Performance tuning in an agile world...

I have taken over the lead on the performance tuning of our application.

A few interesting notes on performance tuning:

1) We do performance tuning test first.

We use Watir to drive our performance tests - because they reflect the experience of the user. We can measure the responsiveness of the app. Also we get to show the users what we are measureing and see if it matches their workflow in a month

On our project, we have moved away from the traditional pass/fail test for performance. We have red, yellow and green. Green means we're with in our target, yellow indicates we're within about 50% and red, well, we're in trouble. It helps prioritize our work.

As always we're running these tests a few time a day in a cruise-control like process.

2) There are different areas of performance tuning.

We have GUI response time, processing time and import/export time (our application has a large component of reporting and third party application interaction in it).

We concentrate on each one, writing tests and getting feedback from our testers on how the system is doing.

3) Break down the problem. Tackle one thing at a time to make it managable.

Performance, Load, Concurrency are all heavily interrealted problems. The nice thing is that we can takle them individually, we don't have to deal with them all at once.

We use both real and imaginary data to drive our performance tests (Actually, we use real data that are part of our regression suite).

4) Thank god that your developers have been refactoring code. You'll notice when you have some "original" design code, versus stuff that has been worked over. It is way easier to tune the latter.