Performance Guide
Chapter 2, Managing performance

Chapter 2

Chapter 2<P> Managing performance Managing performance

To manage the performance of a system, you normally try to share the available resources equally between its users. However, different users perceive performance according on their own needs and the demands of the applications that they are running. If they use interactive programs, response time is likely to be their main index of performance. Someone interested in performing numeric analysis may only be worried about the turnaround time for off-line batch mode processing. Another person may wish to perform sophisticated image processing in real time and requires quick access to graphics data files. You, as the administrator, are interested in maximizing the throughput of all jobs submitted to the system -- in fact, keeping everyone happy. Unfortunately, such differing requirements may be difficult to reconcile.

For example, if you administer a single standalone system, you may decide that your main priority is to improve the interactive response time. You may be able to do this by decreasing the overall workload at peak usage times. This would involve scheduling some work to run as batch jobs at quieter times, or perhaps restricting simultaneous access to your system to a smaller number of users. However, in speeding up your system's response you now have the additional problem of decreased throughput, which results in the completion of fewer jobs, potentially at critical times. In pursuing any particular performance improvement policy there are always likely to be trade-offs, especially in a situation where resources are at a premium.

The next section covers the setting of realistic performance goals as the first step in improving the performance of your computer system. You are then given a method for observing and tuning a system.