RFR: JDK-8263426: Reflow JfrNetworkUtilization::send_events

[Markus Grönlund]

On Thu, 11 Mar 2021 09:32:58 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> SonarCloud instance reports a problem in JfrNetworkUtilization::send_events: "Identical sub-expressions on both sides of operator "-"." here:
> 
>   const JfrTickspan interval = last_sample_instant == 0 ? cur_time - cur_time : cur_time - last_sample_instant;
> 
> Note `cur_time - cur_time`. It would seem that `interval` is effectively zero when `last_sample_instant` is not yet initialized. And I see that the subsequent code checks for `interval.value() > 0` for every interface. That can be optimized a bit: when `last_sample_instant` is not available, do not enter the loop, and don't check `interval.value()`.
> 
> Additional testing:
>  - [x] `jdk_jfr` on Linux x86_64

Looks good, thanks.

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Marked as reviewed by mgronlun (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2935