The accepting socket is shared between multiple workers which each have its own fd for epoll or kqueue. Because of this a form of serialising the accepts between said workers is needed to avoid unnecessary wakeups.
If you are the author, thanks for sharing the project. You did a great job and made the right choice of having per CPU worker processes each with their own epoll loop.
http://lwn.net/Articles/633422/
See part about EPOLLEXCLUSIVE