8306738: Select num workers for safepoint ParallelCleanupTask

[shipilev]

Unclean backport to considerably improve the safepoint cleanup times. The backport is not clean, because the WorkGang -> WorkerThreads rename is missing. The is also the addition of Dictionary::does_any_dictionary_needs_resizing check, because JDK 17 is still have that resize code in JDK 17.

Additional testing:

• Ad-hoc benchmarks
• Linux x86_64 fastdebug tier1 tier2 tier3

The experiments (see original PR) show we win big on this:

---

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

Issue

• JDK-8306738: Select num workers for safepoint ParallelCleanupTask (Enhancement - P4)

Reviewers

• Paul Hohensee (@phohensee - Reviewer) ⚠️ Review applies to beb12598

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk17u-dev.git pull/1379/head:pull/1379
$ git checkout pull/1379

Update a local copy of the PR:
$ git checkout pull/1379
$ git pull https://git.openjdk.org/jdk17u-dev.git pull/1379/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1379

View PR using the GUI difftool:
$ git pr show -t 1379

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk17u-dev/pull/1379.diff

Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back shade! A progress list of the required criteria for merging this PR into pr/1377 will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

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

[mlbridge]

Webrevs

• 03: Full - Incremental (ceaf49d0)
• 02: Full (e22e9e37)
• 01: Full - Incremental (beb12598)
• 00: Full (beb12598)

[phohensee]

Lgtm.

[shipilev]

Lgtm.

Thank you! I marked this for maintainer approval.

I'll probably wait a bit anyhow, to collect more reviews and/or mainline bugs, if any.

[openjdk-notifier]

The parent pull request that this pull request depends on has now been integrated and the target branch of this pull request has been updated. This means that changes from the dependent pull request can start to show up as belonging to this pull request, which may be confusing for reviewers. To remedy this situation, simply merge the latest changes from the new target branch into this pull request by running commands similar to these in the local repository for your personal fork:

git checkout JDK-8306738-safepoint-cleanup-num-workers
git fetch https://git.openjdk.org/jdk17u-dev.git master
git merge FETCH_HEAD
# if there are conflicts, follow the instructions given by git merge
git commit -m "Merge master"
git push

[openjdk]

@shipilev this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout JDK-8306738-safepoint-cleanup-num-workers
git fetch https://git.openjdk.org/jdk17u-dev.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

[openjdk]

@shipilev Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

[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:

8306738: Select num workers for safepoint ParallelCleanupTask

Reviewed-by: phh

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 no new commits pushed to the master branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential 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.

[shipilev]

The change was in mainline for over a month, with no ill effects reported.
This is an easy win for tail latencies caused by safepoint cleanups.
I would continue monitoring mainline for any related issues to this.

/integrate

[openjdk]

Going to push as commit 0368ae9.
Since your change was applied there have been 7 commits pushed to the master branch:

• 249ddf4: 8293252: Shenandoah: ThreadMXBean synchronizer tests crash with aggressive heuristics
• 5a4e374: 8309959: JFR: Display N/A for missing data amount
• 6c81bf5: 8295811: serviceability/sa/TestObjectAlignment.java fails on x86_32
• c6f6db2: 8295657: SA: Allow larger object alignments
• 55c0eaa: 8272654: Mark word accesses should not use Access API
• 7697ab4: 8309550: jdk.jfr.internal.Utils::formatDataAmount method should gracefully handle amounts equal to Long.MIN_VALUE
• 852c26c: 8279545: Buffer overrun in reverse_words of sharedRuntime_x86_64.cpp:3517

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 0368ae9.

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