8324933: ConcurrentHashTable::statistics_calculate synchronization is expensive

[fisk]

In the ConcurrentHashTable::statistics_calculate function, we enter and exit a ScopedCS with the global counter for every single bucket. This has showed up to be pretty intense on some machines. We should make the synchronization a bit less intense here. This patch adds simple batching so we synchronize once per 128 buckets instead of every single one.

---

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-8324933: ConcurrentHashTable::statistics_calculate synchronization is expensive (Enhancement - P4)

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to 3b26cf9c
• Coleen Phillimore (@coleenp - Reviewer) ⚠️ Review applies to 3b26cf9c

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/17629/head:pull/17629
$ git checkout pull/17629

Update a local copy of the PR:
$ git checkout pull/17629
$ git pull https://git.openjdk.org/jdk.git pull/17629/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 17629

View PR using the GUI difftool:
$ git pr show -t 17629

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/17629.diff

Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back eosterlund! 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]

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

• hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 03: Full - Incremental (cb71f9c8)
• 02: Full - Incremental (3b26cf9c)
• 01: Full - Incremental (a6a7e3c8)
• 00: Full (f0b8f46a)

[fisk]

Thanks for the review @tschatzl! I liked your suggested change. It looks simpler now.

[coleenp]

This seems reasonable, as long as the critical section is held throughout a bucket iteration.

[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:

8324933: ConcurrentHashTable::statistics_calculate synchronization is expensive

Reviewed-by: tschatzl, coleenp

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 255 new commits pushed to the master branch:

• 130f429: 8325403: Add SystemGC JMH benchmarks
• 9c852df: 8318966: Some methods make promises about Java array element alignment that are too strong
• 737b4c5: 8323883: JFR AssertionError: Missing object ID 15101
• 61f2493: 8325767: Serial: Move transform_stack_chunk out of TenuredGeneration::promote
• 8dc5976: 8325809: JFR: Remove unnecessary annotation
• 84965ea: 8322630: Remove ICStubs and related safepoints
• 0c2def0: 8325653: Erroneous exhaustivity analysis for primitive patterns
• d003996: 8325743: test/jdk/java/nio/channels/unixdomain/SocketOptions.java enhance user name output in error case
• ea98de6: 8325449: [BACKOUT] use "dmb.ishst+dmb.ishld" for release barrier
• 7f6bb71: 8319799: Recursive lightweight locking: x86 implementation
• ... and 245 more: https://git.openjdk.org/jdk/compare/bccd823c8e40863bed70ff5b24772843203871a5...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.

[tschatzl]

lgtm. A comment why we need to do the batched iteration (without looking at versioning system logs) would be nice.

[fisk]

Thanks for the reviews, @coleenp and @tschatzl! I will add a comment before integrating.

[fisk]

/integrate

[openjdk]

Going to push as commit 0e2fdc9.
Since your change was applied there have been 263 commits pushed to the master branch:

• 8cb9b47: 8321282: RISC-V: SpinPause() not implemented
• 1aae980: 8323994: gtest runner repeats test name for every single gtest assertion
• 810daf8: 8325910: Rename jnihelper.h
• 22e8181: 8325682: Rename nsk_strace.h
• b823fa4: 8325574: Shenandoah: Simplify and enhance reporting of requested GCs
• 09d4936: 8252136: Several methods in hotspot are missing "static"
• f6e2851: 8316340: (bf) Missing {@inheritdoc} for exception in MappedByteBuffer::compact
• 53878ee: 8325643: G1: Refactor G1FlushHumongousCandidateRemSets
• 130f429: 8325403: Add SystemGC JMH benchmarks
• 9c852df: 8318966: Some methods make promises about Java array element alignment that are too strong
• ... and 253 more: https://git.openjdk.org/jdk/compare/bccd823c8e40863bed70ff5b24772843203871a5...master

Your commit was automatically rebased without conflicts.

[openjdk]

@fisk Pushed as commit 0e2fdc9.

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