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The interconnection network comprises a significant portion of the cost of large parallel computers, both in economic terms and power consumption. Several previous proposals exploit large-radix routers to build scalable low-distance topologies with the aim of minimizing these costs. However, they fail to consider potential unbalance in the network utilization, which in some cases results in suboptimal designs. Based on an appropriate cost model, this paper advocates the use of networks based on incidence graphs of projective planes, broadly denoted as Projective Networks. Projective Networks rely on generalized Moore graphs with uniform link utilization and encompass several proposed direct (PN and demi-PN) and indirect (OFT) topologies under a common mathematical framework. Compared to other proposals with average distance between 2 and 3 hops, these networks provide very high scalability while preserving a balanced network utilization, resulting in low network costs. [ABSTRACT FROM PUBLISHER]

Heterogenerous multi-cores utilize the strength of different architectures for executing particular types of workload, and usually offer higher performance and energy efficiency. In this paper, we study the worst-case response time (WCRT) analysis of typed scheduling of parallel DAG tasks on heterogeneous multi-cores, where the workload of each vertex in the DAG is only allowed to execute on a particular type of cores. The only known WCRT bound for this problem is grossly pessimistic and suffers the non-self-sustainability problem. In this paper, we propose two new WCRT bounds. The first new bound has the same time complexity as the existing bound, but is more precise and solves its non-self-sustainability problem. The second new bound explores more detailed task graph structure information to greatly improve the precision, but is computationally more expensive. We prove that the problem of computing the second bound is strongly NP-hard if the number of types in the system is a variable, and develop an efficient algorithm which has polynomial time complexity if the number of types is a constant. Experiments with randomly generated workload show that our proposed new methods are more precise than the existing bound while having good scalability. [ABSTRACT FROM AUTHOR]

The article discusses various topics published within the issue including one on design power-efficient architectures, one on prioritizing power saving among various computer components, and one on developing means of saving system-wide energy.

The dramatic increasing of data and demands for computing capabilities may result in excessive use of resources in cloud data centers, which not only causes the raising of energy consumption, but also leads to the violation of Service Level Agreement (SLA). Dynamic consolidation of virtual machines (VMs) is proven to be an efficient way to tackle this issue. In this paper, we present an Adaptive Deep Reinforcement Learning (DRL)-based Virtual Machine Consolidation (ADVMC) framework for energy-efficient cloud data centers. ADVMC has two phases. In the first phase, Influence Coefficient is introduced to measure the impact of a VM on producing host overload, and a dynamic Influence Coefficient-based VM selection algorithm (ICVMS) is proposed to preferentially choose those VMs with the greatest impact for migration in order to remove the excessive workloads of the overloaded host quickly and accurately. In the second phase, a Prediction Aware DRL-based VM placement method (PADRL) is further proposed to automatically find suitable hosts for VMs to be migrated, in which a state prediction network is designed based on LSTM to provide DRL-based model more reasonable environment states so as to accelerate the convergence of DRL. Simulation experiments on the real-world workload provided by Google Cluster Trace have shown that our ADVMC approach can largely cut down system energy consumption and reduce SLA violation of users as compared to many other VM consolidation policies. [ABSTRACT FROM AUTHOR]

GPUs are widely used to accelerate the training of machine learning workloads. As modern machine learning models become increasingly larger, they require a longer time to train, leading to higher GPU energy consumption. This paper presents GPOEO, an online GPU energy optimization framework for machine learning training workloads. GPOEO dynamically determines the optimal energy configuration by employing novel techniques for online measurement, multi-objective prediction modeling, and search optimization. To characterize the target workload behavior, GPOEO utilizes GPU performance counters. To reduce the performance counter profiling overhead, it uses an analytical model to detect the training iteration change and only collects performance counter data when an iteration shift is detected. GPOEO employs multi-objective models based on gradient boosting and a local search algorithm to find a trade-off between execution time and energy consumption. We evaluate the GPOEO by applying it to 71 machine learning workloads from two AI benchmark suites running on an NVIDIA RTX3080Ti GPU. Compared with the NVIDIA default scheduling strategy, GPOEO delivers a mean energy saving of 16.2% with a modest average execution time increase of 5.1%. [ABSTRACT FROM AUTHOR]

