Scheduling Techniques for Operating Systems for Medical and IoT Devices: A Review

Software and Hardware synthesis are the major subtasks in the implementation of hardware/software systems. Increasing trend is to build SoCs/NoC/Embedded System for Implantable Medical Devices (IMD) and Internet of Things (IoT) devices, which includes multiple Microprocessors and Signal Processors, allowing designing complex hardware and software systems, yet flexible with respect to the delivered performance and executed application. An important technique, which affect the macroscopic system implementation characteristics is the scheduling of hardware operations, program instructions and software processes. This paper presents a survey of the various scheduling strategies in process scheduling. Process Scheduling has to take into account the real-time constraints. Processes are characterized by their timing constraints, periodicity, precedence and data dependency, pre-emptivity, priority etc. The affect of these characteristics on scheduling decisions has been described in this paper

Performance Analysis of Preemptive Based Uniprocessor Scheduling

All the real-time systems are bound with response time constraints, or else, there is a risk of  severe consequences, which includes failure. The System will fail when not able to meet the requirements according to the specifications. The problem of real-time scheduling is very vast, ranging from uni-processor to complicated-multiprocessor. In this paper, we have compared the performance of real-time tasks that should be scheduled properly, to get optimum performance. Analysis methodology and the concept of optimization leads to the design of appropriate scheduling. We have done  the analysis among RM and EDF algorithm that are important for scheduling in uni-processor

A Survey of Fault-Tolerance Techniques for Embedded Systems from the Perspective of Power, Energy, and Thermal Issues

The relentless technology scaling has provided a significant increase in processor performance, but on the other hand, it has led to adverse impacts on system reliability. In particular, technology scaling increases the processor susceptibility to radiation-induced transient faults. Moreover, technology scaling with the discontinuation of Dennard scaling increases the power densities, thereby temperatures, on the chip. High temperature, in turn, accelerates transistor aging mechanisms, which may ultimately lead to permanent faults on the chip. To assure a reliable system operation, despite these potential reliability concerns, fault-tolerance techniques have emerged. Specifically, fault-tolerance techniques employ some kind of redundancies to satisfy specific reliability requirements. However, the integration of fault-tolerance techniques into real-time embedded systems complicates preserving timing constraints. As a remedy, many task mapping/scheduling policies have been proposed to consider the integration of fault-tolerance techniques and enforce both timing and reliability guarantees for real-time embedded systems. More advanced techniques aim additionally at minimizing power and energy while at the same time satisfying timing and reliability constraints. Recently, some scheduling techniques have started to tackle a new challenge, which is the temperature increase induced by employing fault-tolerance techniques. These emerging techniques aim at satisfying temperature constraints besides timing and reliability constraints. This paper provides an in-depth survey of the emerging research efforts that exploit fault-tolerance techniques while considering timing, power/energy, and temperature from the real-time embedded systems’ design perspective. In particular, the task mapping/scheduling policies for fault-tolerance real-time embedded systems are reviewed and classified according to their considered goals and constraints. Moreover, the employed fault-tolerance techniques, application models, and hardware models are considered as additional dimensions of the presented classification. Lastly, this survey gives deep insights into the main achievements and shortcomings of the existing approaches and highlights the most promising ones

Scheduling real-time, periodic jobs using imprecise results

A process is called a monotone process if the accuracy of its intermediate results is non-decreasing as more time is spent to obtain the result. The result produced by a monotone process upon its normal termination is the desired result; the error in this result is zero. External events such as timeouts or crashes may cause the process to terminate prematurely. If the intermediate result produced by the process upon its premature termination is saved and made available, the application may still find the result unusable and, hence, acceptable; such a result is said to be an imprecise one. The error in an imprecise result is nonzero. The problem of scheduling periodic jobs to meet deadlines on a system that provides the necessary programming language primitives and run-time support for processes to return imprecise results is discussed. This problem differs from the traditional scheduling problems since the scheduler may choose to terminate a task before it is completed, causing it to produce an acceptable but imprecise result. Consequently, the amounts of processor time assigned to tasks in a valid schedule can be less than the amounts of time required to complete the tasks. A meaningful formulation of this problem taking into account the quality of the overall result is discussed. Three algorithms for scheduling jobs for which the effects of errors in results produced in different periods are not cumulative are described, and their relative merits are evaluated

