Results 1  10
of
23
Feedback edf scheduling exploiting dynamic voltage scaling
 In IEEE RealTime Embedded Technology and Applications Symposium
, 2004
"... Dynamic voltage scaling (DVS) is a promising method for embedded systems to exploit multiple voltage and frequency levels and to prolong battery life. However, pure DVS techniques do not perform well for systems with dynamic workloads where the job execution times vary significantly. In this paper, ..."
Abstract

Cited by 73 (9 self)
 Add to MetaCart
(Show Context)
Dynamic voltage scaling (DVS) is a promising method for embedded systems to exploit multiple voltage and frequency levels and to prolong battery life. However, pure DVS techniques do not perform well for systems with dynamic workloads where the job execution times vary significantly. In this paper, we present a novel approach combining feedback control with DVS schemes targeting hard realtime systems with dynamic workloads. Our method relies strictly on operating system support by integrating a DVS scheduler and a feedback controller within the EDF scheduling algorithm. Each task is divided into two portions. Within the first portion, the objective is to exploit frequency scaling for the average execution time. We reserve enough time for the second portion to meet the deadline requirements up to the worstcase execution time following a lastchance approach. Feedback techniques make the system capable to select the right frequency and voltage settings for the first potion, as well as guaranteeing hard realtime requirements for the overall task. Simulation experiments demonstrate the ability of our algorithm to save up to 29 % more energy than previous work for task sets with different dynamic workload characteristics. 1.
Speed Modulation in EnergyAware RealTime Systems
, 2005
"... This paper presents a general framework for analyzing and designing embedded systems with energy and timing requirements. A set of realistic assumptions is considered in the model in order to apply the results in practical realtime applications. For example, the processor is assumed to have as a set ..."
Abstract

Cited by 37 (10 self)
 Add to MetaCart
This paper presents a general framework for analyzing and designing embedded systems with energy and timing requirements. A set of realistic assumptions is considered in the model in order to apply the results in practical realtime applications. For example, the processor is assumed to have as a set of discrete operating modes, each characterized by speed, power consumption. The transition delay between modes is considered. To take I/O operations into account, task computation times are modeled with a part that scales with the speed and a part having a fixed duration. Given a set of realtime tasks, the proposed method allows to compute the optimal sequence of voltage/speed changes that approximates the minimum continuous speed which guarantees the feasibility of the system. The analysis is performed both under fixed and dynamic priority assignments.
Reactive speed control in temperatureconstrained realtime systems
 RealTime Systems Journal
, 2008
"... In this paper, we study temperatureconstrained realtime systems, where realtime guarantees must be met without exceeding safe temperature levels within the processor. We give a short review on temperature issues in processors and describe how speed control can be used to tradeoff task delays ag ..."
Abstract

Cited by 32 (4 self)
 Add to MetaCart
(Show Context)
In this paper, we study temperatureconstrained realtime systems, where realtime guarantees must be met without exceeding safe temperature levels within the processor. We give a short review on temperature issues in processors and describe how speed control can be used to tradeoff task delays against processor temperature. In this paper, we describe how traditional worstcase execution scenarios do not apply in temperatureconstrained situations. As example, we adopt a simple reactive speed control technique. We show how this simple reactive scheme can improve the processor utilization compared with any constantspeed scheme. 1
Minimizing CPU Energy in RealTime Systems with Discrete Speed Management
, 2008
"... This paper presents a general framework to analyze and design embedded systems minimizing the energy consumption without violating timing requirements. A set of realistic assumptions is considered in the model in order to apply the results in practical realtime applications. The processor is assume ..."
Abstract

