RFR: 6960970: Debugger very slow during stepping [v2]
Serguei Spitsyn
sspitsyn at openjdk.org
Thu Nov 20 04:45:24 UTC 2025
> 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 enabling the `interp-only` mode for threads when `FramePop` events are enabled with JVMTI `SetEventNotificationMode`. Instead, the target frame has been deoptimized and kept interpreted by disabling `OSR` in the function `InterpreterRuntime::frequency_counter_overflow_inner()`. 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.
> It is considered to file a SCR for this update a `FramePop` events do not enforce the `interp-only` mode for a target thread anymore which might break some expectations (the behavior has been changed).
>
> Testing:
> - test `serviceability/jvmti/vthread/ThreadStateTest` was updated to provide some extra test coverage
> - submitted mach5 tiers 1-6
Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
cleanup: removed an old code fragment in frame.cpp
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/28407/files
- new: https://git.openjdk.org/jdk/pull/28407/files/d31aefb6..b3cffe5a
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=28407&range=01
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=28407&range=00-01
Stats: 14 lines in 1 file changed: 0 ins; 14 del; 0 mod
Patch: https://git.openjdk.org/jdk/pull/28407.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/28407/head:pull/28407
PR: https://git.openjdk.org/jdk/pull/28407
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