Performance Goals

Performance Goals

Given this general understanding of Web services based on .NET, what becomes obvious is that the expeditious delivery of these services to devices any time and anywhere is critical. There are many aspects to performance but the most important from the ACE team perspective is increasing performance by reducing end user response time bottlenecks. Optimizing user response times is our top goal because the response time is the only performance metric to which the users are directly exposed. Scalability and availability are important inputs to optimal response times and these will be discussed in detail. Just because the user does not see them, does not diminish their importance. Without adequate scalability and availability, the application response times will obviously suffer. Ultimately though, application responsiveness is the critical component that will determine success or failure with the customer in the performance game.

Computer Interaction Behavioral Patterns

Despite the relatively recent rise in Internet usage during the last decade, computer interaction response time studies have been around since the advent of the computer. Research indicates that users interact with a computer to perform a task. According to an article titled Response Time In Man-Computer Conversational Transactions, written in 1968 by R.B. Miller for the AFIPS Fall Joint Computer Conference, Vol. 33, 267-277, the computer user will react to response time performance in predictable behavioral patterns similar to those listed here:

• 0.1 second

  is the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result.

• 1.0 second

  is the limit for the user s flow of thought to stay uninterrupted, even though the user will notice the delay. Normally, no special feedback is necessary during delays of more than 0.1 but less than 1.0 second, but the user does lose the feeling of operating directly on the data.

• 10 seconds

  is the limit for keeping user attention focused on the screen dialogue. For longer delays, users will want to perform other tasks while waiting for the computer to finish, so they should be given feedback indicating when the computer is likely to be done. Feedback during the delay is especially important if the response time is likely to be highly variable, since users will then not know what to expect.

When measuring response times, it might become apparent that the root cause for the high response times could be beyond your control, making it impossible to attain one-tenth of a second times. For example, there really is not a lot that can be done about Internet congestion or a slow client dial-up connection. Nevertheless, it is still necessary to understand the root cause of the high response times, to make an impact wherever possible. The goal of this book is to lay out a reliable methodology for identifying this cause, otherwise known as the bottleneck, and subsequently addressing that bottleneck in such a manner that it results in improved application performance. This book will hopefully serve as proof that proper performance testing and tuning methodologies integrated into the software development life cycle can result in sub-second response times for the resultant .NET application.