I/O模型

class: center, middle

# I/O模型

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## 大纲

- 操作系统I/O模型分类
- 每种I/O模型在服务端的应用
- I/O模型的性能比较和发展

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## 同步阻塞I/O

![](http://my.csdn.net/uploads/201204/12/1334216532_9745.jpg)

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## 应用

- Rack CGI, Webrick

```ruby
TCPServer.open("127.0.0.1", 14641) {|server|
  s = server.accept
  s.puts Time.now
  s.close
}
```

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## 同步非阻塞I/O

![](http://my.csdn.net/uploads/201204/12/1334216607_3004.jpg)

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## 应用
```ruby
server = TCPServer.new(2202)
begin
  sock = server.accept_nonblock
rescue IO::WaitReadable, Errno::EINTR
  IO.select([server])
  retry
end
```

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## I/O 多路复用

![](http://my.csdn.net/uploads/201204/12/1334216620_6310.jpg)

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## 系统调用

* select/poll O(n)
* epoll/kqueue O(1)

- Nginx
- EventMachine
- Redis
- Node.js

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## Redis Reactor
![](http://1e-gallery.redisbook.com/_images/graphviz-3c09f0e53bd9d786aa646e5e4c289a11d97d40d7.png)

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## 信号驱动I/O
![](http://my.csdn.net/uploads/201204/12/1334216632_6025.jpg)

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## 异步I/O
![](http://my.csdn.net/uploads/201204/12/1334216641_7821.jpg)

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## AIO

- linux POSIX AIO: libeio, glibc libaio 
- windows IOCP
--
![](http://upload-images.jianshu.io/upload_images/1767848-e956abb035d567ec.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

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## nginx
![](http://cdn2.infoqstatic.com/statics_s2_20170620-0701/resource/articles/thread-pools-boost-performance-9x/zh/resources/0622006.jpg)

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## 比较

![](http://my.csdn.net/uploads/201204/12/1334216724_2405.jpg)

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## 网络库

- libevent : c
- libev : c++
- libuv : c++

## Ruby
- **EventMachine** : 自建
- **nio4r** : libev

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# 谢谢大家 Q&A