| 1. |
- Aminifar, Amir, et al.
(författare)
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Jfair: A Scheduling Algorithm to Stabilize Control Applications
- 2015
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Ingår i: <em>21st IEEE Real-Time and Embedded Technology and Applications Symposium, Cyber-Physical Systems Week, Seattle, WA, April 2015</em>. - : IEEE Computer Society. - 9781479986033 ; , s. 63-72
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Konferensbidrag (refereegranskat)abstract
- Control applications are considered to be among the core applications in cyber-physical and embedded realtime systems, for which jitter is typically an important factor. This paper investigates whether it is possible to guarantee certain amount of jitter for a given set of applications on a shared platform. The effect of jitter on the stability of control applications and its relation with the latency will be discussed. The importance arises from the fact that it is considerably easier to manage the constant part of the delay (known as latency), while the process of coping with the varying part of the delay (known as jitter) is more involved. The proposed solution guarantees certain jitter limits, and at the same time does not lead to overly pessimistic latency values. The results are later used in a design optimization problem to minimize the resource utilized.
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| 2. |
- Imes, Connor, et al.
(författare)
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POET: A Portable Approach to Minimizing Energy Under Soft Real-time Constraints
- 2015
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Ingår i: Real-Time and Embedded Technology and Applications Symposium (RTAS), 2015 IEEE. - 1545-3421. - 9781479986033 - 9781479986040 ; , s. 75-86
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Konferensbidrag (refereegranskat)abstract
- Embedded real-time systems must meet timing constraints while minimizing energy consumption. To this end, many energy optimizations are introduced for specific platforms or specific applications. These solutions are not portable, however, and when the application or the platform change, these solutions must be redesigned. Portable techniques are hard to develop due to the varying tradeoffs experienced with different application/platform configurations. This paper addresses the problem of finding and exploiting general tradeoffs, using control theory and mathematical optimization to achieve energy minimization under soft real-time application constraints. The paper presents POET, an open-source C library and runtime system that takes a specification of the platform resources and optimizes the application execution. We test POET's ability to deliver portable energy reduction on two embedded systems with different tradeoff spaces - the first with a mobile Intel Haswell processor, and the second with an ARM big.LITTLE System on Chip. POET achieves the desired latency goals with small error while consuming, on average, only 1.3% more energy than the dynamic optimal oracle on the Haswell and 2.9% more on the ARM. We believe this open-source, library-based approach to resource management will simplify the process of writing portable, energy-efficient code for embedded systems.
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| 3. |
- Khalilzad, Nima, et al.
(författare)
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A Feedback Scheduling Framework for Component-Based Soft Real-Time Systems
- 2015
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Ingår i: 21th IEEE Real-Time and Embedded Technology and Applications Symposium RTAS'15. - 9781479986033 ; , s. 182-193
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Konferensbidrag (refereegranskat)abstract
- Component-based software systems with real-time requirements are often scheduled using processor reservation techniques. Such techniques have mainly evolved around hard real-time systems in which worst-case resource demands are considered for the reservations. In soft real-time systems, reserv- ing the processors based on the worst-case demands results in unnecessary over-allocations. In this paper, targeting soft real-time systems running on multiprocessor platforms, we focus on components for which processor demand varies during run-time. We propose a feedback scheduling frameworkwhere processor reservations are used for scheduling components. The reservation bandwidths as well as the reservation periods are adapted using MIMO LQR controllers. We provide an allocation mechanism for distributing components over processors. The proposed framework is implemented in the TrueTime simulation tool for system identification. We use a case study to investigate the performance of our framework in the simulation tool. Finally, the framework is implemented in the Linux kernel for practical evaluations. The evaluation results suggest that the framework can efficiently adapt the reservation parameters during run-time by imposing negligible overhead.
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| 4. |
- Kim, Hokeun, et al.
(författare)
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A Predictable and Command- Level Priority-Based DRAM Controller for Mixed-Criticality Systems
- 2015
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Ingår i: Proceedings of the 21th IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS). - : IEEE Press. - 9781479986033 ; , s. 317-326
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Konferensbidrag (refereegranskat)abstract
- Mixed-criticality systems have tasks with different criticality levels running on the same hardware platform. Today's DRAM controllers cannot adequately satisfy the often conflicting requirements of tightly bounded worst-case latency for critical tasks and high performance for non-critical real-time tasks. We propose a DRAM memory controller that meets these requirements by using bank-aware address mapping and DRAM command-level priority-based scheduling with preemption. Many standard DRAM controllers can be extended with our approach, incurring no performance penalty when critical tasks are not generating DRAM requests. Our approach is evaluated by replaying memory traces obtained from executing benchmarks on an ARM ISA-based processor with caches, which is simulated on the gem5 architecture simulator. We compare our approach against previous TDM-based approaches, showing that our proposed memory controller achieves dramatically higher performance for non-critical tasks, without any significant impact on the worstcase latency of critical tasks.
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| 5. |
- Pathan, Risat, 1979
(författare)
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Unifying Fixed- and Dynamic-Priority Scheduling based on Priority Promotion and an Improved Ready Queue Management Technique
- 2015
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Ingår i: Proceedings of the IEEE Real-Time and Embedded Technology and Applications Symposium, RTAS. - 1545-3421. - 9781479986033 ; 2015-May:Art nr. 7108444, s. 209-220
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a new preemptive scheduling algorithm, called Fixed-Priority with Priority Promotion (FPP), for scheduling sporadic tasks on uni- and multiprocessor platform. In FPP scheduling, tasks are executed similar to traditional fixed-priority (FP) scheduling but the priority of some tasks may be promoted at fixed time interval (called, promotion point) relative to the release time of each job. A policy called Increase Priority at Deadline Difference (IPDD) to compute the promotion points and promoted priorities for each task is proposed. It is shown that when all tasks' priorities are governed under IPDD policy, then FPP scheduling essentially prioritizes jobs according to Earliest-Deadline-First (EDF) priority. It is known that inserting and removing jobs to and from the ready queue of traditional EDF scheduler is more complex and has higher overhead than that of FP scheduler. To avoid such problem in FPP scheduling, a simple data structure and efficient operations to insert and remove jobs to and from the ready queue are proposed. Finally, an effective scheme to reduce overhead due to priority promotion is proposed: if a task set is not schedulable using traditional FP scheduling, then promotion points are assigned only to those tasks that need them to meet the deadlines; otherwise, tasks are assigned fixed priorities without any priority promotion and executed same as traditional FP scheduling. Empirical investigation shows the effectiveness of the proposed scheme in reducing overhead on uniprocessor and in accepting larger number of task sets in comparison to that of using state-of-the-art global schedulability tests for multiprocessors. © 2015 IEEE.
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