July 2025 - hotspot-jfr-dev

RFR: 8362556: New test jdk/jfr/event/io/TestIOTopFrame.java is failing on all platforms
by Erik Gahlin 19 Jul '25

19 Jul '25

Could I have a review of a PR that adjusts the number of frames to skip for the FileRead event? The problem was that an intermediary frame was removed during review in a dependent PR, but the offset was not updated. Testing: jdk/jdk/jfr Thanks Erik ------------- Commit messages: - Initial Changes: https://git.openjdk.org/jdk/pull/26378/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26378&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8362556 Stats: 3 lines in 1 file changed: 1 ins; 1 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/26378.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26378/head:pull/26378 PR: https://git.openjdk.org/jdk/pull/26378

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[jdk25] RFR: 8361639: JFR: Incorrect top frame for I/O events
by Erik Gahlin 17 Jul '25

17 Jul '25

8361639: JFR: Incorrect top frame for I/O events ------------- Commit messages: - Backport 1a6cbe421facab0de1c7162f2762258664338814 Changes: https://git.openjdk.org/jdk/pull/26367/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26367&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8361639 Stats: 414 lines in 6 files changed: 397 ins; 12 del; 5 mod Patch: https://git.openjdk.org/jdk/pull/26367.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26367/head:pull/26367 PR: https://git.openjdk.org/jdk/pull/26367

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RFR: 8361639: JFR: Incorrect top frame for I/O events
by Erik Gahlin 17 Jul '25

17 Jul '25

Could I have a review of the change that ensures that the top frame for I/O events is not an internal JDK method, such as FileReadEvent::offer? This change is dependent on [JDK-8361640](https://bugs.openjdk.org/browse/JDK-8361640). Testing: tier1, tier2 + jdk/jdk/jfr Thanks Erik ------------- Commit messages: - Cleanup and socket adapters - Use switch expression - Revert accidental move - Fix whitespace - Initial Changes: https://git.openjdk.org/jdk/pull/26211/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26211&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8361639 Stats: 375 lines in 6 files changed: 358 ins; 12 del; 5 mod Patch: https://git.openjdk.org/jdk/pull/26211.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26211/head:pull/26211 PR: https://git.openjdk.org/jdk/pull/26211

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[jdk25] RFR: 8358619: Fix interval recomputation in CPU Time Profiler
by Johannes Bechberger 16 Jul '25

16 Jul '25

Fixes the interval recomputation in JEP 509, tested in the SAP CI. ------------- Commit messages: - Backport c70258ca1cd074392b5bf844bf6f7b80601f45cc Changes: https://git.openjdk.org/jdk/pull/26313/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26313&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8358619 Stats: 208 lines in 10 files changed: 122 ins; 11 del; 75 mod Patch: https://git.openjdk.org/jdk/pull/26313.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26313/head:pull/26313 PR: https://git.openjdk.org/jdk/pull/26313

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[jdk25] RFR: 8358621: Reduce busy waiting in worse case at the synchronization point returning from native in CPU Time Profiler
by Johannes Bechberger 16 Jul '25

16 Jul '25

Hi all, This pull request contains a backport of commit [d2082c58](https://github.com/openjdk/jdk/commit/d2082c58ff086eb37c6211a8d1b… from the [openjdk/jdk](https://git.openjdk.org/jdk) repository. The commit being backported was authored by Johannes Bechberger on 15 Jul 2025 and was reviewed by Aleksey Shipilev, Jaroslav Bachorik and Erik Gahlin. Thanks! ------------- Commit messages: - Backport d2082c58ff086eb37c6211a8d1b813cdfedc2259 Changes: https://git.openjdk.org/jdk/pull/26320/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26320&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8358621 Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/26320.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26320/head:pull/26320 PR: https://git.openjdk.org/jdk/pull/26320

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[jdk25] RFR: 8362097: JFR: Active Settings view broken
by Erik Gahlin 16 Jul '25

16 Jul '25

8362097: JFR: Active Settings view broken ------------- Commit messages: - Backport 25e509b0db4f35b3b8fbfeb7ec84cc0e0fed89d1 Changes: https://git.openjdk.org/jdk/pull/26329/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26329&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8362097 Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/26329.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26329/head:pull/26329 PR: https://git.openjdk.org/jdk/pull/26329

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RFR: 8361640: JFR: RandomAccessFile::readLine emits events for each character
by Erik Gahlin 15 Jul '25

15 Jul '25

Could I have a review of the change that prevents RandomAccessFile::readLine from emitting an event per character? This leads to unnecessary overhead, both with or without JFR enabled. Testing: tier1 + jdk/jdk/jfr Thanks Erik ------------- Commit messages: - Remove mistakenly added file - Initial Changes: https://git.openjdk.org/jdk/pull/26210/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26210&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8361640 Stats: 21 lines in 1 file changed: 19 ins; 0 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/26210.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26210/head:pull/26210 PR: https://git.openjdk.org/jdk/pull/26210

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RFR: 8358621: Avoid using a spinlock as the synchronization point returning from native in CPU Time Profiler
by Johannes Bechberger 15 Jul '25

15 Jul '25

Simple optimization to avoid busy waiting in safepoint handlers. ------------- Commit messages: - Improve busy waiting Changes: https://git.openjdk.org/jdk/pull/26314/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26314&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8358621 Stats: 8 lines in 1 file changed: 7 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/26314.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26314/head:pull/26314 PR: https://git.openjdk.org/jdk/pull/26314

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RFR: 8358619: Fix interval recomputation in CPU Time Profiler
by Johannes Bechberger 15 Jul '25

15 Jul '25

Fixes the recomputation issue by passing either the rate or the period directly to the sampler (instead of just the rate value with the period value converted into a rate). This prevents issues when the number of cores changes during the JFR recording. ------------- Commit messages: - 8358619: Fix interval recomputation in CPU Time Profiler Changes: https://git.openjdk.org/jdk/pull/25775/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25775&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8358619 Stats: 327 lines in 11 files changed: 180 ins; 78 del; 69 mod Patch: https://git.openjdk.org/jdk/pull/25775.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/25775/head:pull/25775 PR: https://git.openjdk.org/jdk/pull/25775

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Question about the priority in Old Object Sample event
by Takuya Kiriyama (Fujitsu) 15 Jul '25

15 Jul '25

Hi, I'm investigating Old Object Sample event in JFR that is useful for memory leak analysis, but I'm finding some implementation puzzling. I'd be grateful for any insights from those with more experience. Old Object Sample tracks a fixed number of objects on the heap for as long as they are live. Marcus' article [1] was very useful for understanding this event. However, I have doubts about the priority of the samples stored in the priority queue. As mentioned in the article, the priority called "span" is determined by the memory size, giving more weight to samples that are causing more serious leaks. The code that implements span [2]: ``` _total_allocated += allocated; const size_t span = _total_allocated - _priority_queue->total(); ``` Here, "_total_allocated" is the total memory size allocated so far, and "_priority_queue->total()" is the total size of the priority queue. Since "_total_allocated" increases monotonically, the span of samples allocated later tends to increase as time passes For memory leak analysis, it is very important to pick which objects out of a large number of objects. I didn't understand why objects generated later tend to take precedence. Any advice would be greatly appreciated. Regards, Takuya

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