scholarly journals Contention-Free Scheduling for Mixed-Criticality Multiprocessor Real-Time System

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1515
Author(s):  
Hyeongboo Baek ◽  
Kilho Lee
Keyword(s):  
Real Time ◽  
Schedulability Analysis ◽  
Multiprocessor Systems ◽  
Real Time Systems ◽  
Time System ◽  
Real Time System ◽  
Scheduling Policy ◽  
And Performance ◽  
Time Systems ◽  
Mixed Criticality

Zero-laxity (ZL) and contention-free (CF) policies have received considerable attention owing to their simplicity and applicability to real-time systems equipped with symmetry multiprocessors. Recently, the ZL policy for mixed-criticality (MC) systems has been proposed and studied, but the applicability to and performance of the CF policy for MC systems have not been investigated yet. In this paper, we propose the CF policy (as a scheduling policy) for MC symmetry multiprocessor systems, referred to as the MC systems tailored CF policy (MC-CF), and a schedulability analysis in support thereof. We define the notion of contention-free slots for two different criticalities (of MC systems) of tasks, propose a technique to limit the amount to be utilized for each task by defining an upper bound, and subsequently explain the way in which the contention-free slots are systematically utilized to improve the schedulability of MC symmetry multiprocessor systems. Following this, we develop a deadline analysis (DA) for MC-CF. Using our experimental results under various environmental settings, we demonstrate that MC-CF can significantly improve the schedulability of fixed-priority scheduling.

scholarly journals An Introduction to RTOS

2012 ◽  
pp. 285-289
Author(s):  
Sanjay Singh ◽  
Nishant Tripathi ◽  
Anil Kumar Chaudhary ◽  
Mahesh Kumar Singh
Keyword(s):  
Operating System ◽  
Real Time ◽  
Level Of Service ◽  
Real Time Systems ◽  
Time System ◽  
Real Time System ◽  
Real Time Operating System ◽  
System A ◽  
External Stimuli ◽  
Time Systems

RTOS (real time operating system) can be defined as “The ability of the operating system to provide a required level of service in bounded response time.” A real time system responds in a (timely) predictable way to unpredictable external stimuli arrivals. To build a predictable system, all its components (hardware & software) should enable this requirement to be fulfilled. Traffic on a bus for example should take place in a way allowing all events to be managed within the prescribe time limit. However it should not be forgotten that a good RTOS is only is building block. Using it in a wrongly designed system may lead to a malfunctioning of the RT system. A good RTOS can be defined as one that has a bounded (predictable) behavior under all system load scenarios (simultaneous interrupts and thread execution). In RT system, each individual deadline should be met. Real-time systems are designed to control and monitor their environment. Most of these systems are using sensors to collect environment state and use actuators to change something.

scholarly journals Schedulability Analysis Towards Arbitrarily Activated Tasks in Mixed-Criticality Systems

2017 ◽  
Vol 26 (10) ◽  
pp. 1750159 ◽  
Author(s):  
Biao Hu ◽  
Kai Huang ◽  
Gang Chen ◽  
Long Cheng ◽  
Dongkun Han ◽  
...  
Keyword(s):  
Real Time ◽  
Schedulability Analysis ◽  
Real Time Systems ◽  
Activation Patterns ◽  
Task Model ◽  
Efficient Resource ◽  
Task Priority ◽  
Time Systems ◽  
Sufficient Test ◽  
Mixed Criticality

The integration of mixed-critical tasks into a platform is an increasingly important trend in the design of real-time systems due to its efficient resource usage. With a growing variety of activation patterns considered in real-time systems, some of them capture arbitrary activation patterns. As a consequence, the existing scheduling approaches in mixed-criticality systems (MCs), which assume the sporadic tasks with implicit deadlines, have sometimes become inapplicable or are ineffective. In this paper, we extend the sporadically activated task model to the arbitrarily activated task model in MCs with the preemptive fixed-task-priority schedule. By using the event arrival curve to model task activations, we present the necessary and sufficient schedulability tests that are based on the well-established results from Real-Time Calculus. We propose to use the busy-window analysis to do the sufficient test because it has been shown to be tighter than the sufficient test of using Real-Time Calculus. According to our experimental results, for sporadic task sets, our proposed test can achieve the same performance as the state-of-the-art schedulability test. However, compared with the previous schedulability analysis of preemptive fixed-task-priority, our approaches can handle more general tasks with blocking, jitter, and arbitrary deadlines.

