Lets be honest, most software that developers produce has quite modest performance requirements. E.g. Systems perhaps serving 100's of requests per second, if that.

But lets assume for a moment (or even dream) that you where perhaps involved in the "next big thing" (whatever that means) and you wanted to put some sort of performance statistics logging in place to help you out when all those users come flying in.

Performance statistics logging, how would you approach this requirement? Perhaps you would use some sort of generic framework for this? Or roll your own solution? What would you log? How granular?

Or would you not even bother putting anything in place and rather deal with this issue when it actually became an issue?

It would be really interesting to hear your thoughts on this topic.