enable_tracer_by_name
retval = enable_tracer_by_name(trace_inst->inst, ops->tracer);
retval = enable_tracer_by_name(trace->trace.inst, tracer);
retval = enable_tracer_by_name(tool->aa->trace.inst, "timerlat");
int enable_tracer_by_name(struct tracefs_instance *inst, const char *tracer_name);