RFR: 8352251: Implement JEP 518: JFR Cooperative Sampling [v23]

[Patricio Chilano Mateo]

On Fri, 16 May 2025 00:01:14 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>>> Another case we are missing is when we freeze. We should call `Jfr::check_and_process_sample_request` before copying the frames to the heap.
>> 
>> Where do you suggest to place it best?
>
> Thanks. So if we create the request as mentioned before I’m not sure that check will do it. I see it’s checking for enterSpecial instead of its caller. Also I see we only get there in the interpreted case, but the caller of enterSpecial could be compiled. I was thinking of an early check where if we are in a vthread and the sample request is not within the continuation just do a bias sampling.

> Where do you suggest to place it best?
>
Should be in `FreezeBase::unwind_frames()`. That's where we change the anchor to the ContinuationEntry.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/24296#discussion_r2092120587