8310015: ZGC: Unbounded asynchronous unmapping can lead to running out of address space

[fisk]

ZGC (both generational and non-generational) use asynchronous unmapping. Today the amount of unmapping requests we can queue up is unbounded. This can lead to a classic consumer producer problem, where the consumer is slower than the producer, and we eventually run out of address space and have to shut down.
This PR introduces an upper bound for the asynchronous unmapping, to prevent the VM from shutting down. Going forwards, there are some ideas to both increase the speed of unmapping and reduce the need for unmapping, but this PR is focused only on introducing a configurable bound for async unmapping.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue

Issue

• JDK-8310015: ZGC: Unbounded asynchronous unmapping can lead to running out of address space (Bug - P2)

Reviewers

• Stefan Karlsson (@stefank - Reviewer)
• Axel Boldt-Christmas (@xmas92 - Committer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/14513/head:pull/14513
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Update a local copy of the PR:
$ git checkout pull/14513
$ git pull https://git.openjdk.org/jdk.git pull/14513/head

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$ git pr checkout 14513

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[openjdk]

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[mlbridge]

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• 00: Full (28207094)

[stefank]

Looks good.

[openjdk]

@fisk 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:

8310015: ZGC: Unbounded asynchronous unmapping can lead to running out of address space

Reviewed-by: stefank, aboldtch

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 389 new commits pushed to the master branch:

• b412fc7: 8309937: Add @sealedGraph for some Panama FFM interfaces
• fb024fd: 8248149: G1: change _cleaning_claimed from int to bool
• c2b043e: 8310183: Update GitHub Actions to use boot JDK for building jtreg
• 238c51e: 8293069: Make -XX:+Verbose less verbose
• 8c9b85a: 8303916: ThreadLists.java inconsistent results
• 227656f: 8309408: Thread.sleep cleanup
• 32243ef: 8310128: Switch with unnamed patterns erroneously non-exhaustive
• cfae6ef: 8309778: java/nio/file/Files/CopyAndMove.java fails when using second test directory
• db133db: 8310106: sun.security.ssl.SSLHandshake.getHandshakeProducer() incorrectly checks handshakeConsumers
• 353e581: 8309747: Update --release 21 symbol information for JDK 21 build 27
• ... and 379 more: https://git.openjdk.org/jdk/compare/c4408278d1012746c91ba4c31068538850c68d30...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.

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

[xmas92]

Looks good.

[fisk]

Thanks for the reviews @xmas92 and @stefank!
/integrate

[openjdk]

Going to push as commit 4229baf.
Since your change was applied there have been 405 commits pushed to the master branch:

• 266f983: 8308855: ARM32: TestBooleanVector crashes after 8300257
• 6a63bad: 8310191: com/sun/tools/attach/warnings/DynamicLoadWarningTest.java second failure on AIX
• 6473a7d: 8310107: os::trace_page_sizes_for_requested_size should name alignment as requested page size
• 02aaab1: 8310126: C1: Missing receiver null check in Reference::get intrinsic
• 492d25c: 8309601: [JVMCI] AMD64#getLargestStorableKind returns incorrect mask kind
• 959a61f: 8310259: Pin msys2/setup-msys2 github action to a specific commit
• bcc4d36: 8309511: Regression test ExtraImportSemicolon.java refers to the wrong bug
• 71baf00: 8309605: StubRoutines are not used by SA
• 16134f4: 8310211: serviceability/jvmti/thread/GetStackTrace/getstacktr03/getstacktr03.java failing
• d6c2ee3: 8310054: ScrollPane insets are incorrect
• ... and 395 more: https://git.openjdk.org/jdk/compare/c4408278d1012746c91ba4c31068538850c68d30...master

Your commit was automatically rebased without conflicts.

[openjdk]

@fisk Pushed as commit 4229baf.

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

[fisk]

/backport jdk21

[openjdk]

@fisk the backport was successfully created on the branch fisk-backport-4229baf9 in my personal fork of openjdk/jdk21. To create a pull request with this backport targeting openjdk/jdk21:master, just click the following link:

➡️ Create pull request

The title of the pull request is automatically filled in correctly and below you find a suggestion for the pull request body:

Hi all,

This pull request contains a backport of commit 4229baf9 from the openjdk/jdk repository.

The commit being backported was authored by Erik Österlund on 19 Jun 2023 and was reviewed by Stefan Karlsson and Axel Boldt-Christmas.

Thanks!

If you need to update the source branch of the pull then run the following commands in a local clone of your personal fork of openjdk/jdk21:

$ git fetch https://github.com/openjdk-bots/jdk21.git fisk-backport-4229baf9:fisk-backport-4229baf9
$ git checkout fisk-backport-4229baf9
# make changes
$ git add paths/to/changed/files
$ git commit --message 'Describe additional changes made'
$ git push https://github.com/openjdk-bots/jdk21.git fisk-backport-4229baf9