The majority of large-scale data intensive applications executed by data centers are based on MapReduce or its open-source implementation, Hadoop. Such applications are executed on large clusters requiring large amounts of energy, making the energy costs a considerable fraction of the data center’s overall costs. Therefore minimizing the energy consumption when executing each MapReduce job is a critical concern for data centers. In this paper, we propose a framework for improving the energy efficiency of MapReduce applications, while satisfying the service level agreement (SLA). We first model the problem of energy-aware scheduling of a single MapReduce job as an Integer Program. We then propose two heuristic algorithms, called energy-aware MapReduce scheduling algorithms (EMRSA-I and EMRSA-II), that find the assignments of map and reduce tasks to the machine slots in order to minimize the energy consumed when executing the application. We perform extensive experiments on a Hadoop cluster to determine the energy consumption and execution time for several workloads from the HiBench benchmark suite including TeraSort, PageRank, and K-means clustering, and then use this data in an extensive simulation study to analyze the performance of the proposed algorithms. The results show that EMRSA-I and EMRSA-II are able to find near optimal job schedules consuming approximately 40 percent less energy on average than the schedules obtained by a common practice scheduler that minimizes the makespan. [ABSTRACT FROM AUTHOR]

Networks-on-chip (NoCs) acquired substantial advancements as the typical solution for a modular, flexible and high performance communication infrastructure coping with the scalable Multi-/Manycores technology. However, the increasing chip complexity heading towards thousand cores, together with the approaching dark-silicon era, puts energy efficiency as an integral design key for future NoC-based multicores, where NoCs are significantly contributing to the total chip power. In this paper, we propose HPPT-NoC, a dark-silicon inspired energy-efficient hierarchical TDM NoC with online distributed setup-scheme. The proposed network makes use of the dim silicon parts of the chip to hierarchically connect quad-routers units. Normal routers operate at full-chip-frequency at high supply level, and hierarchical routers operate at half-chip-frequency and lower supply voltage with adequate synchronization. Routers follow a proposed TDM architecture that separates the datapath from the control-setup planes. This allows separate clocking and operating supplies between data and control and to keep the control-setup as a single-slot-cycle design independent of the datapath slot size. The proposed NoC architecture is evaluated versus a base NoC from the state-of-the-art in terms of performance and hardware results using Synopsys VCS and Synopsys Design Compiler for SAED90nm and SAED32nm technologies. The obtained results highlight the power-frequency-trading feature supported by the proposed hierarchical NoC through the configurable data-control clock relation and maintained over the different technology nodes. With the same power budget of the base NoC, the proposed architecture provides up to 74% setup latency enhancement, 32% increased NoC saturation load, and 21% higher success rates, offering up to 78% improved power delay product. On the other hand, with 38% power savings, the proposed NoC provides up to 37% enhanced latency and 15% higher success rates, with 72% enhanced power delay product. The proposed design consumes almost double the area of the base NoC, however with an average of 56% under-clocked (dim) silicon area operating at half to quarter the maximum chip frequency. This results in reduced power density as a main concern in the dark-silicon era down to 24% of the base NoC. [ABSTRACT FROM AUTHOR]

With the advanced communication sensors are deployed into the modern connected vehicles (CVs), large amounts of traffic information can be collected in real-time, which gives the chance to explore the various techniques to control the routing of CVs in a ground traffic network. However, the control of CVs often suffers from energy inefficiency due to the constant changes of network capacity and traffic demand. In this paper, we propose a cost-based iterative framework, named EEPC, to explore the energy-efficient parallel control of connected vehicles. EEPC enables the control of CVs to iteratively generate a feasible solution, where the control of each vehicle is guided in an energy-efficient way routing on its own trajectory. EEPC eliminates the conflicts between CVs with a limited number of iterations and in each iteration, EEPC enables each vehicle to coordinate with other vehicles for a same road resource of the traffic network, further determining which vehicle needs the resource most. Note that at each iteration, the imposed cost is updated to guide the coordination between CVs while the energy is always used to guide the control of CVs in EEPC. In addition, we also explore the parallel control of CVs to improve the real-time performance of EEPC. We provide two parallel approaches, one is fine grain and the other is coarse grain. The fine grain performs the parallel control of single-vehicle routing while the coarse grain performs the parallel control of multi-vehicle routing. Note that fine grain adopts multi-threading techniques and coarse grain adopts MPI techniques. The simulation results show that the proposed EEPC can generate a feasible control solution. Notably, we also demonstrate that the generated solution is effective in eliminating the resource conflicts between CVs and in suggesting an energy-efficient route to each vehicle. To the best of our knowledge, this is the first work to explore energy-efficient parallel control of CVs. [ABSTRACT FROM AUTHOR]

Task offloading is a promising technology to exploit the available computational resources in spatially distributed fog nodes efficiently in the era of fog computing. In this paper, we look for an online task offloading strategy to minimize the long-term cost, which factors in the latency, the energy consumption, and the switching cost. To this end, we formulate a stochastic programming problem and the expectations of the system parameters are allowed to change abruptly at unknown time instants. Meanwhile, we consider the fact that the queried nodes can only feed back the processing results after finishing the tasks. Then we put forth an effective bandit learning algorithm, i.e., the BLOT, to solve this challenging stochastic programming under the non-stationary bandit model. We also demonstrate that our proposed BLOT algorithm is asymptotically optimal in a non-stationary fog-enabled network. Numerical experiments further verify the superb performance of BLOT. [ABSTRACT FROM AUTHOR]

