为什么Nginx的性能要比Apache高很多？

几乎所有的epoll程序都使用下面的框架：

• for( ; ; )
      {
          nfds = epoll_wait(epfd,events,20,500);
          for(i=0;i<nfds;++i)
          {
              if(events[i].data.fd==listenfd) //有新的连接
              {
                  connfd = accept(listenfd,(sockaddr *)&clientaddr, &clilen); //accept这个连接
                  ev.data.fd=connfd;
                  ev.events=EPOLLIN|EPOLLET;
                  epoll_ctl(epfd,EPOLL_CTL_ADD,connfd,&ev); //将新的fd添加到epoll的监听队列中
              }
              else if( events[i].events&EPOLLIN ) //接收到数据，读socket
              {
                  n = read(sockfd, line, MAXLINE)) < 0    //读
                  ev.data.ptr = md;     //md为自定义类型，添加数据
                  ev.events=EPOLLOUT|EPOLLET;
                  epoll_ctl(epfd,EPOLL_CTL_MOD,sockfd,&ev);//修改标识符，等待下一个循环时发送数据，异步处理的精髓
              }
              else if(events[i].events&EPOLLOUT) //有数据待发送，写socket
              {
                  struct myepoll_data* md = (myepoll_data*)events[i].data.ptr;    //取数据
                  sockfd = md->fd;
                  send( sockfd, md->ptr, strlen((char*)md->ptr), 0 );        //发送数据
                  ev.data.fd=sockfd;
                  ev.events=EPOLLIN|EPOLLET;
                  epoll_ctl(epfd,EPOLL_CTL_MOD,sockfd,&ev); //修改标识符，等待下一个循环时接收数据
              }
              else
              {
                  //其他的处理
              }
          }
•     }