scholarly journals Using Trace Scratchpads to Reduce Execution Times in Predictable Real-Time Architectures

2008 ◽  
Author(s):  
Jack Whitham ◽  
Neil Audsley
Keyword(s):  
Real Time ◽  
Execution Times

scholarly journals Optimisation of scheduled tasks by real-time measurement and correlation

2020 ◽  
pp. 36-43
Author(s):  
Berkay Saydam ◽  
Cem Orhan ◽  
Niyazi Toker ◽  
Mansur Turasan
Keyword(s):  
Real Time ◽  
Functional Safety ◽  
Worst Case ◽  
System Cost ◽  
Simulation Tools ◽  
Real Time Measurement ◽  
Real Hardware ◽  
Execution Times ◽  
Time Critical ◽  
Time Systems

For functional safety, the scheduler should perform all time critical tasks in an order and within predefined deadlines in embedded systems. Scheduling of time critical tasks is determined by estimating their worst-case execution times. To justify the model design of task scheduling, it is required to simulate and visualise the task execution and scheduling maps. This helps to figure out possible problems before deploying the schedule model to real hardware. The simulation tools which are used by companies in an industry perform scheduling simulation and visualisation of all time critical tasks to design and verify the model. All of them lack the capability of comparing simulation results versus real results to achieve the optimised scheduling design. This sometimes leads the overestimated worst-case execution times and increased system cost. The aim of our study is to decrease the system cost with optimisation of scheduled tasks via using the static analysing method.   Keywords: Schedule visualisation, scheduler optimisation, functional safety, real-time systems, scheduler.

scholarly journals Rigorous implementation of real-time systems – from theory to application

2013 ◽  
Vol 23 (4) ◽  
pp. 882-914 ◽  
Author(s):  
TESNIM ABDELLATIF ◽  
JACQUES COMBAZ ◽  
JOSEPH SIFAKIS
Keyword(s):  
Real Time ◽  
Physical Model ◽  
Timing Constraints ◽  
Abstract Model ◽  
Real Time Systems ◽  
Execution Engine ◽  
Execution Platform ◽  
Implementation Method ◽  
Execution Times ◽  
Time Systems

The correct and efficient implementation of general real-time applications remains very much an open problem. A key issue is meeting timing constraints whose satisfaction depends on features of the execution platform, in particular its speed. Existing rigorous implementation techniques are applicable to specific classes of systems, for example, with periodic tasks or time-deterministic systems.We present a general model-based implementation method for real-time systems based on the use of two models: •An abstract model representing the behaviour of real-time software as a timed automaton, which describes user-defined platform-independent timing constraints. Its transitions are timeless and correspond to the execution of statements of the real-time software.•A physical model representing the behaviour of the real-time software running on a given platform. It is obtained by assigning execution times to the transitions of the abstract model. A necessary condition for implementability is time-safety, that is, any (timed) execution sequence of the physical model is also an execution sequence of the abstract model. Time-safety simply means that the platform is fast enough to meet the timing requirements. As execution times of actions are not known exactly, time-safety is checked for the worst-case execution times of actions by making an assumption of time-robustness: time-safety is preserved when the speed of the execution platform increases.We show that, as a rule, physical models are not time-robust, and that time-determinism is a sufficient condition for time-robustness. For a given piece of real-time software and an execution platform corresponding to a time-robust model, we define an execution engine that coordinates the execution of the application software so that it meets its timing constraints. Furthermore, in the case of non-robustness, the execution engine can detect violations of time-safety and stop execution.We have implemented the execution engine for BIP programs with real-time constraints and validated the implementation method for two case studies. The experimental results for a module of a robotic application show that the CPU utilisation and the size of the model are reduced compared with existing implementations. The experimental results for an adaptive video encoder also show that a lack of time-robustness may seriously degrade the performance for increasing platform execution speed.

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