顾名思义，buffer 就是缓存了。 如果你想对 IO 性能进行调整，就可以自己指定缓存大小。

http://en.wikipedia.org/wiki/Data_buffer

#2 楼 @hooopo 多谢 Buffers are typically used when there is a difference between the rate at which data is received and the rate at which it can be processed, or in the case that these rates are variable, for example in a printer spooler or in online video streaming.