You have different options. What is you OS? You can use FULLSTIMER a general suggestion and also, look up ARM monitoring form the online help. That allows you very specific and precise induction points.
You can also place (quick and dirty) start and elapsed time at different intervals in your logs (not good method). If you are on UNIX, depending which flavor you can use vendor provided tools, such as GLM (for HP), etc.
HTH
Rafi