Linux 中直接 I/O 机制的介绍
https://www.ibm.com/developerworks/cn/linux/l-cn-directio/index.html
深入浅出Linux】零拷贝技术sendfile
https://www.jianshu.com/p/028cf0008ca5
https://www.ibm.com/developerworks/cn/linux/l-cn-directio/index.html
https://www.jianshu.com/p/028cf0008ca5