On Fri, 22 May 2026 09:47:16 GMT, Serguei Spitsyn <[email protected]> wrote:
>> This change fixes a long standing performance issue related to the debugger >> single stepping that is using JVMTI `FramePop` events as a part of step over >> handling. The performance issue is that the target thread continues its >> execution in very slow `interp-only` mode in a context of frame marked for >> `FramePop` notification with the JVMTI `NotifyFramePop`. It includes other >> method calls recursively upon a return from the frame. >> >> This fix is to avoid enforcing the `interp-only` execution mode for threads >> when `FramePop` events are enabled with the JVMTI >> `SetEventNotificationMode()`. Instead, the target frame has been deoptimized >> and kept interpreted by disabling `OSR` optimization by the function >> `InterpreterRuntime::frequency_counter_overflow_inner()`. (Big thanks to >> @fisk for this suggestion!) Additionally, some tweaks are applied in several >> places where the `java_thread->is_interp_only_mode()` is checked. >> The other details will be provided in the first PR request comment. >> >> Testing: >> - test `serviceability/jvmti/vthread/ThreadStateTest` was updated to >> provide some extra test coverage >> - submitted mach5 tiers 1-6 >> >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Serguei Spitsyn has updated the pull request incrementally with one > additional commit since the last revision: > > review: 1. Add asserts, rem comment 2. Remove can_generate_frame_pop_events > from can_generate_interpreter_events Hi, I checked it with the simple artificial example from [IDEA-292196](https://youtrack.jetbrains.com/issue/IDEA-292196) public static void main(String[] args) { int x = foo(); // add a breakpoint here and do step over System.out.println(x); } Here are the results: It took 3ms - No stepping, just a breakpoint on the line with println and resume It took 50045ms - jdk 25 It took 15686ms - jdk 27 Build 28 (2026/6/25) So the stepping speedup looks significant! ------------- PR Comment: https://git.openjdk.org/jdk/pull/28407#issuecomment-4831003214
