Epoll analysis

epoll It is the kernel that provides user process calls , Need to understand epoll What problem to solve . In the absence of epoll Before , The user process needs to know something socket Is there any data coming , It needs to be called once recev function . This is an interrupt handling from the user process to the kernel , It has little impact on scenes with a small number of links , If the current server has 10000 Links . Even if only 1 Links have data coming , But the user process will call once for each connection , That is to say, it is necessary to switch between user processes and kernel processes 10000 times , Performance is affected . and epoll Is an interface provided by the kernel to the user process , The user only needs to call... Once , You can return the link with data to the user process , In this way, the user only needs to deal with the data coming to the link .