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8322279: Generational ZGC: Use ZFragmentationLimit and ZYoungCompactionLimit as percentage instead of multiples #173

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@mmyxym mmyxym commented Jan 16, 2024

This commit fixed incorrect use of production options of generational ZGC. Since JDK21 is the only LST version with generational ZGC, we need to fix the potential bugs.
Additional testing on fastdebug against test/hotspot/jtreg/gc/z


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  • JDK-8322279 needs maintainer approval

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  • JDK-8322279: Generational ZGC: Use ZFragmentationLimit and ZYoungCompactionLimit as percentage instead of multiples (Bug - P2 - Approved)

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bridgekeeper bot commented Jan 16, 2024

👋 Welcome back lmao! 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 openjdk bot changed the title Backport bf813be0f30391c67de3ea74c7522d7cbb8d3c3b 8322279: Generational ZGC: Use ZFragmentationLimit and ZYoungCompactionLimit as percentage instead of multiples Jan 16, 2024
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openjdk bot commented Jan 16, 2024

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

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openjdk bot commented Jan 16, 2024

⚠️ @mmyxym 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.

@openjdk openjdk bot added the rfr Pull request is ready for review label Jan 16, 2024
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mmyxym commented Jan 16, 2024

/approval We need to fix the quality issue of generational ZGC in jdk21.

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@mmyxym usage: /approval [<id>] (request|cancel) [<text>]

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mmyxym commented Jan 16, 2024

/approval request We need to fix the quality issue of generational ZGC in jdk21.

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8322279: The approval request has been created successfully.

@openjdk openjdk bot added the approval label Jan 16, 2024
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GoeLin commented Jan 16, 2024

Hi @mmyxym,
please give a risk estimate. What will be the effects of this this change? It looks as if a heurisitc will be changed by a factor of 100.
Will normal ZGC be affected? Any other GC? Will pause time, heap size etc be affected?

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mmyxym commented Jan 16, 2024

Hi @mmyxym, please give a risk estimate. What will be the effects of this this change? It looks as if a heurisitc will be changed by a factor of 100. Will normal ZGC be affected? Any other GC? Will pause time, heap size etc be affected?

Hi, I think the risk is quite low because the genz author @fisk treated it as a trivial fix and the actual behaviors changed by the commit is not critical that it only affects the decision of per cpu shared small page and aging heuristics. The change will make the policy decision more reasonable. The commit doesn't affect the behavior of normal ZGC or other GCS and won't affect those major metrics like pause time or heap size, etc.

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GoeLin commented Jan 18, 2024

The risk estimate should go into the fix request comment.

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mmyxym commented Jan 18, 2024

/approval request JDK21 is the only LST version with generational ZGC, we need to fix the potential bugs. The risk is quite low because the genz author @fisk treated it as a trivial fix and the actual behaviors changed by the commit is not critical that it only affects the decision of per cpu shared small page and aging heuristics. The change will make the policy decision more reasonable. The commit doesn't affect the behavior of normal ZGC or other GCS and won't affect those major metrics like pause time or heap size, etc.

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8322279: The approval request has been updated successfully.

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Looks good.

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openjdk bot commented Jan 19, 2024

@mmyxym 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:

8322279: Generational ZGC: Use ZFragmentationLimit and ZYoungCompactionLimit as percentage instead of multiples

Reviewed-by: eosterlund

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 77 new commits pushed to the master branch:

  • 6443937: 8323008: filter out harmful -std* flags added by autoconf from CXX
  • c8f0418: 8310031: Parallel: Implement better work distribution for large object arrays in old gen
  • 0d30c8d: 8318590: JButton ignores margin when painting HTML text
  • 8413dc0: 8312136: Modify runtime/ErrorHandling/TestDwarf.java to split dwarf and decoder testing
  • c79c5ef: 8315241: (fs) Move toRealPath tests in java/nio/file/Path/Misc.java to separate JUnit 5 test
  • 7eea17b: 8311663: Additional refactoring of Locale tests to JUnit
  • 419e016: 8322098: os::Linux::print_system_memory_info enhance the THP output with /sys/kernel/mm/transparent_hugepage/hpage_pmd_size
  • 309a16e: 8323659: LinkedTransferQueue add and put methods call overridable offer
  • e3084fc: 8304020: Speed up test/jdk/java/util/zip/ZipFile/TestTooManyEntries.java and clarify its purpose
  • 0668efa: 8317522: Test logic for BODY_CF in AbstractThrowingSubscribers.java is wrong
  • ... and 67 more: https://git.openjdk.org/jdk21u-dev/compare/cd166703a20c4ac51bc6478e8a0bb1275d9cb913...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 (@fisk) 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 openjdk bot added ready Pull request is ready to be integrated and removed approval labels Jan 19, 2024
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mmyxym commented Jan 19, 2024

/integrate

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openjdk bot commented Jan 19, 2024

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Your change (at version f2b5b3b) is now ready to be sponsored by a Committer.

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mmyxym commented Jan 19, 2024

Could committers please help to sponsor, thanks!

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fisk commented Jan 19, 2024

/sponsor

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openjdk bot commented Jan 19, 2024

Going to push as commit 95e36bc.
Since your change was applied there have been 77 commits pushed to the master branch:

  • 6443937: 8323008: filter out harmful -std* flags added by autoconf from CXX
  • c8f0418: 8310031: Parallel: Implement better work distribution for large object arrays in old gen
  • 0d30c8d: 8318590: JButton ignores margin when painting HTML text
  • 8413dc0: 8312136: Modify runtime/ErrorHandling/TestDwarf.java to split dwarf and decoder testing
  • c79c5ef: 8315241: (fs) Move toRealPath tests in java/nio/file/Path/Misc.java to separate JUnit 5 test
  • 7eea17b: 8311663: Additional refactoring of Locale tests to JUnit
  • 419e016: 8322098: os::Linux::print_system_memory_info enhance the THP output with /sys/kernel/mm/transparent_hugepage/hpage_pmd_size
  • 309a16e: 8323659: LinkedTransferQueue add and put methods call overridable offer
  • e3084fc: 8304020: Speed up test/jdk/java/util/zip/ZipFile/TestTooManyEntries.java and clarify its purpose
  • 0668efa: 8317522: Test logic for BODY_CF in AbstractThrowingSubscribers.java is wrong
  • ... and 67 more: https://git.openjdk.org/jdk21u-dev/compare/cd166703a20c4ac51bc6478e8a0bb1275d9cb913...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Jan 19, 2024
@openjdk openjdk bot closed this Jan 19, 2024
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Jan 19, 2024
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openjdk bot commented Jan 19, 2024

@fisk @mmyxym Pushed as commit 95e36bc.

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

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