[mikekchar]

Possibly a subtitle: It's never what you think it is. I've worked in embedded and real time environments before and optimisation used to be my thing, but I am always surprised at how badly I guess what the problem is. It's a hard lesson to teach other people though because programmers are smart and smart people tend to default to thinking that they are correct :-)

But you are right: even when you isolate where the code is slow, you've still got a lot of work to do to find out why it is slow.