Energy saving and system reliability are two crucial issues for designing modern multiprocessor systems. There has been reliability-aware power management with dynamic voltage–frequency scaling (DVFS) schemes in recent studies. However, they are limited to optimization under the impact of DVFS on energy and reliability and have not considered reducing the non-negligible leakage energy consumption. In this paper, we focus on co-management of system reliability and total energy for applications with precedence constrained tasks on heterogeneous multiprocessor real-time systems. We first investigate the impact of energy management techniques on both reliability and energy of the systems using task recovery for fault tolerance and then propose an Energy-efficient Fault-tolerant Scheduling (EFS) scheme integrated with power mode management, which can mitigate the negative impact of DVFS on system reliability. To obtain the optimal energy-efficient reliability-guaranteed scheduling for pre-mapped applications on systems considering various realistic issues, we build mixed integer linear programing formulations with the proposed EFS scheme. To address mapping and scheduling for energy-efficiency and fault-tolerance, we finally develop a framework implemented by a List-based Binary Particle Swarm Optimization algorithm. The extensive comparative evaluations for synthetic and realistic benchmarks show that our approaches outperform several related studies in terms of energy consumption and system reliability.

A linear and exponential (sqrt2 rule) combined curve fitting (CF) is proposed for low-energy shared cache partitioning. Considering cache’s inherent characteristics between cache miss rate and its size, function with an exponent of (1-sqrt2) fits the region of non-linear high-utility cache size, while linear function fits both regions of linear high-utility and low-utility cache size. Using the fitted functions, we proposed a scheme with purely mathematical formulization of energy consumption, which helps fast and efficient shared cache partition. Experimental results show that CF based shared cache partitioning scheme achieves up to 34.5% energy savings compared with other traditional techniques. Moreover, our approach has a high prediction accuracy for the shared cache miss rate and the energy.

Energy optimization for periodic applications running on safety/time-critical time-triggered multiprocessor systems has been studied recently. An interesting feature of the applications on the systems is that some tasks are strictly periodic while others are non-strictly periodic, i.e., the start time interval between any two successive instances of the same task is not fixed as long as task deadlines can be met. Energy-efficient scheduling of such applications on the systems has, however, been rarely investigated. In this paper, we focus on the problem of static scheduling multiple periodic applications consisting of both strictly and non-strictly periodic tasks on safety/time-critical time-triggered multiprocessor systems for energy minimization. The challenge of the problem is that both strictly and non-strictly periodic tasks must be intelligently addressed in scheduling to optimize energy consumption. We introduce a new practical task model to characterize the unique feature of specific tasks, and formulate the energy-efficient scheduling problem based on the model. Then, an improved Mixed Integer Linear Programming (MILP) method is proposed to obtain the optimal scheduling solution by considering strict and non-strict periodicity of the specific tasks. To decrease the high complexity of MILP, we also develop a heuristic algorithm to efficiently find a high-quality solution in reasonable time. Extensive evaluation results demonstrate the proposed MILP and heuristic methods can on average achieve about 14.21% and 13.76% energy-savings respectively compared with existing work.

Energy optimization plays an increasingly critical role in designing an embedded real-time multiprocessor System on Chip (MPSoC). Dynamic Voltage Frequency Scaling (DVFS) and Dynamic Power Management (DPM) are preferable techniques to optimize energy consumption. However, previous DVFS and DPM algorithms were mostly designed for inter-task scheduling, without sufficient exploration on intra-task scheduling for further energy reduction. This paper presents a new intra-task scheduling approach considering the probabilistic distribution of task execution time, and it optimizes the mathematical expectation of power consumption (expected power consumption) for periodic dependent tasks with uncertain execution time running on MPSoCs using DVFS and DPM. The energy-efficient scheduling problem can be formulated by means of mixed integer linear programming (MILP) with the proposed technique. Moreover, we also propose a technique to compress the exploration space by reorganizing the probabilistic profiling information of all tasks. Our experimental results on synthetic and realistic benchmarks show that the proposed approach achieves up to 30% energy savings compared with other existing methods.

Cache partitioning is a successful technique for saving energy for a shared cache and all the existing studies focus on multi-program workloads running in multicore systems. In this paper, we are motivated by the fact that a multi-thread application generally executes faster than its single-thread counterpart and its cache accessing behavior is quite different. Based on this observation, we study applications running in multi-thread mode and classify data of the multi-thread applications into shared and private categories, which helps reduce the interferences among shared and private data and contributes to constructing a more efficient cache partitioning scheme. We also propose a hardware structure to support these operations. Then, an access adaptive and thread-aware cache partitioning (ATCP) scheme is proposed, which assigns separate cache portions to shared and private data to avoid the evictions caused by the conflicts from the data of different categories in the shared cache. The proposed ATCP achieves a lower energy consumption, meanwhile improving the performance of applications compared with the least recently used (LRU) managed, core-based evenly partitioning (EVEN) and utility-based cache partitioning (UCP) schemes. The experimental results show that ATCP can achieve 29.6% and 19.9% average energy savings compared with LRU and UCP schemes in a quad-core system. Moreover, the average speedup of multi-thread ATCP with respect to single-thread LRU is at 1.89.