The future of fd stateful monitoring / eventing in Haiku

[kallisti5]

Today Haiku offers a "wait_for_objects" API (stateless) which is as close as we get to epoll / kqueue which exists on OS X / FreeBSD / Linux.

Pulkomandy pointed out a great overview here:

​https://fosdem.org/2021/schedule/event/file_descriptor_monitoring/

... and some previous work around event polling here:

​https://github.com/hamishm/haiku/tree/eventqueue

A good model would likely be:

1. Implement a fairly standard/complete io_uring (fd and sockets)
2. Add epoll/kqueue compatibility functions which silently leverage io_uring
3. Drop wait_for_objects or make it official. (only consumer seems to be power daemon ​https://git.haiku-os.org/haiku/tree/src/servers/power/power_daemon.cpp#n118)

That video mentions performance improvements at large scale for things leveraging epoll/kqueue/io_uring over the POSIX poll/select