There are various ways to look at performance. You can look at user experience, generate load similar to what application usage produces or you can do more basic things like query performance. What will you be looking at? Resource consumption and throughput are the usual suspects.
I'll look at a simple example in this blog post. I'll change database parameters and look at throughput of various actions which are regularly performed on databases. This takes away the complexity of distributed systems. I used a single Python script for this which can be downloaded here.