RFR: 8310994: Add JFR event for selection operations [v3]

[Alan Bateman]

On Wed, 13 Dec 2023 22:20:55 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:
> 
>   add select timeout field to the event

src/java.base/share/classes/sun/nio/ch/SelectorImpl.java line 143:

> 141:         throws IOException
> 142:     {
> 143:         // filter selectNow ops from consideration (timeout == 0)

I think simplify this comment to say no JFR event for selectNow.

src/java.base/share/classes/sun/nio/ch/SelectorImpl.java line 153:

> 151:         if ((n == 0) || (SelectorSelectEvent.shouldCommit(duration))) {
> 152:             timeout = (timeout < 0) ? 0 : timeout;
> 153:             SelectorSelectEvent.commit(start, duration, n, timeout);

The comment is a bit confusing here.  n == 0 means that no selected keys were added or consumed before timeout or wakeup.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16710#discussion_r1440332584
PR Review Comment: https://git.openjdk.org/jdk/pull/16710#discussion_r1440332569