scholarly journals Reducing Dynamic Power Consumption in Mixed-Critical Real-Time Systems

2020 ◽  
Vol 10 (20) ◽  
pp. 7256
Author(s):  
Ijaz Ali ◽  
Yong-Il Jo ◽  
Seonah Lee ◽  
Wan Yeon Lee ◽  
Kyong Hoon Kim
Keyword(s):  
Real Time ◽  
Energy Minimization ◽  
Real Time Systems ◽  
Real Time System ◽  
Dynamic Power ◽  
Frequency Level ◽  
Memory Power ◽  
System Frequency ◽  
Time Systems ◽  
Mixed Criticality

In this paper, we study energy minimization consumption of a mixed criticality real-time system on uni-core. Our focus is on a new scheduling scheme to decrease the frequency level in order to conserve power. Since many systems are equipped with dynamic power and frequency level memory, power can be saved by decreasing the system frequency. In this paper, we provide new dynamic energy minimization consumption in mixed-criticality real-time systems. Recent research has been done on low-criticality mode for power reduction. Thus, the proposed scheme can reduce the energy both in high-criticality and low-criticality modes. The effectiveness of our proposed scheme in energy reduction is clearly shown through simulations results.

ADDING FORM TO REAL-TIME SYSTEM SPECIFICATION AND SIMULATION

1999 ◽  
Vol 09 (05) ◽  
pp. 643-661 ◽  
Author(s):  
JI Y. LEE ◽  
KYO C. KANG ◽  
GERARD J. KIM ◽  
HYE J. KIM
Keyword(s):  
Real Time ◽  
Critical Role ◽  
Real Time Systems ◽  
System Specification ◽  
Time System ◽  
Real Time System ◽  
Interactive Behavior ◽  
Behavior Function ◽  
And Behavior ◽  
Time Systems

Specification and validation of a real-time system are often based on making simplistic predictions and assumptions about relevant behavior of the external environment and the controlled device interacting with it. However, in many cases, real-time systems physically interact with other external objects in a complex manner in a dynamically changing world and thus, their form (e.g. physical properties such as shape, mass, material, and configuration) can play a critical role in producing a correct specification and obtaining realistic simulation output. We present ASADAL/PROTO, a specification and simulation tool for real-time systems, that takes form into account in addition to the function and behavior handled by ASADAL/SIM, its predecessor. Simulation of the control system specification runs in conjunction with the environmental simulation, and the resulting interactive behavior of the controlled system is observed visually for analysis. Our vision is to incrementally model, simulate and analyze all three views (behavior, function, and form) of real-time system specification for its increased level of confidence at early prototyping stage.

Synchronization-Aware Task Allocation Techniques for Preemption Control to Reduce Blocking Time in Multiprocessor Real-Time System

2020 ◽  
Vol 11 (4) ◽  
pp. 60-79
Author(s):  
Ajitesh Kumar ◽  
Sanjai Kumar Gupta
Keyword(s):  
Real Time ◽  
Task Completion ◽  
Real Time Systems ◽  
Time System ◽  
Real Time System ◽  
Priority Inversion ◽  
Context Switching ◽  
Optimal Approach ◽  
Result Analysis ◽  
Time Systems

Multiprocessor real-time systems receive a great deal of attention. For better utilization of multiprocessors in a real-time context, an optimal approach for scheduling, allocation, and synchronization is required. In this research, a novel heuristic synchronization-aware scheduling has been proposed to reduce the blocking delays in a critical section and also bound to minimize multiple priority inversion. The key idea of this technique is to assign the task set in the same processor that accesses a common shared resource and also access them for the longest period of time; thereby, the global sharing of resource transforms into local sharing. From simulation results, it was concluded that the duration of blocking overheads should be minimized up to 25% to 30% and context switching between processors also reduced up to 10% to 15%. On the basis of result analysis, schedulability, minimization of context switching, and reduced blocking time indicate that the proposed method outperforms the existing methods and does not affect the task completion time.

scholarly journals Scheduling Algorithms Implementation for Real Time Operating Systems: A Review

