Introduction to Performance Profiling

The ChorusOS operating system performance profiling system contains a set of tools that facilitate the analysis and optimization of the performance of the ChorusOS operating system and applications. These tools relate only to system components sharing the system address space, that is, the ChorusOS operating system components and supervisor application processes. This set of tools is composed of a profiling server, libraries for building profiled processes, a target controller, and a host utility.

Software performance profiling consists of collecting data about the dynamic behavior of the software to identify the time distribution. For example, the performance profiling system is able to report the time spent within each procedure, as well as providing a dynamically constructed call graph.

Typical steps in a ChorusOS optimization are:

1. Bench a set of typical applications, using the ChorusOS operating system and applications at peak performance. The selection of these applications is essential because the system will eventually be tuned for this specific type of application.

2. Evaluate and record the output of the benchmarks.

3. To use the performance profiling system to collect raw data about the dynamic behavior of the applications.

4. Generate, evaluate, and record the performance profiling reports.

5. Plan and implement optimizations, for example, rewriting certain time-critical routines in assembly language, using in-line functions, or tuning algorithms.

The performance profiling tools provide two different classes of service, depending on the method used to prepare the software being measured:

• The performance profiling system is applied to software generated in the standard way, (the same version as used for benchmarking). In this case, the performance profiling reports only minimal information, which consists mainly of the percentage of time spent in each routine of the software. The corresponding performance profiling report is called simple form.

• The performance profiling system is applied to software regenerated exclusively for performance profiling; software is completely recompiled, using the performance profiling C compiler option (usually the -p option). This enables the performance profiling system to report more information by dynamically counting routine invocations and building a complete call graph. The corresponding performance profiling report is called full form.

The standard (binary) version of the ChorusOS operating system is not compiled with the performance profiling option. Profiling a system will only generate a simple form. Non-profiled components (or components for which a simple report form is sufficient) need not be compiled with the performance profiling option.

To obtain a full form for ChorusOS operating system components, a source product distribution is needed. In this case, it is necessary to regenerate the system components with the performance profiling option set.