Performance Tools Guide and Reference

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Performance tuning on a new system involves setting base parameters for the operating system and its applications. The CPU Utilization Reporting Tool (curt), Simple performance lock analysis tool (splat), and procmon tool allow for optimal performance tuning.

The path to achieving this objective is a balance between appropriate expectations and optimizing the available system resources. The performance-tuning process demands great skill, knowledge, and experience, and cannot be performed by only analyzing statistics, graphs, and figures. If results are to be achieved, the human aspect of perceived performance must not be neglected. Performance tuning also takes into consideration problem-determination aspects as well as pure performance issues.

Expectations can often be classified as either of the following:

Item	Descriptor
Throughput expectations	A measure of the amount of work performed over a period of time
Response time expectations	The elapsed time between when a request is submitted and when the response from that request is returned

The performance-tuning process can be initiated for a number of reasons:

To achieve optimal performance in a newly installed system
To resolve performance problems resulting from the design (sizing) phase
To resolve performance problems occurring in the run-time (production) phase

Performance tuning on a newly installed system usually involves setting some base parameters for the operating system and applications. Throughout this book, there are sections that describe the characteristics of different system resources and provide guidelines regarding their base tuning parameters, if applicable.

Limitations originating from the sizing phase will either limit the possibility of tuning, or incur greater cost to overcome them. The system might not meet the original performance expectations because of unrealistic expectations, physical problems in the computer environment, or human error in the design or implementation of the system. In the worst case, adding or replacing hardware might be necessary. Be particularly careful when sizing a system to permit enough capacity for unexpected system loads. In other words, do not design the system to be 100 percent busy from the start of the project.

When a system in a productive environment still meets the performance expectations for which it was initially designed, but the demands and needs of the utilizing organization have outgrown the system's basic capacity, performance tuning is performed to delay or even to avoid the cost of adding or replacing hardware.

Many performance-related issues can be traced back to operations performed by a person with limited experience and knowledge who unintentionally restricted some vital logical or physical resource of the system.

Note: The metrics reported by any statistics tool such as lparstat, vmstat, iostat, mpstat and so on including the applications that are based on Perfstat API or SPMI API varies to a certain extent at any point of time. If the command is run multiple times for an instance, the values may not be similar for that instance.