Epoll_native non-blocking transport for Linux
As we explained earlier, Netty’s NIO transport is based on the common abstraction for
asynchronous/non-blocking networking provided by Java. Although this ensures that
Netty’s non-blocking API will be usable on any platform, it also entails limitations,
because the JDK has to make compromises(妥协，折中) in order to deliver the same capabilities on all systems.
The growing importance of Linux as a platform for high-performance networking
has led to the development of a number of advanced features, including epoll, a highly
scalable I/O event-notification feature. This API, available since version 2.5.44 (2002)
of the Linux kernel, provides better performance than the older POSIX select and
poll system calls and is now the defacto(事实上的) standard for non-blocking networking on
Linux. The Linux JDK NIO API uses these epoll calls.
Netty provides an NIO API for Linux that uses epoll in a way that’s more consistent
with its own design and less costly in the way it uses interrupts.
Consider utilizing(利用，使用) this version if your applications are intended for Linux; you’ll find that performance under heavy load is superior to that of the JDK’s NIO implementation.
The semantics of this transport are identical to those shown in figure 4.2, and its
use is straightforward. For an example, refer to listing 4.4. To substitute(代替，替换) epoll for NIO
in that listing, replace NioEventLoopGroup with EpollEventLoopGroup and NioServerSocketChannel.class with EpollServerSocketChannel.class.