Energy-efficient Real-time Task Scheduling Research Articles

Energy-Efficient Scheduling of Real-Time Tasks in Reconfigurable Homogeneous Multicore Platforms

This paper deals with real-time scheduling of homogeneous multicore platforms powered by a battery to be periodically recharged. A system is composed of reconfigurable real-time dependent and periodic tasks to be assigned to different cores interconnected by a network-on-chip (NoC). The system is subject to reconfigurations, which are automatic operations allowing the addition and/or removal of tasks as well as their exchanged messages on the NoC. Consequently, any reconfiguration can violate real-time and energy constraints on cores as well as the NoC when the energy is unavailable until the next recharge. A novel periodic task model based on elastic coefficients and a new scheduling strategy are proposed to compute useful temporal parameters allowing for tasks and messages to meet the related constraints while controlling the communication cost on the NoC. This strategy is compared with an integer linear programming-based optimal solution, and a tool named OptimalMappingTasks is developed to run different simulations that prove the originality of this paper’s contribution.

IASA: an energy-efficient scheduling algorithm for real-time tasks with lock-free objects

In this paper, we are interested in the energy-efficient scheduling of real-time tasks which may access lock-free objects in a non-ideal DVS processor. Compared to conventional lock-based real-time synchronisation protocols, lock-free objects have the advantage of the avoidance of priority inversion and deadlock. However, because lock-free objects permit concurrent operations to interfere with each other, the access to a lock-free object might take an arbitrarily long time to complete owing to repeated interferences. In this paper, we propose an algorithm, called interference-aware speed assignment (IASA), for scheduling of real-time tasks with lock-free objects. The IASA assigns proper execution speeds to tasks scheduled by the earliest deadline first (EDF) scheduling policy. The execution speeds are calculated based on the schedulability analysis of the EDF policy with the cost of the interferences of lock-free objects. As a result, the energy consumption can be reduced while meeting the timing constraints of real-time tasks.

Energy-efficient scheduling of real-time tasks with shared resources

This paper explores the energy-efficient scheduling of real-time tasks on a non-ideal DVS processor in the presence of resource sharing. We assume that tasks are periodic, preemptive and may access to shared resources. When dynamic-priority and fixed-priority scheduling are considered, we use the earliest deadline first (EDF) algorithm and the rate monotonic (RM) algorithm to schedule the given set of tasks. Based on the stack resource policy (SRP), we propose an approach, called blocking-aware two-speed (BATS) algorithm, to synchronize the tasks with shared resources and to calculate appropriate execution speeds so that the shared resources can be accessed in a mutual exclusive manner and the energy consumption can be reduced. Particularly, BATS uses a static low speed to execute tasks initially, and then it switches to a high speed dynamically whenever a task blocks a higher priority task. More specifically, the processor runs at the high speed from the beginning of the blocking until the deadline of the blocked task or the processor becomes idle. In order to guarantee that the deadlines of tasks are met, the static low speed and the dynamic high speeds are derived based on the theoretical analysis of the schedulability of tasks. Compared with existing work, BATS achieves more energy saving because its dynamic high speeds are lower than that of existing work and the processor has less chance to execute tasks at the high speeds. The schedulability analysis and the properties of our proposed BATS are provided in this paper. We also evaluated the capabilities of BATS by a series of experiments, for which we have some encouraging results.

On-line energy-efficient real-time task scheduling for a heterogeneous dual-core system-on-a-chip

Abstract On-line energy-efficient real-time task scheduling for a heterogeneous dual-core system-on-a-chip is a challenging problem due to precedence constraints and the varied properties of the general-purpose processor core and the synergistic processor core. This study proposes an on-line heterogeneous dual-core energy-efficient scheduling framework for dynamic workloads with real-time constraints. The energy efficiency ratio is presented to manage energy consumption while considering of the varied properties of the cores, while precedence constraints among the tasks are dealt with through interaction between bandwidth servers. This framework is configurable for low energy consumption and high system utilization. The capability of the proposed methodology is evaluated by a series of experiments and the results obtained are encouraging.

Data Transmission with the Battery Utilization Maximization

With the growing popularity of 3G-powered devices, there are growing demands on energy-efficient data transmission strategies for various embedded systems. Different from the past work in energy-efficient real-time task scheduling, we explore strategies to maximize the amount of data transmitted by a 3G module under a given battery capacity. In particular, we present algorithms under different workload configurations with and without timing constraint considerations. Experiments were then conducted to verify the validity of the strategies and develop insights in energy-efficient data transmission.

Energy-Efficient Task Synchronization for Real-Time Systems

In the past decade, energy-efficient real-time task scheduling has been widely explored in the form of various optimization problems. This paper considers energy-efficient real-time task synchronization protocols and the overhead of frequency switching in real systems design. We propose the concept of frequency locking to better manage the cost in frequency switching. To minimize the energy consumption and meet the timing constraints, algorithms are presented to assign tasks base frequencies under existing synchronization protocols which are then extended with the frequency locking concept. Finally, a series of extensive simulations is performed and a real case study is presented to evaluate the proposed methodology and obtain comparison studies using different workloads and protocols.

Energy Efficient Scheduling of Real-Time Tasks on Multicore Processors

Multicore processors deliver a higher throughput at lower power consumption than unicore processors. In the near future, they will thus be widely used in mobile real-time systems. There have been many research on energy-efficient scheduling of real-time tasks using DVS. These approaches must be modified for multicore processors, however, since normally all the cores in a chip must run at the same performance level. Thus, blindly adopting existing DVS algorithms that do not consider the restriction will result in a waste of energy. This article suggests Dynamic Repartitioning algorithm based on existing partitioning approaches of multiprocessor systems. The algorithm dynamically balances the task loads of multiple cores to optimize power consumption during execution. We also suggest Dynamic Core Scaling algorithm, which adjusts the number of active cores to reduce leakage power consumption under low load conditions. Simulation results show that Dynamic Repartitioning can produce energy savings of about 8 percent even with the best energy-efficient partitioning algorithm. The results also show that Dynamic Core Scaling can reduce energy consumption by about 26 percent under low load conditions.