most of its time. Many factors can easily give misleading or temporarily different measurements to the application. Distributed garbage collection may have cut in, system clocks may become unsynchronized, background processes may be triggered, and relative processor power may change, causing obscure effects. Consider if anyone else is using the processors, and if so, what they are doing and why.
O’reilly - Java Performance Tuning - 301 - You need to differentiate between: • Occasional sudden slowness, e.g., from background processes starting up • General slowness, perhaps reflecting that the application was not tuned for the current load, or that the systems or networks are saturated • A sudden slowdown that continues, often the result of a change to the system Each of these characteristic changes in performance indicate a different set of problems. 13.6 More Factors That Affect Performance The following sections discuss some aspects of the application that may not immediately strike you as part of the performance of the application. But they do affect the user's perception of the application performance, and so are relevant. 13.6.1 User Interface Usability The application's user interface has a significant effect on the user's perception of performance. The time required to navigate through the user interface to execute some functionality is seen by the user as part of the application's response time. If window and menu navigation is difficult, performance is seen to be bad (and actually, it is bad). The user interface should support the natural flow of the user's activity; otherwise, you are forcing the user to perform less efficiently. Improving only the navigability of the user interface, even with no other changes to the application, improves the perceived performance of an application. 13.6.2 Training Training users to use the application is also a performance issue. Without proper training, users may not use the application efficiently, and will then compare the application unfavorably with another application they are comfortable with. Since they are comparing similar functionality, the user immediately focuses on the differences. The main difference, of course, is the perceived performance. The user never thinks he is untrained. He simply feels that executing some function in your application takes forever, as he stumbles through menu options trying to find what he wants, fills in forms incorrectly, etc. The result is a perception of bad performance. Note that making help desks available is an essential part of the training program. Training is seldom so thorough that all parts of the application are covered in enough detail, and it is also common for people to forget some of their training. A help desk keeps the users from getting lost and giving up on the most efficient route to solve their tasks.
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