November 2025 - hotspot-jfr-dev

RFR: 8370715: JFR: Races are possible when dumping recordings
by Robert Toyonaga 04 Dec '25

04 Dec '25

#### Summary This PR changes the JFR snapshot dumping code so that multiple JFR recordings (potentially from different processes) racing to write the same dump destination won't mix their data. #### Problem The dump destination file is created and/or wiped when a recording is started, but not wiped again before actually copying over the chunks during a dump. So in the window of time between creating/wiping and dumping chunks, another recording could write to the same dump destination and have it's chunks added to the snapshot. This can happen with either a single JVM or multiple JVMs that are racing. #### Proposed fix This PR ensures that any data previously written to the dump destination is wiped before the new recording's data is written. File locking is also done while chunks are being written. Testing: - new test `jdk/jdk/jfr/api/recording/dump/TestDumpOverwrite.java` - Tier 1 ------------- Commit messages: - small changes to transferChunks and add test Changes: https://git.openjdk.org/jdk/pull/28460/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28460&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8370715 Stats: 87 lines in 2 files changed: 86 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/28460.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28460/head:pull/28460 PR: https://git.openjdk.org/jdk/pull/28460

4 11

RFR: 8372587: Put jdk/jfr/jvm/TestWaste.java into the ProblemList
by Kerem Kat 03 Dec '25

03 Dec '25

It still fails in oracle environment as described in [JDK-8371630](https://bugs.openjdk.org/browse/JDK-8371630). ------------- Commit messages: - 8372587: Put jdk/jfr/jvm/TestWaste.java into the ProblemList Changes: https://git.openjdk.org/jdk/pull/28539/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28539&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8372587 Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/28539.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28539/head:pull/28539 PR: https://git.openjdk.org/jdk/pull/28539

3 8

Re: RFR: 8365400: Enhance JFR to emit file and module metadata for class loading [v6]
by Markus Grönlund 27 Nov '25

27 Nov '25

> Greetings, > > this enhancement adds a "source" field, label "Location" to the jdk.ClassDefine event. > > To enable this functionality, JFR needs a concurrent symbol table. We can build a simpler version of a concurrent hash table, taking advantage of the JFR epoch system. This will be useful also for planned future enhancements. > > Extensions are made to AOT to consistently report identical canonical paths for classes as non-AOT code paths. > > Testing: jdk_jfr, manual AOT verification, stress testing > > Thanks > Markus Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision: jfr views for class source ------------- Changes: - all: https://git.openjdk.org/jdk/pull/28505/files - new: https://git.openjdk.org/jdk/pull/28505/files/2e8809b0..c0e1124e Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=05 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=04-05 Stats: 26 lines in 3 files changed: 21 ins; 0 del; 5 mod Patch: https://git.openjdk.org/jdk/pull/28505.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28505/head:pull/28505 PR: https://git.openjdk.org/jdk/pull/28505

1 0

Re: RFR: 8365400: Enhance JFR to emit file and module metadata for class loading [v5]
by Markus Grönlund 27 Nov '25

27 Nov '25

> Greetings, > > this enhancement adds a "source" field, label "Location" to the jdk.ClassDefine event. > > To enable this functionality, JFR needs a concurrent symbol table. We can build a simpler version of a concurrent hash table, taking advantage of the JFR epoch system. This will be useful also for planned future enhancements. > > Extensions are made to AOT to consistently report identical canonical paths for classes as non-AOT code paths. > > Testing: jdk_jfr, manual AOT verification, stress testing > > Thanks > Markus Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision: remove ------------- Changes: - all: https://git.openjdk.org/jdk/pull/28505/files - new: https://git.openjdk.org/jdk/pull/28505/files/d312adba..2e8809b0 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=04 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=03-04 Stats: 2 lines in 2 files changed: 1 ins; 1 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/28505.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28505/head:pull/28505 PR: https://git.openjdk.org/jdk/pull/28505

1 0

RFR: 8372586: Crashes on ppc64(le) after JDK-8371368
by Markus Grönlund 27 Nov '25

27 Nov '25

Greetings, Follow-up adjustment to JDK-8371368. Testing: aarch64 with -XX:+PreserveFramePointer Thanks Markus ------------- Commit messages: - 8372586 Changes: https://git.openjdk.org/jdk/pull/28509/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28509&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8372586 Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/28509.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28509/head:pull/28509 PR: https://git.openjdk.org/jdk/pull/28509

2 4

Re: RFR: 8365400: Enhance JFR to emit file and module metadata for class loading [v4]
by Markus Grönlund 26 Nov '25

