https://idndx.com/2014/09/01/the-implementation-of-epoll-1/
https://idndx.com/2014/09/02/the-implementation-of-epoll-2/
https://idndx.com/2014/09/22/the-implementation-of-epoll-3/
https://idndx.com/2015/07/08/the-implementation-of-epoll-4/
https://www.quora.com/Network-Programming-How-is-epoll-implemented
https://www.kernel.org/doc/ols/2004/ols2004v1-pages-215-226.pdf
http://man7.org/linux/man-pages/man7/epoll.7.html
http://blog.163.com/huchengsz@126/blog/static/73483745201181824629285/
原文：https://www.cnblogs.com/WCFGROUP/p/9390094.html