netty为什么提供EpollEventLoopGroup？

Question

经过我的测试，Netty的

NioEventLoopGroup

和

EpollEventLoopGroup

在性能上没有区别。为什么Netty也提供了EpollEventLoopGroup？

当服务器维护1000个TCP链接时，服务器的CPU和内存没有区别。这是我的代码：

public class EpollServer {
        public static void main(String[] args) throws Exception {
            logger.info("port:"+System.getProperty("port", "8007"));
            logger.info("isUseEpoll:"+System.getProperty("isUserEpoll","true"));
            EventLoopGroup bossGroup;
            EventLoopGroup workerGroup;
            Class          clazz;
    
            if (useEpoll()) {
                bossGroup = new EpollEventLoopGroup(1);
                workerGroup = new EpollEventLoopGroup();
                clazz = EpollServerSocketChannel.class;
            }else{
                bossGroup = new NioEventLoopGroup(1);
                workerGroup = new NioEventLoopGroup();
                clazz = NioServerSocketChannel.class;
            }
    
            final EpollServerHandler epollHandler = new EpollServerHandler();
            try {
                ServerBootstrap b = new ServerBootstrap();
                logger.info("[socket Type]: {}", clazz.getSimpleName());
                b.group(bossGroup, workerGroup)
                        .channel(clazz)
                        .option(ChannelOption.SO_BACKLOG, 10001)
                        .childHandler(new ChannelInitializer<SocketChannel>() {
                            @Override
                            public void initChannel(SocketChannel ch) throws Exception {
                                ChannelPipeline p = ch.pipeline();
                                p.addLast(new LengthFieldBasedFrameDecoder(1024,0,2,0,2));
                                p.addLast(new SimpleChannelInboundHandler(){
                                    @Override
                                    protected void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
                                        ByteBuf content = (ByteBuf) msg;
                                        ctx.channel().writeAndFlush(content.retain());
                                    }
                                });
    
                            }
                        });
   
                ChannelFuture f = b.bind(PORT).sync();
                f.channel().closeFuture().sync();
            } finally {
                bossGroup.shutdownGracefully();
                workerGroup.shutdownGracefully();
            }
        }


    private static boolean useEpoll() {
        if(isUseEpoll){
            return Epoll.isAvailable();
        }else{
            return false;
        }
    }
}

Answer 1

我可以告诉你，在“重负载”场景中，肯定存在以下性能差异：

• CPU 使用率
• 内存使用
• 分配

除此之外，原生 epoll 传输还支持 NIO 本身未公开的多种功能。