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BSD kqueue is a mountain of technical debt (2021)

A side effect of the whole freenode kerfluffle is that I’ve been looking at IRCD again. IRC, is of course a very weird and interesting place, and the smaller community of people who run IRCDs are largely weirder and even more interesting. However, in that community of IRCD administrators there happens to be a few incorrect systems programming opinions that have been cargo culted around for years.

This is naturally a lot more efficient than select, where you have to iterate over all file descriptors up to fdmax and test for membership in each of the three bitmaps to ascertain each socket’s status. The kqueue syscall creates a handle in the kernel represented as a file descriptor, which a developer uses with kevent to add and remove event filters. In general, the scalability aspects are the same to the application programmer: you have your sockets, you use epoll_ctl to add them to the kernel’s epoll handle, and then you wait for events, just like you would with kevent.

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