RFR: 8364638: Refactor and make accumulated GC CPU time code generic [v5]

[Stefan Johansson]

On Thu, 14 Aug 2025 13:07:07 GMT, Jonas Norlinder <duke at openjdk.org> wrote:

>>> ... it might happen from time to time without it being a very big deal?
>> 
>> My concern is that we get a number on cpu-time without knowing the number is off by a large margin when failure occurs, so there should probably be some warning/msg somewhere.
>
> I don't sample GC threads that have terminated, so I would prefer not having the warning as well, as it would not fail unless the machine is in a bad state and then we would have larger issues at hand anyways?

> My concern is that we get a number on cpu-time without knowing the number is off by a large margin when failure occurs, so there should probably be some warning/msg somewhere.

Sure, that could be helpful. I don't think it should be a warning on the OS API though. Looking at the code a log message like that could be added to `CPUTimeThreadClosure::do_thread(...)`. To me it would be enough to have that on `log_info(cpu)` possibly even on debug-level. What do you think?

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PR Review Comment: https://git.openjdk.org/jdk/pull/26621#discussion_r2278420082