RFR: 8351999: JFR: Incorrect scaling of throttled values

[Aleksey Shipilev]

On Fri, 14 Mar 2025 01:52:15 GMT, Erik Gahlin <egahlin at openjdk.org> wrote:

> Could I have a review of a PR that fixes an incorrect scaling of samples for the ThrottleSetting.
> 
> Testing: jdk/jdk/jfr
> 
> Thanks
> Erik

Marked as reviewed by shade (Reviewer).

src/jdk.jfr/share/classes/jdk/jfr/internal/settings/ThrottleSetting.java line 97:

> 95:             if (unit.nanos < SECONDS.nanos) {
> 96:                 long perSecond = SECONDS.nanos / unit.nanos;
> 97:                 samples = Utils.multiplyOverflow(samples, perSecond, Long.MAX_VALUE);

Reasoning from the math alone, it looks obvious that `samples *= samples` is not correct. So that part looks fine.

Thinking about `unit.nanos == SECONDS.nanos` case. This means the unit is exactly "seconds", so no adjustment is needed?

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PR Review: https://git.openjdk.org/jdk/pull/24045#pullrequestreview-2685332765
PR Review Comment: https://git.openjdk.org/jdk/pull/24045#discussion_r1995449423