[原]MINA的网络性能 - ReceiveBufferSize

E-Mail: basecn@163.com

首发地址:http://blog.csdn.net/basecn/archive/2010/10/12/5935289.aspx

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　　经过两天的测试发现，影响MINA网络性能的一个因素是她的ReceiveBufferSize。如果没有设置过，那么这个值默认是64K。

　　当发送小数据量时，这个参数没什么影响。如果发送大数据量，几百K或几兆时，通过观察ProtocolDecoder的doDecode方法，就会发现问题。

　　回过头先来看看doDecode方法，要求用户实现并返回boolean值。参考MINA的example可知，根据业务定义，当接收到的数据达不到预期时，应该返回false，这时MINA会尝试再次接收。

每次接收的量是多少呢？默认是64K，当设置receiveBufferSize大于64K时，新的receiveBufferSize才会生效，否则仍然使用64K做为接收缓冲。

　　OK，这样就可以知道，需要设置更大的receieBufferSize来增加接收缓存，以便一次性的接收更多的数据。

　　结果？还是不行！

　　最后找到的setReceiveBufferSize方法文档，这个方法是java.net.Socket的。MINA依赖的最底层的实现!

 

　　里面提到可以设置更大的值来提高大数据量的网络I/O性能，以减小往复读取的数据块。

　　在远端连接时，这个值也用来设置TCP接收窗口。

　　通常，窗口值可以在socket连接后的任何时间设置。然而，如果接收窗口大于64K时，远端需要在socket连接前设置这个值。

 

　　要注意下面两点：

　　1、  从ServerSocket接收socket时，要在ServerSocket绑定地址前调用 ServerSocket.setReceiveBufferSize(int)

　　2、  对于客户端，setReceiveBufferSize()要在连接前设置。

 

setReceiveBufferSize

public void setReceiveBufferSize(int size) throws SocketException

Sets the SO_RCVBUF option to the specified value for this Socket. The SO_RCVBUF option is used by the platform's networking code as a hint for the size to set the underlying network I/O buffers.

Increasing the receive buffer size can increase the performance of network I/O for high-volume connection, while decreasing it can help reduce the backlog of incoming data.

Because SO_RCVBUF is a hint, applications that want to verify what size the buffers were set to should callgetReceiveBufferSize().

The value of SO_RCVBUF is also used to set the TCP receive window that is advertized to the remote peer. Generally, the window size can be modified at any time when a socket is connected. However, if a receive window larger than 64K is required then this must be requested before the socket is connected to the remote peer. There are two cases to be aware of:

1.  For sockets accepted from a ServerSocket, this must be done by calling ServerSocket.setReceiveBufferSize(int) before the ServerSocket is bound to a local address.

2.  For client sockets, setReceiveBufferSize() must be called before connecting the socket to its remote peer.