RFR: 8310994: Add JFR event for selection operations [v6]

[Alan Bateman]

On Wed, 10 Apr 2024 23:51:34 GMT, Tim Prinzing <tprinzing at openjdk.org> wrote:

>> Added mirror event with static methods: jdk.internal.event.SelectionEvent that provides the duration of select calls and the count of how many keys are available.
>> 
>> Emit the event from SelectorImpl::lockAndDoSelect
>> 
>> Test at jdk.jfr.event.io.TestSelectionEvents
>
> Tim Prinzing has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove selector spin event attempt and associated test.

src/jdk.jfr/share/classes/jdk/jfr/events/SelectorSelectEvent.java line 40:

> 38: 
> 39:     @Label("SelectionKey Count")
> 40:     @Description("Number of channels ready for I/O or added to ready set")

We'll need to give you a better description for this. The value is the number of selection keys were updated by the selection operation. In many usages this will be the same as the number of keys added to the selected-key set (not "ready set") but they can be different.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16710#discussion_r1560501216