Optimising task layout to increase schedulability via reduced cache related pre-emption delays
Proceedings of the 20th International Conference on Real-Time and Network Systems
Computation takes time, but how much?
Communications of the ACM
Approximation scheme for real-time tasks under fixed-priority scheduling with deferred preemption
Proceedings of the 21st International conference on Real-Time Networks and Systems
Explicit reservation of cache memory in a predictable, preemptive multitasking real-time system
ACM Transactions on Embedded Computing Systems (TECS)
A review of fixed priority and EDF scheduling for hard real-time uniprocessor systems
ACM SIGBED Review - Special Issue on the 3rd Embedded Operating System Workshop (EWiLi 2013)
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Without the use of caches the increasing gap between processor and memory speeds in modern embedded microprocessors would have resulted in memory access times becoming an unacceptable bottleneck. In such systems, cache related pre-emption delays can be a significant proportion of task execution times. To obtain tight bounds on the response times of tasks in pre-emptively scheduled systems, it is necessary to integrate worst-case execution time analysis and schedulability analysis via the use of an appropriate model of pre-emption costs.In this paper, we introduce a new method of bounding pre-emption costs, called the ECB-Union approach. The ECB-Union approach complements an existing UCB-Union approach. We improve upon both of these approaches via the introduction of Multiset variants which reduce the amount of pessimism in the analysis. Further, we combine these Multiset approaches into a simple composite approach that dominates both. These approaches to bounding pre-emption costs are integrated into response time analysis for fixed priority pre-emptively scheduled systems. Further, we extend this analysis to systems where tasks can access resources in mutual exclusion, in the process resolving omissions in existing models of pre-emption delays. A case study and empirical evaluation demonstrate the effectiveness of the ECB-Union, Multiset and combined approaches for a wide range of different cache configurations including cache utilization, cache set size, reuse, and block reload times.