reference
- http://www.pudn.com/Download/item/id/3307884.html
- https://www.zhihu.com/question/19606660
- https://zhuanlan.zhihu.com/kernel
- https://www.quora.com/profile/Robert-Love-1
- https://www.ibm.com/developerworks/cn/linux/l-adfly/index.html
- https://www.ibm.com/developerworks/cn/linux/l-linux-kernel/index.html#artrelatedtopics