26 Nov '25

> Greetings, > > this enhancement adds a "source" field, label "Location" to the jdk.ClassDefine event. > > To enable this functionality, JFR needs a concurrent symbol table. We can build a simpler version of a concurrent hash table, taking advantage of the JFR epoch system. This will be useful also for planned future enhancements. > > Extensions are made to AOT to consistently report identical canonical paths for classes as non-AOT code paths. > > Testing: jdk_jfr, manual AOT verification, stress testing > > Thanks > Markus Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision: adjustments ------------- Changes: - all: https://git.openjdk.org/jdk/pull/28505/files - new: https://git.openjdk.org/jdk/pull/28505/files/af55c2a7..d312adba Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=03 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=02-03 Stats: 50 lines in 4 files changed: 22 ins; 3 del; 25 mod Patch: https://git.openjdk.org/jdk/pull/28505.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28505/head:pull/28505 PR: https://git.openjdk.org/jdk/pull/28505

1 0

Re: RFR: 8365400: Enhance JFR to emit file and module metadata for class loading [v3]
by Markus Grönlund 26 Nov '25

26 Nov '25

> Greetings, > > this enhancement adds a "source" field, label "Location" to the jdk.ClassDefine event. > > To enable this functionality, JFR needs a concurrent symbol table. We can build a simpler version of a concurrent hash table, taking advantage of the JFR epoch system. This will be useful also for planned future enhancements. > > Extensions are made to AOT to consistently report identical canonical paths for classes as non-AOT code paths. > > Testing: jdk_jfr, manual AOT verification, stress testing > > Thanks > Markus Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision: include apa ------------- Changes: - all: https://git.openjdk.org/jdk/pull/28505/files - new: https://git.openjdk.org/jdk/pull/28505/files/350203ca..af55c2a7 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=02 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=01-02 Stats: 4 lines in 2 files changed: 2 ins; 2 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/28505.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28505/head:pull/28505 PR: https://git.openjdk.org/jdk/pull/28505

1 0

Re: RFR: 8365400: Enhance JFR to emit file and module metadata for class loading [v2]
by Markus Grönlund 26 Nov '25

26 Nov '25

> Greetings, > > this enhancement adds a "source" field, label "Location" to the jdk.ClassDefine event. > > To enable this functionality, JFR needs a concurrent symbol table. We can build a simpler version of a concurrent hash table, taking advantage of the JFR epoch system. This will be useful also for planned future enhancements. > > Extensions are made to AOT to consistently report identical canonical paths for classes as non-AOT code paths. > > Testing: jdk_jfr, manual AOT verification, stress testing > > Thanks > Markus Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision: JFR_ONLY ------------- Changes: - all: https://git.openjdk.org/jdk/pull/28505/files - new: https://git.openjdk.org/jdk/pull/28505/files/2c6e4fb6..350203ca Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28505&range=00-01 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/28505.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28505/head:pull/28505 PR: https://git.openjdk.org/jdk/pull/28505

1 0

Re: RFR: 8365400: Enhance JFR to emit file and module metadata for class loading
by Coleen Phillimore 26 Nov '25

26 Nov '25

On Wed, 26 Nov 2025 12:10:55 GMT, Markus Grönlund <mgronlun(a)openjdk.org> wrote: > Greetings, > > this enhancement adds a "source" field, label "Location" to the jdk.ClassDefine event. > > To enable this functionality, JFR needs a concurrent symbol table. We can build a simpler version of a concurrent hash table, taking advantage of the JFR epoch system. This will be useful also for planned future enhancements. > > Extensions are made to AOT to consistently report identical canonical paths for classes as non-AOT code paths. > > Testing: jdk_jfr, manual AOT verification, stress testing > > Thanks > Markus Why did you write a different concurrent hash table? Why wasn't the existing one good enough? You say it's simpler but this adds many lines of code that someone has to read. src/hotspot/share/jfr/support/jfrSymbolTable.hpp line 68: > 66: > 67: void on_link(const Symbols::Entry* entry); > 68: void on_unlink(const Symbols::Entry* entry); What is Symbols ? Is it a JFR thing, so should it be JfrSymbols ? ------------- PR Review: https://git.openjdk.org/jdk/pull/28505#pullrequestreview-3510858860 PR Review Comment: https://git.openjdk.org/jdk/pull/28505#discussion_r2564923817

2 1

RFR: 8372441: JFR: Improve logging of TestBackToBackSensitive
by Erik Gahlin 25 Nov '25

25 Nov '25

Could I get a review of a PR that saves the dump file if a test fails? It also changes the order in which events are printed to make it easier to see in the log when chunk rotations happen. Testing: 1000 * jdk/jdk/jfr/event/runtom/TestBackToBackSensitive Thanks Erik ------------- Commit messages: - Initial Changes: https://git.openjdk.org/jdk/pull/28481/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28481&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8372441 Stats: 18 lines in 1 file changed: 9 ins; 6 del; 3 mod Patch: https://git.openjdk.org/jdk/pull/28481.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28481/head:pull/28481 PR: https://git.openjdk.org/jdk/pull/28481

2 2