8320370: NMT: Change MallocMemorySnapshot to simplify code.

[shipilev]

Clean backport to improve NMT initialization and provide cleanliness for other backports.

Additional testing:

• MacOS AArch64 server fastdebug, runtime/NMT

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8320370 needs maintainer approval

Issue

• JDK-8320370: NMT: Change MallocMemorySnapshot to simplify code. (Enhancement - P4 - Approved)

Reviewers

• Thomas Stuefe (@tstuefe - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/552/head:pull/552
$ git checkout pull/552

Update a local copy of the PR:
$ git checkout pull/552
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/552/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 552

View PR using the GUI difftool:
$ git pr show -t 552

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/552.diff

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[bridgekeeper]

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[openjdk]

@shipilev 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:

8320370: NMT: Change MallocMemorySnapshot to simplify code.

Reviewed-by: stuefe

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 8 new commits pushed to the master branch:

• c12dfc3: 8330523: Reduce runtime and improve efficiency of KeepAliveTest
• ddecbe5: 8330815: Use pattern matching for instanceof in KeepAliveCache
• 93d091a: 8314573: G1: Heap resizing at Remark does not take existing eden regions into account
• 41fda4a: 8319376: ParallelGC: Forwarded objects found during heap inspection
• ec6b326: 8310913: Move ReferencedKeyMap to jdk.internal so it may be shared
• 92b43c5: 8317007: Add bulk removal of dead nmethods during class unloading
• ed2f5a8: 8310228: Improve error reporting for uncaught native exceptions on Windows
• 7a400f2: 8309890: TestStringDeduplicationInterned.java waits for the wrong condition

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.

[mlbridge]

Webrevs

• 00: Full (df396f40)

[shipilev]

/approval request Clean backport to improve NMT initialization and provide cleanliness for other backports. NMT tests pass. Risk is low-medium, affects NMT, but problems should be easily detectable.

[openjdk]

@shipilev
8320370: The approval request has been created successfully.

[shipilev]

I think bots do not treat this backport as clean, because the afftected files were moved from services to nmt. So I need a formal review for this. @tstuefe, maybe?

[tstuefe]

Looks fine.

[shipilev]

Thank you!

/integrate

[openjdk]

Going to push as commit 153de5a.
Since your change was applied there have been 10 commits pushed to the master branch:

• fa874b3: 8325621: Improve jspawnhelper version checks
• e3a9226: 8330524: Linux ppc64le compile warning with clang in os_linux_ppc.cpp
• c12dfc3: 8330523: Reduce runtime and improve efficiency of KeepAliveTest
• ddecbe5: 8330815: Use pattern matching for instanceof in KeepAliveCache
• 93d091a: 8314573: G1: Heap resizing at Remark does not take existing eden regions into account
• 41fda4a: 8319376: ParallelGC: Forwarded objects found during heap inspection
• ec6b326: 8310913: Move ReferencedKeyMap to jdk.internal so it may be shared
• 92b43c5: 8317007: Add bulk removal of dead nmethods during class unloading
• ed2f5a8: 8310228: Improve error reporting for uncaught native exceptions on Windows
• 7a400f2: 8309890: TestStringDeduplicationInterned.java waits for the wrong condition

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 153de5a.

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