TASKING VX-toolset for ARM User Guide

Chapter 6. ProfilingProfiling is the process of collecting statistical data about a running application. With these data you cananalyze which functions are called, how often they are called and what their execution time is.This chapterdescribes the TASKING profiling method with code instrumentation techniques and static profiling.6.1. What is Profiling?Profiling is a collection of methods to gather data about your application which helps you to identify codefragments where execution consumes the greatest amount of time.TASKING supplies a number of profiler tools each dedicated to solve a particular type of performancetuning problem. Performance problems can be solved by:• Identifying time-consuming algorithms and rewrite the code using a more time-efficient algorithm.• Identifying time-consuming functions and select the appropriate compiler optimizations for these functions(for example, enable loop unrolling or function inlining).• Identifying time consuming loops and add the appropriate pragmas to enable the compiler to furtheroptimize these loops.A profiler helps you to find and identify the time consuming constructs and provides you this way withvaluable information to optimize your application.TASKING employs various schemes for collecting profiling data, depending on the capabilities of thetarget system and different information needs.6.1.1. Methods of ProfilingThere are several methods of profiling: recording by an instruction set simulator, profiling with codeinstrumentation techniques (dynamic profiling) and profiling by the C compiler at compile time (staticprofiling). Each method has its advantages and disadvantages.Profiling by an instruction set simulatorOne way to gather profiling information is built into the instruction set simulator (ISS). The ISS recordsthe time consumed by each instruction that is executed. The debugger then retrieves this information andcorrelates the time spent for individual instructions to C source statements.Advantages• it gives (cycle) accurate information with extreme fine granularity• the executed code is identical to the non-profiled codeDisadvantages• the method requires an ISS as execution environment177