Energy-Efficient Fault-Tolerant Scheduling Algorithm for Real-Time Tasks in Cloud-Based 5G Networks

© 2013 IEEE. Green computing has become a hot issue for both academia and industry. The fifth-generation (5G) mobile networks put forward a high request for energy efficiency and low latency. The cloud radio access network provides efficient resource use, high performance, and high availability for 5G systems. However, hardware and software faults of cloud systems may lead to failure in providing real-time services. Developing fault tolerance technique can efficiently enhance the reliability and availability of real-time cloud services. The core idea of fault-tolerant scheduling algorithm is introducing redundancy to ensure that the tasks can be finished in the case of permanent or transient system failure. Nevertheless, the redundancy incurs extra overhead for cloud systems, which results in considerable energy consumption. In this paper, we focus on the problem of how to reduce the energy consumption when providing fault tolerance. We first propose a novel primary-backup-based fault-tolerant scheduling architecture for real-time tasks in the cloud environment. Based on the architecture, we present an energy-efficient fault-tolerant scheduling algorithm for real-time tasks (EFTR). EFTR adopts a proactive strategy to increase the system processing capacity and employs a rearrangement mechanism to improve the resource utilization. Simulation experiments are conducted on the CloudSim platform to evaluate the feasibility and effectiveness of EFTR. Compared with the existing fault-tolerant scheduling algorithms, EFTR shows excellent performance in energy conservation and task schedulability

Scheduling periodic jobs using imprecise results

One approach to avoid timing faults in hard, real-time systems is to make available intermediate, imprecise results produced by real-time processes. When a result of the desired quality cannot be produced in time, an imprecise result of acceptable quality produced before the deadline can be used. The problem of scheduling periodic jobs to meet deadlines on a system that provides the necessary programming language primitives and run-time support for processes to return imprecise results is discussed. Since the scheduler may choose to terminate a task before it is completed, causing it to produce an acceptable but imprecise result, the amount of processor time assigned to any task in a valid schedule can be less than the amount of time required to complete the task. A meaningful formulation of the scheduling problem must take into account the overall quality of the results. Depending on the different types of undesirable effects caused by errors, jobs are classified as type N or type C. For type N jobs, the effects of errors in results produced in different periods are not cumulative. A reasonable performance measure is the average error over all jobs. Three heuristic algorithms that lead to feasible schedules with small average errors are described. For type C jobs, the undesirable effects of errors produced in different periods are cumulative. Schedulability criteria of type C jobs are discussed

Problems related to the integration of fault tolerant aircraft electronic systems

Problems related to the design of the hardware for an integrated aircraft electronic system are considered. Taxonomies of concurrent systems are reviewed and a new taxonomy is proposed. An informal methodology intended to identify feasible regions of the taxonomic design space is described. Specific tools are recommended for use in the methodology. Based on the methodology, a preliminary strawman integrated fault tolerant aircraft electronic system is proposed. Next, problems related to the programming and control of inegrated aircraft electronic systems are discussed. Issues of system resource management, including the scheduling and allocation of real time periodic tasks in a multiprocessor environment, are treated in detail. The role of software design in integrated fault tolerant aircraft electronic systems is discussed. Conclusions and recommendations for further work are included