With the development of computer architecture, even for embedded systems, GPU devices can be integrated, providing outstanding performance and energy efficiency to meet the requirements of different industries, applications, and deployment environments. Data analytics is an important application scenario for embedded systems. Unfortunately, due to the limitation of the capacity of the embedded device, the scale of problems handled by the embedded system is limited. In this paper, we propose a novel data analytics method, called G-TADOC, for efficient text analytics directly on compression on embedded GPU systems. A large amount of data can be compressed and stored in embedded systems, and can be processed directly in the compressed state, which greatly enhances the processing capabilities of the systems. Particularly, G-TADOC has three innovations. First, a novel fine-grained thread-level workload scheduling strategy for GPU threads has been developed, which partitions heavily-dependent loads adaptively in a fine-grained manner. Second, a GPU thread-safe memory pool has been developed to handle inconsistency with low synchronization overheads. Third, a sequence-support strategy is provided to maintain high GPU parallelism while ensuring sequence information for lossless compression. Moreover, G-TADOC involves special optimizations for embedded GPUs, such as utilizing the CPU-GPU shared unified memory. Experiments show that G-TADOC provides 13.2× average speedup compared to the state-of-the-art TADOC. G-TADOC also improves performance-per-cost by 2.6× and energy efficiency by 32.5× over TADOC. [ABSTRACT FROM AUTHOR]

Due to the increasing usage of cloud computing applications, it is important to minimize energy cost consumed by a data center, and simultaneously, to improve quality of service via data center management. One promising approach is to switch some servers in a data center to the idle mode for saving energy while to keep a suitable number of servers in the active mode for providing timely service. In this paper, we design both online and offline algorithms for this problem. For the offline algorithm, we formulate data center management as a cost minimization problem by considering energy cost, delay cost (to measure service quality), and switching cost (to change servers’s active/idle mode). Then, we analyze certain properties of an optimal solution which lead to a dynamic programming based algorithm. Moreover, by revising the solution procedure, we successfully eliminate the recursive procedure and achieve an optimal offline algorithm with a polynomial complexity. For the online algorithm, We design it by considering the worst case scenario for future workload. In simulation, we show this online algorithm can always provide near-optimal solutions. [ABSTRACT FROM PUBLISHER]

Efficient and effective system-level power management for multi-core systems with multiple voltage islands is necessary for next-generation computing systems. This paper considers energy efficiency for such systems, in which the cores in the same voltage island have to be operated at the same supply voltage level. We explore how to map given task sets onto cores, so that each task set is assigned and executed on one core and the energy consumption is minimized. Due to the restriction to operate at the same supply voltage in a voltage island, different mappings will result in different energy consumptions. By using the simple single frequency approximation scheme (SFA) to decide the voltages and frequencies of individual voltage islands, this paper presents the approximation factor analysis (in terms of energy consumption) for simple heuristic algorithms, and develops a dynamic programming algorithm, which derives optimal mapping solutions for energy minimization when using SFA. We experimentally evaluate the running time and energy consumption performance of these algorithms on Intel’s single-chip cloud computer (SCC). Moreover, we conduct simulations for hypothetical platforms with different number of voltage islands and cores per island, also considering different task partitioning policies. [ABSTRACT FROM PUBLISHER]

Energy efficiency along with enhanced performance are two important goals of scheduling on multiprocessors. This paper proposes a Contention-aware, Energy Effïcient, Duplication based Mixed Integer Programming (CEEDMIP) formulation for scheduling task graphs on heterogeneous multiprocessors, interconnected in a distributed system or a network on chip architecture. The effect of duplication is studied with respect to minimizing: the makespan, the total energy for processing tasks and messages on processors and network resources respectively and the tardiness of tasks with respect to their deadlines. Optimizing the use of duplication with MIP provides both energy effïciency and performance by reducing the communication energy consumption and the communication latency. The contention awareness gives a more accurate estimation of the energy consumption. We also propose a corner case that allows the scheduling of a parent task copy after a copy of the child task which may lead to efficient schedules. It has been observed that the proposed MIP with a clustering based heuristic provides scalability and gives 10-30 percent improvement in energy with improved makespan and accuracy when compared with other duplication based energy aware algorithms. [ABSTRACT FROM AUTHOR]

