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8348402: PerfDataManager stalls shutdown for 1ms #2058

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@GoeLin GoeLin commented Aug 6, 2025 •
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I backport this for parity with 21.0.9-oracle.

src/hotspot/share/runtime/objectMonitor.cpp
Resolved as comments in context are different.

src/hotspot/share/runtime/perfData.hpp
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src/hotspot/share/runtime/synchronizer.cpp
Resolved #include.

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  • JDK-8348402: PerfDataManager stalls shutdown for 1ms (Enhancement - P4)

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bridgekeeper bot commented Aug 6, 2025

👋 Welcome back goetz! 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.

@GoeLin GoeLin changed the title Goetz backport 8348402 backport 305bbdae7fe40e33cf2baa100c134bd85ecaa553 Aug 6, 2025
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❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

@openjdk openjdk bot changed the title backport 305bbdae7fe40e33cf2baa100c134bd85ecaa553 8348402: PerfDataManager stalls shutdown for 1ms Aug 6, 2025
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openjdk bot commented Aug 6, 2025

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

@openjdk openjdk bot added backport Port of a pull request already in a different code base clean Identical backport; no merge resolution required labels Aug 6, 2025
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⚠️ @GoeLin 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.

@openjdk openjdk bot added the rfr Pull request is ready for review label Aug 6, 2025
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shipilev
shipilev approved these changes Aug 6, 2025
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The backport itself looks good.

But I have a small doubt we should do it for JDK 21. Catching the critical section for FutileWakeups increment might be not worth it. In mainline, we have deleted these after replacing these PerfData events with related JFR events (https://bugs.openjdk.org/browse/JDK-8348829).

But it is a minor risk, so I would not be against it as well.

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GoeLin commented Aug 7, 2025

OK, I can set it aside for now and pick it up again if there is an additional trigger to backport it.

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shipilev commented Aug 7, 2025

OK, I can set it aside for now and pick it up again if there is an additional trigger to backport it.

I am not blocking this, just giving a perspective :)

(+): The positive impact on small applications is noticeable. We have argued about the negative impact back when it was done in mainline, and reasoned it is minor at worst. The synchronization is on FutuleWakeups path, where we already are in the world of pain.
(+): Doing the proper CS synchronization between perf data counters and their manager allows more reliable shutdown. I can see how this might mitigate some JVM shutdown crashes in the wild.
(-): We see lots of performance-sensitive applications run with -XX:-UsePerfData, where neither of these issues manifest. So the positive impact is smaller.
(-): Since this CS-taking code path is summarily removed in JDK 25. So if we backport, only JDK 21 would be taking it. This also tells us waiting for real-world JDK 25 testing is futile, since there is nothing to test.

So on balance, we can take it into JDK 21. Let's not do any prior releases, though.

@GoeLin GoeLin closed this Aug 11, 2025
@GoeLin GoeLin reopened this Aug 11, 2025
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