Measuring and Analysing Execution Time in an Automotive Real-Time Application

Abstract: Autoliv has developed the Night Vision system, which is a safety system for use incars to improve the driver’s situational awareness during night conditions. It is areal-time system that is able to detect pedestrians in the traffic environment andissue warnings when there is a risk of collision. The timing behaviour of programsrunning on real-time systems is vital information when developing and optimisingboth hardware and software. As a part of further developing their Night Visionsystem, Autoliv wanted to examine detailed timing behaviour of a specific part ofthe Night Vision algorithm, namely the Tracking module, which tracks detectedpedestrians. Parallel to this, they also wanted a reliable method to obtain timingdata that would work for other parts of that system as well, or even other applications. A preliminary study was conducted in order to determine the most suitable methodof obtaining the timing data desired. This resulted in a measurement-based approachusing software profiling, in which the Tracking module was measured usingvarious input data. The measurements were performed on simulated hardwareusing both a cycle accurate simulator and measurement tools from the systemCPU manufacturer, as well as tools implemented specifically to handle input andoutput data. The measurements resulted in large amounts of data used to compile performancestatistics. Using different scenarios in the input data, we were able to obtain timingcharacteristics for several typical situations the system may encounter duringoperation. By manipulating the input data we were also able to observe generalbehaviour and achieve artificially high execution times, which serves as indicationson how the system responds to irregular and unexpected input data. The method used for collecting timing information was well suited for this particularproject. It provided the possibility to analyse behavior in a better waythan other, more theoretical, approaches would have. The method is also easilyadaptable to other parts of the Night Vision system, or other systems, with onlyminor adjustments to measurement environment and tools.