使用时间标记服务分两步，第一步调用alt_timestamp_start()开启时间标记服务，第二步调用alt_timestamp()测量用户感兴趣的时间点。还有一个函数alt_timestamp_freq(),调用之后可以获得系统工作频率-Use time-stamping services in two steps, first call alt_timestamp_start () open the time-stamping services, the second step calls alt_timestamp () measurement time points of interest to users. There is also a function alt_timestamp_freq (), call to get the system working frequency after