Re: kqueue backend for pgbench

Hi! Thanks for the review!

> Another solution to this is to have code which does not use fd_set but instead uses its own method of building and using bit arrays. I have done this in my professional development.
> I'll include the NOTES from Freebsd on the select(2) man page....
>

I rechecked the docs and the kernel impl example [0].
There is some thought about I thinking:
- max absolute fd number will be limited by FD_SETSIZE, which is
defined at compile time, would it be a fragile solution for runtime anyway?
The the implementation of bit string must rely on architecture-depended things
(ex: _DARWIN_UNLIMITED_SELECT), which will lead to a patch
similar in size to the proposed?
- the cost of operations will have O(max_fd) instead of O(nfd),
which is not critical for current implementation of pgbench, but in future may
lead to refactor of struct socket_set or the code below
- kevent already used in backend code base for cases of several fds,
proposed patch would be just continuation of [1] which have same style
to waiteventset.c

[0] - https://elixir.bootlin.com/freebsd/v15.1/source/sys/kern/sys_generic.c#L1189
[1] - https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=60e612b602999e670f2d57a01e52799eaa903ca9

--
Best regards,
Roman Khapov