RFR: 8368159: Significant performance overhead when started with jdwp agent and unattached debugger [v2]

[Serguei Spitsyn]

On Wed, 24 Sep 2025 22:06:29 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>>> But if we are not in interp_only mode isn't it already invalidated?
>> 
>> It does not need to be invalidated if not in `interp_only` mode as it should not be used there or has to be explicitly invalidated exactly where it is needed (the frame pops cleaning code for plain Continuations). The issue I see is only with the test `test/hotspot/jtreg/serviceability/jvmti/vthread/ContStackDepthTest` which is for plain Continuations. Otherwise, the `invalidate_jvmti_stack()` would not be needed. It plays as a workaround to make this test to pass. It seems there is a bug related to plain Continuations lurking somewhere.
>
> My point is we could just unconditionally invalidate. It would do no harm. It would not be invalidating a curr stack depth that could later be used.

Okay, thanks! I'll make it unconditional. I do not see any performance degradation with that. Also, it will keep the `test/hotspot/jtreg/serviceability/jvmti/vthread/ContStackDepthTest` test passed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27403#discussion_r2377332233