최신 ECU보드를 활용하여 소프트에러들을 실시간 복구하는 기법

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 컴퓨터공학부, 2020. 8. 이창건.This dissertation presents the fault-tolerant real-time scheduling using dynamic mode switch support of modern ECU hardware. This dissertation first describes the optimal capacity of the Periodic Resource which contains harmonic periodic task set using the exact time supply function.We show that the optimal capacity can be represented as sum of the each individual utilization of the task in the harmonic periodic task set for both normal state(i.e. no faults) and faulty state. Then, this dissertation proposes non-critical task overlapping technique by only using the idle time intervals of the Periodic Resource in order to overlap the non-critical tasks which ensures no additional capacity increase. Finally, this dissertation proposes the basic form of the Periodic Resources in order to efficiently use the dynamic mode switch support. Next, we also proposes the bin-packing heuristic algorithm that considers both making sub-taskset as a one Periodic Resource and Periodic Resource wide bin-packing which has the pseudo-polynomial time complexity. Experimental results show that the proposed algorithm performs better than the traditional partitioned fixed-priority scheduling approach and partitioned mixed-criticality scheduling approach. Also, the achievement is made up to 18% in terms of the total needed cores compared to traditional partitioned fixed-priority approach for making the given input task set schedulable.본 논문에서는 효율적인 재구성가능 시스템 사용을 위한 계층기반 실시간 결함 감내 스케줄링 기법을 제안한다. 본 연구는 주기 자원 모델을 기반으로, 최적 주기 자원 서버의 용량을 주기 자원 모델이 가지는 실시간 주기 태스크 셋의 유틸라이제이션의 합으로 제시한다. 본 논문은 해당 최적 서버 용량을 시스템이 정상 동작할때와 오동작 할때 모두에 대해서 제시한다. 다음으로, 비중요 태스크 셋들을 중요 주기 자원 서버의 여분 공백 시간을 활용해 서버 용량의 증가 없이 비중요 태스크를 중요 주기 자원 서버에 할당하는 방법론을 제시한다. 마지막으로 본 논문은 주기 자원 서버 단위의 파티션 기법과 주기 태스크를 하나의 주기 자원 서버로 만드는 빈패킹 휴리스틱 알고리즘을 제시한다. 실험 결과, 본 논문에서 제시한 알고리즘은 기존에 사용되었던 파티션 기반 우선순위 스케줄링 알고리즘과 파티션 기반 우선순위 혼잡 중요도 알고리즘보다 더 작은 수의 코어의 개수를 도출 할 수 있음을 보인다. 실험결과를 기반으로, 본 연구에서 제안한 알고리즘을 재구성가능 시스템에 활용한다면 기존 방법 대비 최대 18%의 코어절감효과를 기대할수 있다.1 Introduction 1 1.1 Motivation and Objective 1 1.2 Approach 2 1.3 Organization 6 2 System Model 7 3 Schedulability Analysis 10 3.1 Background 10 3.2 Optimal Capacity Analysis During Normal State 14 3.3 Optimal Capacity Analysis During Fault State 16 3.4 Periodic Resource Wide Schedulability Test 20 3.5 Non-Critical Task Overlapping 24 4 Proposed Approach 26 4.1 Minimum Harmonic Partitions of the Task Set 26 4.2 Proposed Heuristic Algorithm 28 4.2.1 Choosing Detection method 28 4.2.2 Packing Minimum Harmonic Partitions 29 4.2.3 Packing Free Tasks 30 4.2.4 Packing Non-Critical Tasks 31 4.3 Algorithm Description 32 5 Evaluation 35 5.1 Experimental Setup 35 5.2 Simulation Results 36 5.2.1 Free Task Bin-Packing 38 5.2.2 Minimum Harmonic Partitions Bin-Packing 40 5.2.3 Effect of Non-Critical Task Overlapping 43 5.2.4 Effect of State-Wise Computation 45 6 Related Works 46 6.1 Hierarchical Fault-Tolerant Real-Time Scheduling 46 6.2 Error Detection Method 46 7 Conclusion 48 References 50Maste

Quantifying the Resiliency of Fail-Operational Real-Time Networked Control Systems

In time-sensitive, safety-critical systems that must be fail-operational, active replication is commonly used to mitigate transient faults that arise due to electromagnetic interference (EMI). However, designing an effective and well-performing active replication scheme is challenging since replication conflicts with the size, weight, power, and cost constraints of embedded applications. To enable a systematic and rigorous exploration of the resulting tradeoffs, we present an analysis to quantify the resiliency of fail-operational networked control systems against EMI-induced memory corruption, host crashes, and retransmission delays. Since control systems are typically robust to a few failed iterations, e.g., one missed actuation does not crash an inverted pendulum, traditional solutions based on hard real-time assumptions are often too pessimistic. Our analysis reduces this pessimism by modeling a control system\u27s inherent robustness as an (m,k)-firm specification. A case study with an active suspension workload indicates that the analytical bounds closely predict the failure rate estimates obtained through simulation, thereby enabling a meaningful design-space exploration, and also demonstrates the utility of the analysis in identifying non-trivial and non-obvious reliability tradeoffs