February 14, 2019 0 Comment

Nowadays, a high number of researchs have been conducted that focusing on the real-time systems. The real-time systems require a specific design deliberation due to the time constraints assigned to the task. The real-time systems are mainly immersed in our everyday life due to the quick progress of the embedded systems and mobiles and because of that; they do not only exist in the industry domains 2. To ensure that the behavior of the real-time system is correct, the execution of the tasks in hard real-time systems must be completed by their deadlines 1. The hierarchal off-line analysis framework used to guarantee the timing correctness of hard real-time systems 3. Furthermore, it is essential to the programmer and designer to know the time of execution of every task to indicate whether specific routines can achieve the requirement of the real-time application or not. Some hardware resources such as cache memory subsystem are not allowed for program execution time as they may lead to unpredictable variations in it. In most cases, the designer of the hard-real-time systems is forced to take the designing approach to worst-case specifications which is resulting in reducing the use of the processor. Subsequently, the hard-real-time systems are constraints to those circumstances where the worst-case performance is acceptable 3.
Caches are tiny and very fast memories that contain the modern referenced memory blocks 3. The caches effects on these blocks can be accessed by the CPU sooner based on the spatial and temporal locality of programmes. The average of execution time can be enhanced dramatically due to the utilization of caches. However; the execution assessment of a real-time system frequently relies upon its most worst-case execution time (WCET) and worst-case CPU use (WCU). Because of the dynamic behavior of the caches, the estimation of a system’s WCET and WCU will become more complex and imprecise. Timing analysis ought to be performed in both application project and real-time operating systems in order to get a convenient worst-case execution time for real systems. In other words, the interaction should be considered for these two parts 4. Many research has been conducted regarding the analysis of WCET to analyze the application programs using the analysis tools design. However; the majority of projects announced difficulties in analyzing real-time operating systems because many issues that may cause an extensive overestimation are uncovered 4. The cause of these problems is that small amount of information on the programs is taken by the analysis of RTOS. Furthermore, the conventional WCET analysis assumes not-interruptable projects. The assumption in a real-time system is invalidated because the existence of the real-time operating system introduces task preemption 4.
Based on the information above, it can be notice that the WCET which is designed for analyzing the application program does not handle the RTOS. In this paper, we will provide a survey of similar research topics on timing analysis of real-time systems based on the static methods. After that, the problems encountered are considered, and conceivable new difficulties are given as well as some of the challenges have also been identified in worst-case execution time analysis of applications 4.