RFR: 8360025: (se) Convert kqueue Selector Implementation to use FFM APIs [v2]

[ExE Boss]

On Tue, 19 Aug 2025 13:18:49 GMT, Darragh Clarke <dclarke at openjdk.org> wrote:

>> This PR aims to Panamize the Java Kqueue implementation, This is based on the work that was previously shared in https://github.com/openjdk/jdk/pull/22307 , The main change since then is that this branch takes advantage of the changes made in https://github.com/openjdk/jdk/pull/25043 to allow for better performance during errno handling.
>> 
>> These changes feature a lot of Jextract generated files, though alterations have been made in relation to Errno handling and performance improvements.
>> 
>> I will update this description soon to include performance metrics on a few microbenchmarks, though currently it's roughly 2% to 3% slower with the changes, which is somewhat expected, though there are still a few ideas of possible performance improvements that could be tried. Any suggestions or comments in that area are more than welcome however.
>
> Darragh Clarke has updated the pull request incrementally with one additional commit since the last revision:
> 
>   implementing feedback, adding missing errno checks, cleanup

src/java.base/macosx/classes/sun/nio/ch/KQueuePoller.java line 50:

> 48:                     "kqueue failed");
> 49:         }
> 50:         this.kqfd = res;

Maybe this duplicated check should probably be moved into a common method in `KQueue`, like the old `KQueue.create()` method, but implemented in **Java**:

static int create() throws IOException {
	int res = kqueue_h.kqueue();
	if (res < 0) {
		throw ErrnoUtils.IOExceptionWithErrnoString(-res, "kqueue failed");
	}
	return res;
}

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/25546#discussion_r2285879853