Case Response Time Analysis Research Articles

Queue assignment for fixed-priority real-time flows in time-sensitive networks: Hardness and algorithm

Abstract Time sensitive networks (TSNs) enable deterministic real-time communication over Ethernet networks. According to IEEE 802.1Qbv standards, TSN switches use gates between queues and their corresponding egress ports to facilitate timing-deterministic communications. Management of switch resources, such as queues, has a significant impact on the schedulability of real-time flows. In this paper, we look into the theoretical foundation of queue management in TSN switches. We prove that the queue assignment problem for real-time flows on time sensitive networks under static priority scheduling is NP-hard in the strong sense, even if the number of queues per port is 3. Then we formulate the problem as a satisfiability modulo theories (SMT) specification. Besides, we propose a worst case response time analysis and a fast heuristic algorithms by eliminating scheduling conflicts. Experiments with randomly generated workload demonstrate the effectiveness of our algorithms for queue assignment of real-time flows.

WCRT Analysis and Evaluation for Sporadic Message-Processing Tasks in Multicore Automotive Gateways

We study the worst case response time (WCRT) analysis and evaluation for sporadic message-processing tasks in a multicore automotive gateway of a controller area network (CAN) cluster. We first build a multicore automotive gateway on CAN clusters. Two WCRT analysis methods for message-processing tasks in the multicore gateway are subsequently presented based on global and partitioned scheduling paradigms. We evaluate the WCRT results of two analysis methods with real message sets provided by the automaker, and present the design optimization guide.

Worst case response time and schedulability analysis for real-time software transactional memory-lazy conflict detection (STM-LCD)

Software transactional memory (STM) is a transactional mechanism of controlling access to shared resources in memory. This transactional mechanism is similar to the abort-and-restart execution model in a functional reactive system (FRS). Due to its abort-and-restart nature, the execution semantics of STM are different from the classic preemptive or nonpreemptive model. Some research has strong constraints for its worst case response time (WCRT) analysis. In this paper, we research on worst case response time and schedulability analysis for real-time software transactional memory-lazy conflict detection (STM-LCD). Specifically, we introduce a parameter the remainder factor m , formally derive an exact WCRT for a 2-task set on STM systems using lazy conflict detection (LCD), propose an exact schedulability test for a 2-task set. Also, we present a near-exact WCRT for an n -task set on STM-LCD, and propose a new necessary condition and a new sufficient condition to schedule an n -task set. Finally, we show that experimental results are accordant with the aforementioned analysis.

Worst Case Response Time Analysis of Sporadic Traffic in MVB

The Multifunction Vehicle Bus (MVB) protocol is well applied to train network control system where a set of process variables must be transferred between network devices. To cope with the real-time requirements of such system, the MVB protocol is designed to support both periodic and sporadic traffic. The periodic traffic is handled according to a static scheduling table, thus the schedulability can be certain after system initialization. However, for the sporadic traffic, the situation is different due to their irregular occurrence in the system. Therefore, more complex analysis must be made in order to guarantee its timing requirements. In this paper, a schedulability analysis is made by executing worst case response time analysis for sporadic traffic in MVB network.

A Technique to Calculate Cache Related Preemption Delay Using Constraints on Non-nested Preemptions

Abstract Caches incur an indirect cost to the response times of tasks due to preemptions in a task system. Hence the computation of Cache Related Preemption Delay (CRPD) is an important problem to assess the schedulability of a task system. In this paper, we have introduced the concept of inhibiting and non-nested preemptions. We have proposed a novel method to calculate tight upper and lower bounds on the number of preemptions of every task in the task-system across all phases . The problem of calculation of CRPD is modelled as a constraint satisfaction problem that can be solved by using Integer Linear Programming (ILP). The CRPD values are integrated in the worst case response time analysis.

An Efficient Test Method for Rate Monotonic Schedulability

Rate Monotonic scheduling algorithm has been widely used in real-time systems for its optimality in fixed priority scheduling. Determining the Rate Monotonic schedulability of tasks is an important problem when designing a real-time system. There are exact schedulability test methods for Rate Monotonic scheduling, but the worst case response time analysis on which the exact tests are based is NP-hard. So the exact tests are often too complex to be executed on-line for large numbers of tasks. For practical use, polynomial time sufficient conditions for the Rate Monotonic schedulability have been studied. However, existing polynomial time tests are often too pessimistic. In this paper, we propose a new polynomial time sufficient condition based on the response time analysis, which is less pessimistic than existing ones. Simulation results show that our test significantly outperforms the existing tests and has performance close to the exact test.

Modified Worst Case Response Time Analysis of CAN Bus Consisting of Nodes with Buffers

Worst case response time analysis of CAN Bus is the de facto method for evaluating the real-time performance which is a key feature of industrial bus. Compared with WCRT which aimed at nodes without buffer, a modified algorithm was presented to calculate the response time of CAN Bus consisting of nodes with both hardware and software buffers. The modified algorithm introduced local blocking time to describe the effect of buffers on response time. Based on the analysis of the different structures between hardware and software buffers, modified WCRT calculation methods of messages in hardware or software buffers were presented. Then the WCRT analysis of the whole system was obtained by consolidating the response time of node and bus. Results show that the response time calculated by the modified method is much longer than that calculated by the traditional WCRT. The modified method makes the WCRT analysis more coincident with the application of engineering, which helps the design and optimization of CAN based industrial bus.

Worst Case Response Time Analysis for Messages in Controller Area Network with Gateway

Worst Case Response Time Analysis for Messages in Controller Area Network with Gateway