Thanks a lot. So far is so good for me. But I am also thinking about a feature in trace event definition. There is a parameter in TRACE_EVENT, which opts for whether this trace is taken at the start and end of the tracing (just like what I wanted). And a default trace info. Maybe others also need this. Yuyang -- To unsubscribe from this list: send the line "unsubscribe linux-trace-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html