with -XX:+UseZGC
• a1e0c5d: 8332253: Linux arm32 build fails after 8292591
• 8ff8163: 8331466: Problemlist serviceability/dcmd/gc/RunFinalizationTest.java on generic-all
• c44d4e9: 8321107: Add more test cases for JDK-8319372

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[openjdk]

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

[openjdk]

⚠️ @benty-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.

[mlbridge]

Webrevs

• 00: Full (7a1411f8)

[RealCLanger]

@benty-amzn the approval request is still missing.

[benty-amzn]

/approval request Clean backport of a low-risk change to address unexpected behavior with Parallel GC when Xms == Xmx.

[openjdk]

@benty-amzn
8329223: The approval request has been created successfully.

[benty-amzn]

/integrate

[openjdk]

Going to push as commit 4b1d95c.
Since your change was applied there have been 11 commits pushed to the master branch:

• d986096: 8330464: hserr generic events - add entry for the before_exit calls
• 20da646: 8329605: hs errfile generic events - move memory protections and nmethod flushes to separate sections
• 9035981: 8321812: Update GC tests to use execute[Limited]TestJava
• a4d2a5a: 8312194: test/hotspot/jtreg/applications/ctw/modules/jdk_crypto_ec.java cannot handle empty modules
• 201e663: 8320681: [macos] Test tools/jpackage/macosx/MacAppStoreJlinkOptionsTest.java timed out on macOS
• fe4a2ae: 8329109: Threads::print_on() tries to print CPU time for terminated GC threads
• cdfe2f4: 8329840: Fix ZPhysicalMemorySegment::_end type
• acff39d: 8319338: tools/jpackage/share/RuntimeImageTest.java fails with -XX:+UseZGC
• a1e0c5d: 8332253: Linux arm32 build fails after 8292591
• 8ff8163: 8331466: Problemlist serviceability/dcmd/gc/RunFinalizationTest.java on generic-all
• ... and 1 more: https://git.openjdk.org/jdk21u-dev/compare/ff295b7fc417d4ce690d70015a1633ded67eceaa...master

Your commit was automatically rebased without conflicts.

[openjdk]

@benty-amzn Pushed as commit 4b1d95c.

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