Somewhat amazed that this stuff _still_ isn't properly sorted out given that I was working on applications with a keen interest in the problem in 1996!!
NT's IO Completion Ports implemented some kind of CPU-balanced work delivery mechanism from the beginning, presumably inspired by Cutler's previous work on VMS's $QIO. AIX afaik also had something similar. Linux not so much...but in the intervening 20 years I had assumed epoll() was fixing this.
You assume things in Linux-land are "designed". It's more like natural evolution. It's very organic. As you'd expect, there's a lot of decomposition around. It kinda smells as you'd expect.
The Linux community is known to be infected with a drug-resistant strain of NIHV -- the Not Invented Here Virus. This means that if there's a thing like kqueue, or NT I/O Completion Ports, or Solaris Event ports, and Linux could copy and/or improve one (or more) of those, then you can count on Linux to invent a new thing that isn't as good as any of the others.
Perhaps some pharmaceutical will someday work on a treatment, cure, and/or vaccine for that strain of NIHV. More likely, the community will someday evolve resistance to NIHV, or else make NIHV moot by driving out all the competition.
The good news is that you can resist NIHV yourself. All you have to do is not believe that you alone can solve mankind's problems in a vacuum.
I don't remember it quite like that in this specific case. Rather I heard that there was push back against implementing a completion port model from somewhere (Redhat legal??) fearing patent action by MS. IBM had a mutual license agreement with MS I believe, which explains why AIX has something similar. The patents in question may even be in the set litigated over in the wake of Cutler moving to MS from DEC (which MS paid $$$ for and hence might be inclined to defend aggressively).
NT's IO Completion Ports implemented some kind of CPU-balanced work delivery mechanism from the beginning, presumably inspired by Cutler's previous work on VMS's $QIO. AIX afaik also had something similar. Linux not so much...but in the intervening 20 years I had assumed epoll() was fixing this.