Focusing on what they see and not on what the problem actually is
Performance problems are mainly seen only in production, but they can be understood only in development. However, in many cases, when a problem arises in the development, the developers are focusing on what they see (their own code) and not focusing completely on what the problem actually is. It is important that the performance problem be approached from the system point of view.
Unfortunately, many times, optimizing of the code is done in an ad-hoc manner – and many times this is done just because there is an unproven assumption that a certain piece of code might be slow.
Performance problems and data are rarely published in a manner that makes it possible for developers, support personnel or customers to work on it. Even if the data is published, it is usually in a convoluted form as a confusing excel spreadsheet with zillions of numbers, or published as a marketing fuzz without meaningful data. A well-organized technical document outlining performance problems, known solutions and possible solutions is a much more effective and efficient method to arrive at the proper solution for a specific performance issue.