RFR: 8364090: Dump JFR recording on CrashOnOutOfMemoryError

[Erik Gahlin]

On Fri, 25 Jul 2025 08:05:03 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> src/hotspot/share/runtime/java.cpp line 466:
>> 
>>> 464:   }
>>> 465: 
>>> 466:   JFR_ONLY(Jfr::on_vm_shutdown(true, halt);)
>> 
>> You set oom to true here, why?
>
> To keep current behavior.
> 
> Before this change, 1st argument of `on_vm_shutdown` is `exception_handler`. You can see it on this change. If `exception_handler` sets to `false`, emergency dump handles it as OOM:
> 
> 
> static void post_events(bool exception_handler, Thread* thread) {
>   if (exception_handler) {
>     EventShutdown e;
>     e.set_reason("VM Error");
>     e.commit();
>   } else {
>     // OOM
>     LeakProfiler::emit_events(max_jlong, false, false);
>   }
>   EventDumpReason event;
>   event.set_reason(exception_handler ? "Crash" : "Out of Memory");
>   event.set_recordingId(-1);
>   event.commit();
> }
> 
> 
> I'm not sure this code would be called when OOM happens, but I think we need to keep this behavior in this change - this change focuses on working emergency dump with `CrashOnOutOfMemoryError`.

Could you call the parameter something more fitting? Perhaps emit_old_object_samples, if that is the new purpose of the flag?

I think the OldObjectSample event should only be emitted if an emergency dump occurs, preferably only on oom.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/26468#discussion_r2230486262