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Evaluation of Static Time Analysis for CC Systems

Fulltext:


Authors:

Ola Eriksson

Publication Type:

Report - MRTC

ISRN:

MDH-MRTC-183/2005-1-SE


Abstract

Most processors today are embedded in products like mobile phones, microwave owens, welding machines etc and are not used in PC’s as many believe. Since some of these embedded computers are used in time-critical or safety-critical systems it is very important that the behaviour of these systems are well known. One part of that is to know the Worst Case Execution Time (WCET) of the different tasks in the embedded system. The traditional method of finding the WCET of a task is by measuring the execution time of the task when it is running on the target system. There are several problems with this approach. It is hard to check that the time you have got is actually the WCET. Today there is another possibility to find the WCET. You can use static timing analysis that does not execute the program in order to find the WCET; instead it uses a model of the target hardware and uses static methods to calculate the WCET. There are a few commercial static WCET tools on the market and a few more academic ones, but so far no industry has started to use these on a regular basis. This work was done at CC-Systems (CCS) in Västerås. CCS develops and delivers electronic solutions and software for machines and vehicles in tough environments. This means that some of their code is time-critical. The purpose of this thesis work was to find out if it is possible to integrate the static WCET tool in CCS development tool chain and also to see if CCS would benefit from it. If it was possible to do so they also wanted to know if they must change their development process or make other changes to make it easier to analyse their code by a static tool. CCS was also interested to know if the static tool could be of use in other areas than WCET analysis, for example giving their simulation technique a correct timing behaviour. To be able to compare the results of the static WCET analysis considering effort and accuracy, dynamic WCET analysis was also performed on the same code snippets as with the static tool. The dynamic measurements was a part of another thesis on CCS performed by Yina Zhang. The purpose of her thesis was to evaluate different dynamic WCET analysis methods and to see if any of the methods is well suited for CCS. She also evaluated what CCS could do to make it easier to analyse their code with the selected WCET analysis method and if they could use the WCET analysis methods for other things than just WCET analysis. One part of her thesis was also to evaluate the currently used methods of finding WCET values on CCS. The overall conclusion of this thesis is that to be able to get both tight and safe WCET values static methods should preferably be used. Dynamic methods can however help the static method giving tighter WCET values since they can be used to give input to the static analysis, for example give information about memory accesses. If general timing behaviour of the system is wanted dynamic methods are prefered since today’s static methods can’t provide this kind of information.

Bibtex

@techreport{Eriksson821,
author = {Ola Eriksson},
title = {Evaluation of Static Time Analysis for CC Systems},
number = {ISSN 1404-3041 ISRN MDH-MRTC-183/2005-1-SE},
month = {August},
year = {2005},
url = {http://www.es.mdu.se/publications/821-}
}