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Theories for Estimating Execution Times in Soft Real-Time Systems Applied in the Telecommunication Domain



Johan Erikson , Jouni Axelsson

Publication Type:



MRTC and IDt, Mälardalen University


Real-time systems are normally divided into two classes: Hard and Soft. The difference lies in how critical it is to meet the systems timing constraints. In a hard real-time system, every deadline must be met. If not, the conse- quences to the environment is above an accepted level. On account of this, the Worst Case Execution Time is in focus for a number of proposed ap- proaches. A soft real-time system, on the other hand, is characterized by the fact that a missed deadline do not cause system failure and do not cause damage to the environment. This is most likaly the reason why timing constraints in soft real-time systems are handled by diÿerent ad hoc solutions. (E.g. Do not write more than k lines of code in one block.) But even if a missed deadline is not directly dangerous, the consequences may indirectly be serious. In this report, we propose a more systematic approach to handle execution times in soft real-time systems. A combination of graphical representation of the system together with information on loops, gives the developers a pic- ture of the execution time which enable identi½cation of critical areas and parts that use much time relative other parts of the system. The graphical representation is annotated with estimated execution times. Loop detection is based on DJ graphs and processes the control ²ow graph of the program which, in our case, is extracted from the back end of the compiler. The theories is applied in the telecommunication domain where the targeted system (the AXE telecommunication system from Ericsson) has about 10 milion lines of code spread over about 1000 executable units, continously developed during 25 years.


author = {Johan Erikson and Jouni Axelsson},
title = {Theories for Estimating Execution Times in Soft Real-Time Systems Applied in the Telecommunication Domain},
month = {October},
year = {2001},
publisher = {MRTC and IDt, M{\"a}lardalen University},
url = {}