time clock getrusage clock_gettime gettimeofday timespec_get 对比
http://stackoverflow.com/questions/12392278/measure-time-in-linux-time-vs-clock-vs-getrusage-vs-clock-gettime-vs-gettimeof
+V why_null 请备注:from博客园
http://stackoverflow.com/questions/12392278/measure-time-in-linux-time-vs-clock-vs-getrusage-vs-clock-gettime-vs-gettimeof
+V atob('d2h5X251bGw=')
请备注:from博客园