8367949: JFR: MethodTrace double-counts methods that catch their own exceptions by rm-gh-8 · Pull Request #182 · openjdk/jdk25u-dev

rm-gh-8 · 2026-01-26T18:52:50Z

Backporting JDK-8367949: JFR: MethodTrace double-counts methods that catch their own exceptions.

This PR fixes a bug in JEP 520's method tracing instrumentation. The current implementation incorrectly instruments throw bytecodes as method exits, causing:

Overcounting: Exceptions caught within the same method are wrongly counted as extra calls
Undercounting: Method calls aren't counted when exceptions are thrown by callees or when JVM implicit exceptions (like NPE) occur

Ran related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:

make test TEST=jdk_jfr

Results attached:

linux-aarch64-specific-test.log
linux-x64-specific-test.log
macos-aarch64-specific-test.log
windows-x64-specific-test.log

Progress

JDK-8367949 needs maintainer approval
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8367949: JFR: MethodTrace double-counts methods that catch their own exceptions (Bug - P3 - Approved)

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$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/182/head:pull/182
$ git checkout pull/182

Update a local copy of the PR:
$ git checkout pull/182
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/182/head

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$ git pr checkout 182

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https://git.openjdk.org/jdk25u-dev/pull/182.diff

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bridgekeeper · 2026-01-26T18:53:37Z

👋 Welcome back rm-gh-8! 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 · 2026-01-26T18:55:53Z

@rm-gh-8 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:

8367949: JFR: MethodTrace double-counts methods that catch their own exceptions

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 5 new commits pushed to the master branch:

fe129fc: 8357086: os::xxx functions returning memory size should return size_t
2fb3e9c: 8377932: AOT cache is not rejected when JAR file has changed
5b75179: 8374769: PPC: MASM::pop_cont_fastpath() should reset _cont_fastpath if SP == _cont_fastpath
... and 2 more: https://git.openjdk.org/jdk25u-dev/compare/79f0f9ded514c763ad085abb5b156a81bf633c16...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.

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➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

openjdk · 2026-01-26T18:56:19Z

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

openjdk · 2026-01-26T20:40:46Z

⚠️ @rm-gh-8 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 · 2026-01-26T20:45:44Z

Webrevs

01: Full - Incremental (514ffc94)
00: Full (ac2a91de)

rm-gh-8 · 2026-01-26T20:46:19Z

/approval request for backport of JDK-8367949: JFR: MethodTrace double-counts methods that catch their own exceptions.

This PR fixes a bug in JFR's method tracing instrumentation.

This backport has customer demand.

Low-medium risk - Fixes the incorrect call counting behavior, but the constructor edge cases suggests an incomplete solution.

openjdk · 2026-01-26T20:47:31Z

@rm-gh-8
8367949: The approval request has been created successfully.

bridgekeeper · 2026-02-24T01:34:28Z

@rm-gh-8 This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

rm-gh-8 · 2026-02-24T15:09:08Z

/keepalive

openjdk · 2026-02-24T15:09:54Z

@rm-gh-8 The pull request is being re-evaluated and the inactivity timeout has been reset.

GoeLin · 2026-03-08T10:01:16Z

HI @rm-gh-8
I will have a second look at this. Please give an eligible reason for the backport. Similar for others.

GoeLin · 2026-03-12T10:33:48Z

HI @rm-gh-8
could you please merge head and rerun GHA tests?
Thanks.

…8367949-V25

rm-gh-8 · 2026-03-12T16:54:17Z

@GoeLin Done.

rm-gh-8 · 2026-03-12T17:15:02Z

/approval request for backport of JDK-8367949: JFR: MethodTrace double-counts methods that catch their own exceptions.

Why It's Important:

JFR method tracing produced incorrect invocation counts. Methods that caught their own exceptions were double-counted, while methods where exceptions propagated from callees or were implicit JVM exceptions (NPE, OOME) were never counted at all. This undermines the reliability of jdk.MethodTrace and jdk.MethodTiming events for performance analysis and debugging.

openjdk · 2026-03-12T17:17:27Z

@rm-gh-8
8367949: The approval request has been updated successfully.

rm-gh-8 · 2026-03-16T14:17:06Z

/integrate

openjdk · 2026-03-16T14:21:47Z

@rm-gh-8
Your change (at version 514ffc9) is now ready to be sponsored by a Committer.

shipilev · 2026-03-16T15:16:11Z

Maybe we should wait a bit, until @egahlin gives us the all-clear about this? See Erik's comment in the issue.

egahlin · 2026-03-16T19:01:50Z

Maybe we should wait a bit, until @egahlin gives us the all-clear about this? See Erik's comment in the issue.

Mikael found an issue in the method timing event last week (now fixed in JDK 27) while doing some manual experiments. Given that JDK 25 was released less than six months ago and that what we had before this patch works in most cases, I don’t think we need to hurry it into a backport.

My plan is to update the Swing GUI I wrote for JDK 25 and see that everything looks good after the patch.
https://egahlin.github.io/2025/05/31/whats-new-in-jdk-25.html

I will have more time in the next couple weeks.

egahlin · 2026-03-27T14:57:46Z

I’ve now had some time to try the new implementation manually, using tracing and timing on java.lang.Object and a few other tricky classes that are hard to have in unit tests. I found a bug, but it also exists in JDK 25.

I also tried the new implementation in the updated GUI, and it works fine.

shipilev · 2026-03-30T08:21:18Z

Awesome, thanks!

So to recap, there is nothing blocking from this going into 25u, right, @egahlin?

I found a bug, but it also exists in JDK 25.

Cool. Do you have the bug ID for it?

egahlin · 2026-03-30T21:51:59Z

Awesome, thanks!

So to recap, there is nothing blocking from this going into 25u, right, @egahlin?

Correct.

I found a bug, but it also exists in JDK 25.

Cool. Do you have the bug ID for it?

https://bugs.openjdk.org/browse/JDK-8381170

Backport fa2eb626478806dc64fe03d8729f53f7ed26a172

ac2a91d

openjdk bot changed the title ~~Backport fa2eb626478806dc64fe03d8729f53f7ed26a172~~ 8367949: JFR: MethodTrace double-counts methods that catch their own exceptions Jan 26, 2026

openjdk bot added backport Port of a pull request already in a different code base clean Identical backport; no merge resolution required labels Jan 26, 2026

rm-gh-8 marked this pull request as ready for review January 26, 2026 20:38

openjdk bot added the rfr Pull request is ready for review label Jan 26, 2026

openjdk bot added the approval Requires approval; will be removed when approval is received label Jan 26, 2026

Merge branch 'master' of https://git.openjdk.org/jdk25u-dev into JDK-…

514ffc9

…8367949-V25

openjdk bot added ready Pull request is ready to be integrated and removed approval Requires approval; will be removed when approval is received labels Mar 16, 2026

openjdk bot added the sponsor Pull request is ready to be sponsored label Mar 16, 2026

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