8297979: ZGC: Ensure consistent MemoryUsage from MemoryMXBean.getHeapMemoryUsage()

[kstefanj]

Please review this bugfix to ensure a consistent MemoryUsageobject is returned when using MemoryMXBean.getHeapMemoryUsage()

Summary
In ZGC the MemoryUsage returned was created using the base implementation in CollectedHead. This implementation just queries the underlying heap for used, capacityand max_capacity, and since these values can be updated concurrently with ZGC we need to have a specialized implementation that handles this to ensure consistent values are returned. Such implementation is already present and used when the usage is quired through a MemoryPool, so this change just re-uses that.

Testing
Verified locally that this fixes the test that previously failed.

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Progress

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• Commit message must refer to an issue

Issue

• JDK-8297979: ZGC: Ensure consistent MemoryUsage from MemoryMXBean.getHeapMemoryUsage()

Reviewers

• Stefan Karlsson (@stefank - Reviewer)
• Albert Mingkun Yang (@albertnetymk - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk20 pull/39/head:pull/39
$ git checkout pull/39

Update a local copy of the PR:
$ git checkout pull/39
$ git pull https://git.openjdk.org/jdk20 pull/39/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 39

View PR using the GUI difftool:
$ git pr show -t 39

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk20/pull/39.diff

[bridgekeeper]

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[openjdk]

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

• hotspot-gc

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[mlbridge]

Webrevs

• 01: Full - Incremental (c0edb882)
• 00: Full (16e16b7c)

[stefank]

Looks good. Thanks for fixing!

[openjdk]

@kstefanj 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:

8297979: ZGC: Ensure consistent MemoryUsage from MemoryMXBean.getHeapMemoryUsage()

Reviewed-by: stefank, ayang

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 3 new commits pushed to the master branch:

• 48f6127: 8298376: ZGC: thaws stackChunk with stale oops
• 22a6b59: 8298727: Trees.getPath may crash for unnamed package
• 323e574: 8298371: monitors_on_stack extracts unprocessed oops

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.

[kstefanj]

Thanks for the reviews @stefank and @albertnetymk
/integrate

[openjdk]

Going to push as commit c47e64e.
Since your change was applied there have been 7 commits pushed to the master branch:

• 03a694a: 8298083: The "CheckBox/RadioButton[Enabled/Disabled].textForeground" stoped working
• c7d7e7e: 8298888: ProblemList gc/g1/TestVerifyGCType.java on linux and macosx
• ca39eb9: 7093322: (fs spec) Files.newBufferedWriter should be clear when coding errors are detected
• 2c42499: 8298050: Add links to graph output for javadoc
• 48f6127: 8298376: ZGC: thaws stackChunk with stale oops
• 22a6b59: 8298727: Trees.getPath may crash for unnamed package
• 323e574: 8298371: monitors_on_stack extracts unprocessed oops

Your commit was automatically rebased without conflicts.

[openjdk]

@kstefanj Pushed as commit c47e64e.

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