RFR: 8342818: Implement CPU Time Profiling for JFR

[Johannes Bechberger]

On Wed, 30 Oct 2024 08:58:17 GMT, Jaroslav Bachorik <jbachorik at openjdk.org> wrote:

>> What else should I use? I want to check for the adaption of the sampling period every few seconds.
>
> Perhaps `os::javaTimeNanos()` would be better? It provides global monotonic time.
> OTOH, `os::javaTimeMillis()` can move unexpectedly - a good example is the daylight saving time where the millis would suddenly jump 1 hour to the past.

Good point, I totally forgot about the monotonicity.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20752#discussion_r1822176104