Cited by 11 (1 self)
 Add to MetaCart
This paper presents a general framework to analyze and design embedded systems minimizing the energy consumption without violating timing requirements. A set of realistic assumptions is considered in the model in order to apply the results in practical realtime applications. The processor is assumed to have as a set of discrete operating modes, each characterized by speed and power consumption. The energy overhead and the transition delay incurred during mode switches are considered. Task computation times are modeled with a part that scales with the speed and a part having a fixed duration, to take I/O operations into account. The proposed method allows to compute the optimal sequence of voltage/speed changes that approximates the minimum continuous speed which guarantees the feasibility of a given set of realtime tasks, without violating the deadline constraints. The analysis is performed both under fixed and dynamic priority assignments.
A Resource Reservation Algorithm for PowerAware Scheduling of Periodic and Aperiodic RealTime Tasks
 IEEE Trans. Computers
, 2006
"... Abstract—Power consumption is an important issue in the design of realtime embedded systems. As many embedded systems are powered by batteries, the goal is to extend the autonomy of the system as much as possible. To reduce power consumption, modern processors can change their voltage and frequency ..."
Abstract

Cited by 7 (0 self)
 Add to MetaCart
(Show Context)
Abstract—Power consumption is an important issue in the design of realtime embedded systems. As many embedded systems are powered by batteries, the goal is to extend the autonomy of the system as much as possible. To reduce power consumption, modern processors can change their voltage and frequency at runtime. A poweraware scheduling algorithm can exploit this capability to reduce power consumption while preserving the timing constraints of realtime tasks. In this paper, we present GRUBPA, a novel poweraware scheduling algorithm based on a resource reservation technique. In addition to providing temporal isolation and time guarantees and, unlike most of the poweraware algorithms proposed in the literature, GRUBPA can efficiently handle systems consisting of both hard and soft, aperiodic, sporadic, and periodic tasks. We compared our algorithm with existing poweraware scheduling algorithms on an extensive set of simulation experiments on synthetic task sets. The results show that the performance of our algorithm is in line with the stateoftheart poweraware algorithms. We also present the implementation of our algorithm in the Linux operating system and discuss practical implementation issues like switching overhead and power models. Finally, we show the results of experiments performed on a real testbed application. Index Terms—DVS, realtime, resourcereservation, scheduling, poweraware. Ç
ParaScale: Exploiting Parametric Timing Analysis for RealTime Schedulers and Dynamic Voltage Scaling
 Proceedings of the IEEE RealTime Systems Symposium
, 2005
"... Static timing analysis safely bounds worstcase execution times to determine if tasks can meet their deadlines in hard realtime systems. However, conventional timing analysis requires that the upper bound of loops be known statically, which limits its applicability. Parametric timing analysis metho ..."
Abstract

Cited by 5 (3 self)
 Add to MetaCart
(Show Context)
Static timing analysis safely bounds worstcase execution times to determine if tasks can meet their deadlines in hard realtime systems. However, conventional timing analysis requires that the upper bound of loops be known statically, which limits its applicability. Parametric timing analysis methods remove this constraint by providing the WCET as a formula parameterized on loop bounds. This paper contributes a novel technique to allow parametric timing analysis to interact with dynamic realtime schedulers. By dynamically detecting actual loop bounds, a lower WCET bound can be calculated, onthefly, for the remaining execution of a task. We analyze the benefits from parametric analysis in terms of dynamically discovered slack in a schedule. We then assess the potential for dynamic power conservation by exploiting parametric loop bounds for ParaScale, our intratask dynamic voltage scaling (DVS) approach. Our results demonstrate that the parametric approach to timing analysis provides 66%80% additional savings in power consumption. We further show that using this approach combined with online intratask DVS to exploit parametric execution times results in much lower power consumption. Hence, even in the absence of dynamic scheduling, significant savings in power can be obtained, e.g., in the case of cyclic executives. 1.
Optimal Speed Assignment for Probabilistic Execution Times
 In 2 nd Workshop on PowerAware RealTime Computing (PARC’05), NJ
, 2005
"... The problem of reducing energy consumption is dominating the design and the implementation of embedded realtime systems. For this reason, a new generation of processors allow to vary the voltage and the operating frequency to balance computational speed versus energy consumption. The policies that c ..."
Abstract

