8387907: Shenandoah: Marking loop prefetch

[shipilev]

Dramatically improves Shenandoah performance.

Additional testing:

• Linux x86_64 server fastdebug, jcstress 8 hour run
• Linux x86_64 server fastdebug, hotspot_gc_shenandoah
• Linux AArch64 server fastdebug, hotspot_gc_shenandoah
• Linux x86_64 server fastdebug, hotspot_gc_shenandoah with -XX:TieredStopAtLevel=1
• Linux AArch64 server fastdebug, hotspot_gc_shenandoah with -XX:TieredStopAtLevel=1
• Linux x86_64 server fastdebug, all with -XX:+UseShenandoahGC
• Linux AArch64 server fastdebug, all with -XX:+UseShenandoahGC
• Linux x86_64 server fastdebug, all with -XX:+UseShenandoahGC -XX:TieredStopAtLevel=1
• Linux AArch64 server fastdebug, all with -XX:+UseShenandoahGC -XX:TieredStopAtLevel=1

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• I confirm that I make this contribution in accordance with the OpenJDK Interim AI Policy.

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Progress

• JDK-8387907 needs maintainer approval
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8387907: Shenandoah: Marking loop prefetch (Enhancement - P4 - Approved)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/746/head:pull/746
$ git checkout pull/746

Update a local copy of the PR:
$ git checkout pull/746
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/746/head

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Checkout this PR locally:
$ git pr checkout 746

View PR using the GUI difftool:
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Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/746.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back shade! 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]

@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:

8387907: Shenandoah: Marking loop prefetch

You can use pull request commands such as /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 25 new commits pushed to the master branch:

• 5bf925d: 8374516: -version asserts with "-XX:+UseAESCTRIntrinsics -XX:-UseAES": "need AES instructions and misaligned SSE support" in generate_counterMode_AESCrypt_Parallel()
• 8d67111: 8375443: AVX-512: Disabling through UseSHA doesn't affect UseSHA3Intrinsics
• b221198: 8370481: C2 SuperWord: Long/Integer.compareUnsigned return wrong value in SLP
• ... and 22 more: https://git.openjdk.org/jdk25u-dev/compare/c6899d38e9459563c1f048f985eb8d0e45545881...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.

[openjdk]

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

[openjdk]

⚠️ @shipilev 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.

[mlbridge]

Webrevs

• 00: Full (565ef173)

[shipilev]

/approval request Dramatically improves Shenandoah marking performance. Applies cleanly. Tests pass, performance improves at the same level as in mainline. Risk is medium-low: simple change in production paths, isolated to Shenandoah, no bugtail since 6 weeks in mainline.

[openjdk]

@shipilev
8387907: The approval request has been created successfully.

[shipilev]

Push approval granted.

/integrate

[openjdk]

Going to push as commit b4b9425.
Since your change was applied there have been 29 commits pushed to the master branch:

• 108e57a: 8387721: C2: Print Node barrier data
• 79319cb: 8383635: Improve performance of ML-KEM's implKyberNttMultJava() method
• 2112b86: 8389509: SetPrinterDevice check GlobalAlloc return value
• ... and 26 more: https://git.openjdk.org/jdk25u-dev/compare/c6899d38e9459563c1f048f985eb8d0e45545881...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit b4b9425.

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