1. 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

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

3. 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

4. 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?

5. 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

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