8316319: Generational ZGC: The SoftMaxHeapSize might be wrong when CDS decreases the MaxHeapSize

[stefank]

Generational ZGC sets SoftMaxHeapSize to 90% of the MaxHeapSize if the user has not specified the maximum heap size with any of the available flags. Unfortunately, this break when CDS later on decreases the MaxHeapSize.

I propose that we solve this by moving the code that sets the SoftMaxHeapSize to the point after CDS and the GC has done its final tweaks to the MaxHeapSize.

This can be easily reproduced just by running:
java -XX:+UseZGC -XX:+ZGenerational -Xshare:dump -Xlog:gc+init -version

This wasn't caught in testing because our test infrastructure uses MaxRamPercentage to set the maximum heap size. I've manually verified that the patch fixes the issue and that SoftMaxHeapSize is set as expected.

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Issue

• JDK-8316319: Generational ZGC: The SoftMaxHeapSize might be wrong when CDS decreases the MaxHeapSize (Bug - P3)

Reviewers

• Axel Boldt-Christmas (@xmas92 - Reviewer)
• Sergey Bylokhov (@mrserb - Reviewer)

Reviewing

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[bridgekeeper]

👋 Welcome back stefank! 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]

@stefank The following label will be automatically applied to this pull request:

• hotspot-gc

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[stefank]

@mrserb - thanks for reporting this bug! Do you want to test this patch in your test infra?

[mlbridge]

Webrevs

• 00: Full (d41c5d25)

[xmas92]

lgtm.

[openjdk]

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

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

8316319: Generational ZGC: The SoftMaxHeapSize might be wrong when CDS decreases the MaxHeapSize

Reviewed-by: aboldtch, serb

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At the time when this comment was updated there had been 36 new commits pushed to the master branch:

• 015f6f5: 8315771: [JVMCI] Resolution of bootstrap methods with int[] static arguments
• 83b01cf: 8311922: [macOS] right-Option key fails to generate release event
• 542b300: 8315954: getArgumentValues002.java fails on Graal
• 0637900: 8316433: net.dll should delay load winhttp.dll
• 90bcdbd: 8316581: Improve performance of Symbol::print_value_on()
• 8350268: 8316453: [JVMCI] Using Xcomp on jargraal must eagerly initialize JVMCI
• 3809d69: 8316240: Open source several add/remove MenuBar manual tests
• 38bf119: 8310228: Improve error reporting for uncaught native exceptions on Windows
• 349723c: 8315739: Missing null check in os::vm_min_address
• 8cbe42b: 8316421: libjava should load shell32.dll eagerly
• ... and 26 more: https://git.openjdk.org/jdk/compare/e1870d360e05c372e672b519d7de2a60c333675b...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.

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[mrserb]

Looking into the patch.

[stefank]

Thanks for reviewing!
/integrate

[openjdk]

Going to push as commit fe86263.
Since your change was applied there have been 47 commits pushed to the master branch:

• 775e22a: 8316699: TestDynamicConstant.java fails with release VMs
• a1e0346: 8316698: build failure caused by JDK-8316456
• c72f004: 8316456: StackWalker may skip Continuation::yield0 frame mistakenly
• 041510d: 8315486: vmTestbase/nsk/jdwp/ThreadReference/ForceEarlyReturn/forceEarlyReturn002/forceEarlyReturn002.java timed out
• ef49e6c: 8316629: j.text.DateFormatSymbols setZoneStrings() exception is unhelpful
• 496264c: 8316435: sun.util.calendar.CalendarSystem subclassing should be restricted
• 1100dbc: 8316695: ProblemList serviceability/jvmti/RedefineClasses/RedefineLeakThrowable.java
• d3e8218: 8316306: Open source and convert manual Swing test
• 4e57177: 8316383: NullPointerException in AbstractSAXParser after JDK-8306632
• 3b397c8: 8315965: Open source various AWT applet tests
• ... and 37 more: https://git.openjdk.org/jdk/compare/e1870d360e05c372e672b519d7de2a60c333675b...master

Your commit was automatically rebased without conflicts.

[openjdk]

@stefank Pushed as commit fe86263.

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