2021 ◽  
pp. 35-51
Author(s):  
Gulistan Ahmead Ismael ◽  
Azar Abid Salih ◽  
Adel AL-Zebari ◽  
Naaman Omar ◽  
Karwan Jameel Merceedi ◽  
...  
Keyword(s):  
Real Time ◽  
Nuclear Reactor ◽  
Time Frame ◽  
Real Time Systems ◽  
Time System ◽  
Real Time System ◽  
Safety Control ◽  
Time Component ◽  
Paper Review ◽  
Time Systems

The term "Real-Time Operating System (RTOS)" refers to systems wherein the time component is critical. For example, one or more of a computer's peripheral devices send a signal, and the computer must respond appropriately within a specified period of time. Examples include: the monitoring system in a hospital care unit, the autopilot in the aircraft, and the safety control system in the nuclear reactor. Scheduling is a method that ensures that jobs are performed at certain times. In the real-time systems, accuracy does not only rely on the outcomes of calculation, and also on the time it takes to provide the results. It must be completed within the specified time frame. The scheduling strategy is crucial in any real-time system, which is required to prevent overlapping execution in the system. The paper review classifies several previews works on many characteristics. Also, strategies utilized for scheduling in real time are examined and their features compared.

Formal Specification of a Wall-Climbing Robot Using Z – A Case Study of Small-Scale Embedded Hard Real-Time System

2012 ◽  
Author(s):  
Radziah Mohamad ◽  
Dyg. Norhayati Abg. Jawawi ◽  
Safaai Deris ◽  
Rosbi Mamat
Keyword(s):  
Real Time ◽  
Formal Methods ◽  
Software Reliability ◽  
Formal Specification ◽  
Small Scale ◽  
Real Time Systems ◽  
Time System ◽  
Real Time System ◽  
Hard Real Time ◽  
Time Systems

Aktiviti menguji sama ada sistem masa nyata memenuhi spesifikasi masa dan keserempakan adalah sangat penting. Salah satu bidang penyelidikan dalam bidang keboleh-percayaan perisian ialah teknik formal yang cuba untuk membuktikan kesahihan sesuatu atur cara dengan spesifikasinya. Oleh kerana masa dan keserampakan merupakan aspek yang penting dalam sistem masa nyata, keperluan untuk menggunakan teknik formal sebagai teknik untuk mengesahkan aspek masa dan keserempakan ini adalah amat tinggi. Kertas kerja ini mengkaji proses membina spesifikasi formal untuk sistem masa nyata berskala kecil dengan menggunakan teknik Z. Spesifikasi formal yang dibangunkan di dalam kertas kerja ini diharap dapat membantu proses penganalisisan fasa reka bentuk di awal proses pembangunan sistem. Kertas kerja ini juga diharap dapat menjadi rujukan kepada projek–projek teknik formal yang akan datang terutamanya projek yang berkaitan dengan sistem masa nyata berskala kecil. Kata kunci: Kebolehpercayaan perisian; spesifikasi formal; Z; masa nyata; sistem berskala kecil. The task of checking whether a real–time system satisfies its timing and concurrency specifications is extremely important. One major area of research addressing software reliability aspect is called formal method, which attempts to prove the correctness of programs with respect to system specifications. Since, timing and concurrency properties can very important in the operation of real–time systems, there is a need for applying formal methods to verify timing properties. This paper investigates the process of building a formal specification of a small-scale embedded hard real–time systems using Z. It is expected that the formal specification presented in this paper can provide assistance in analysing design trade–offs early in the development process. It is also expected that this paper can act as the foundation for any upcoming formal methods related project especially for small-scale real–time systems project. Key words: Software reliability; formal specification; Z; hard real-time; small-scale systems

The Research on Embedded Real-Time System Security Issues in Mechanical Control

2013 ◽  
Vol 681 ◽  
pp. 65-71
Author(s):  
Xu Hui Wang
Keyword(s):  
Programming Languages ◽  
Real Time ◽  
System Reliability ◽  
System Security ◽  
Malicious Code ◽  
Real Time Systems ◽  
Time System ◽  
Real Time System ◽  
Security Issues ◽  
Time Systems

Embedded real-time systems are facing more and more security problems. Malicious attacks on the system from suspicious or malicious code and the change of system hardware state could lead to system exception, resulting in system reliability and security deteriorated. This paper summarizes the characteristics of embedded real-time system and its special requirements for security, analyses security problems faced by embedded real-time system and defects of programming languages. And then put forward methods to improve the safety of embedded real-time system, providing a new security the idea for solving the embedded real-time system security.

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