Cited by 5 (3 self)
 Add to MetaCart
(Show Context)
The problem of reducing energy consumption is dominating the design and the implementation of embedded realtime systems. For this reason, a new generation of processors allow to vary the voltage and the operating frequency to balance computational speed versus energy consumption. The policies that can exploit this feature are called Dynamic Voltage Scheduling (DVS). In realtime systems, the DVS technique must also provide the worstcase computational requirement. However, it is well known that the probability of a task executing for the longest possible time is very low. Hence, DVS policies can exploit probabilistic information about the execution times of tasks to reduce the energy consumed by the processor. In this paper we provide the foundations to integrate probabilistic timing analysis with energy minimization techniques, starting from the simple case of one task. 1
Parametric Timing Analysis and Its Application to Dynamic Voltage Scaling
, 2010
"... Embedded systems with realtime constraints depend on a priori knowledge of worstcase execution times (WCETs) to determine if tasks meet deadlines. Static timing analysis derives bounds on WCETs but requires statically known loop bounds. This work removes the constraint on known loop bounds through ..."
Abstract

Cited by 3 (2 self)
 Add to MetaCart
Embedded systems with realtime constraints depend on a priori knowledge of worstcase execution times (WCETs) to determine if tasks meet deadlines. Static timing analysis derives bounds on WCETs but requires statically known loop bounds. This work removes the constraint on known loop bounds through parametric analysis expressing WCETs as functions. Tighter WCETs are dynamically discovered to exploit slack by dynamic voltage scaling (DVS) saving 60 % to 82 % energy over DVSoblivious techniques and showing savings close to more costly dynamicpriority DVS algorithms. Overall, parametric analysis expands the class of realtime applications to programs with loopinvariant dynamic loop bounds while retaining tight WCET bounds.
Exploiting Dynamic Workload Variation in Low Energy Preemptive Task Scheduling
"... A novel energy reduction strategy to maximally exploit the dynamic workload variation is proposed for the offline voltage scheduling of preemptive systems. The idea is to construct a fullypreemptive schedule that leads to minimum energy consumption when the tasks take on approximately the average e ..."
Abstract

Cited by 2 (0 self)
 Add to MetaCart
(Show Context)
A novel energy reduction strategy to maximally exploit the dynamic workload variation is proposed for the offline voltage scheduling of preemptive systems. The idea is to construct a fullypreemptive schedule that leads to minimum energy consumption when the tasks take on approximately the average execution cycles yet still guarantees no deadline violation during the worstcase scenario. Endtime for each subinstance of the tasks obtained from the schedule is used for the online dynamic voltage scaling (DVS) of the tasks. For the tasks that normally require a small number of cycles but occasionally a large number of cycles to complete, such a schedule provides more opportunities for slack utilization and hence results in larger energy saving. The concept is realized by formulating the problem as a NonLinear Programming (NLP) optimization problem. Experimental results show that, by using the proposed scheme, the total energy consumption at runtime is reduced by as high as 60 % for randomly generated task sets when comparing with the static scheduling approach only using worst case workload. 1.
Dynamic Voltage Scaling with Feedback EDF Scheduling for Realtime Embedded Systems
, 2005
"... Dynamic voltage scaling (DVS) is a promising method to reduce the power consumption of CMOSbased embedded processors. However, pure DVS techniques do not perform well for dynamic systems where the execution times of different jobs vary significantly. A novel DVS scheme with feedback control mechan ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
Dynamic voltage scaling (DVS) is a promising method to reduce the power consumption of CMOSbased embedded processors. However, pure DVS techniques do not perform well for dynamic systems where the execution times of different jobs vary significantly. A novel DVS scheme with feedback control mechanisms for hard realtime systems is proposed in this work. It produces energyefficient schedules for both static and dynamic workloads. Tasksplitting, slackpassing and preemptionhandling schemes are proposed to aggressively reduce the speed of each task. Different feedback control structures are integrated into the DVS algorithm to make it adaptable to workload variations. This scheme relies strictly on operating system support. It is evaluated in simulation as well as on an embedded platform. For given task sets, simulation experiments demonstrate the benefits of this scheme with savings of up to 29 % in energy over previous work. This scheme exhibits up to 24 % additional energy savings over other DVS algorithms on the embedded platform. The feedbackbased DVS scheme is further extended to be leakage aware, which considers not only dynamic but also static power consumption caused by leakage current in circuits. A