CSE403 Software Engineering Autumn 2001 Dead or Alive CSE 403 Autumn 2001 CSE403 Software Engineering Autumn 2001 Dead or Alive Gary Kimura Lecture #24 November 28, 2001 November 28, 2001

Today Be careful with what you say and do Finish with “when to call it a day” Is the system dead or alive?

Dead or just slow How do you tell if a system is really dead or just show? Some cases are really obvious Bugcheck (the window’s blue screen of death) Slowly drawing a new screen Slowly making progress But some cases are less obvious A struck mouse or one that moves slowly Non responsive to Ctrl-C A pegged CPU metter A disk that is being pounded upon Distributed application are even harder to diagnose

Who cares From a developer viewpoint does it really matter if a system is slow? From a customer viewpoint does it really matter if a system is slow versus dead? And how would the customer tell the two apart?

Where to look for solutions in slow systems Infinite loops Thrashing Beware of secondary processes that are chewing up all the resources. Priority inversion makes some systems look pretty dead Illegal process state

Beyond our control What if the fix is beyond the developers control? What if the customer is too cheap to buy faster larger machines?