Performance enhancement through simplicity
People have different views of how one should take performance measures while designing an application.
One approach is to think performance all the way. This means putting as much code in stored procedures as possible (most of what I do has a connection to a database), having denormalized data structures and generally focussing on the shortest execution path for everything. This approach makes sense because it directly confronts the problem.
It however has some problems which makes it suitable for only small projects. While being very simple with small applications the complexity grows a lot when the application grows a little. It has no focus on maintainability and can be a nightmare to fix later.
On the other side is the completely object oriented model. EJB is is an example of such an approach. In EJB (at least in the old version that I know) the programmer or designer lives in a happy cloud of ignorance towards performance. This is of course my interpretation of the framework. The fact is that the performance considerations in EJB lies in its scalability. All a matter of defining what performance is.
What I have concluded to my self is that performance is partly raw power, partly scalability but mostly simplicity by design.
By focussing on simplicity, it will be much easier to refactor those parts of your code that does not perform adequately. This is why I also consider OR mapping frameworks to be performance enhancing. They might not be directly performance enhancing, but they simplify the programs and make it possible to spend your time where it is more needed.