As datacenters grow in scale, increasing energy costs and carbon emissions have led data centers to seek renewable energy, such as wind and solar energy. However, tackling the challenges associated with the intermittency and variability of renewable energy is difficult. This paper proposes a scheme called GreenMatch, which deploys an SSD cache to match green energy supplies with a time-shifting workload schedule while maintaining low latency for online data-intensive services. With the SSD cache, the process for a latency-sensitive request to access a disk is divided into two stages: a low-energy/low-latency online stage and a high-energy/high-latency off-line stage. As the process in the latter stage is off-line, it offers opportunities for time-shifting workload scheduling in response to variations of green energy supplies. We also allocate an HDD cache to guarantee data availability when renewable energy is inadequate. Furthermore, we design a novel replacement policy called Inactive P-disk First for the HDD cache to avoid inactive disk accesses. The experimental results show that GreenMatch can make full use of renewable energy while minimizing the negative impacts of intermittency and variability on performance and availability. [ABSTRACT FROM AUTHOR]

Energy consumed by Cloud datacenters has dramatically increased, driven by rapid uptake of applications and services globally provisioned through virtualization. By applying energy-aware virtual machine scheduling, Cloud providers are able to achieve enhanced energy efficiency and reduced operation cost. Energy consumption of datacenters consists of computing energy and cooling energy. However, due to the complexity of energy and thermal modeling of realistic Cloud datacenter operation, traditional approaches are unable to provide a comprehensive in-depth solution for virtual machine scheduling which encompasses both computing and cooling energy. This paper addresses this challenge by presenting an elaborate thermal model that analyzes the temperature distribution of airflow and server CPU. We propose GRANITE – a holistic virtual machine scheduling algorithm capable of minimizing total datacenter energy consumption. The algorithm is evaluated against other existing workload scheduling algorithms MaxUtil, TASA, IQR and Random using real Cloud workload characteristics extracted from Google datacenter tracelog. Results demonstrate that GRANITE consumes 4.3—43.6 percent less total energy in comparison to the state-of-the-art, and reduces the probability of critical temperature violation by 99.2 with 0.17 percent SLA violation rate as the performance penalty. [ABSTRACT FROM AUTHOR]

As cloud computing services have gained popularity, users view videos on websites (e.g., YouTube) to generate high CPU resource utilization and bandwidth for video streaming data centers. However, popular videos result in power-law features to cause imbalanced resource utilization. In addition, hotspot and idle servers generate extra power consumption in data centers. Previous studies considered to satisfy the requirements of users, provide faster access rates and save power consumption. However, fewer studies considered resource utilization with different popularity videos. Therefore, this paper proposes an energy efficient virtual machine (VM) management scheme with power-law features (VMPL). VMPL predicts the resource utilization of the video in the future based on the popularity, ensures enough resources for upcoming videos, and turns off idle servers for power saving. Simulation results validated by mathematical analysis show that VMPL has the best resource utilization and the lowest power consumption compared with Nash and Best-Fit algorithms. [ABSTRACT FROM AUTHOR]

High-performance computing systems are moving towards 2.5D and 3D memory hierarchies, based on High Bandwidth Memory (HBM) and Hybrid Memory Cube (HMC) to mitigate the main memory bottlenecks. This trend is also creating new opportunities to revisit near-memory computation. In this paper, we propose a flexible processor-in-memory (PIM) solution for scalable and energy-efficient execution of deep convolutional networks (ConvNets), one of the fastest-growing workloads for servers and high-end embedded systems. Our co-design approach consists of a network of Smart Memory Cubes (modular extensions to the standard HMC) each augmented with a many-core PIM platform called NeuroCluster. NeuroClusters have a modular design based on NeuroStream coprocessors (for Convolution-intensive computations) and general-purpose RISC-V cores. In addition, a DRAM-friendly tiling mechanism and a scalable computation paradigm are presented to efficiently harness this computational capability with a very low programming effort. NeuroCluster occupies only 8 percent of the total logic-base (LoB) die area in a standard HMC and achieves an average performance of 240 GFLOPS for complete execution of full-featured state-of-the-art (SoA) ConvNets within a power budget of 2.5 W. Overall 11 W is consumed in a single SMC device, with 22.5 GFLOPS/W energy-efficiency which is 3.5X better than the best GPU implementations in similar technologies. The minor increase in system-level power and the negligible area increase make our PIM system a cost-effective and energy efficient solution, easily scalable to 955 GFLOPS with a small network of just four SMCs. [ABSTRACT FROM AUTHOR]

Previous work on optimizing resource provisioning in virtualized environments focused either on mapping virtual machines (VMs) to physical machines (PMs) or mapping application components to VMs. In this paper, we argue that these two optimization problems influence each other significantly and in a highly non-trivial way. We define a sophisticated problem formulation for the joint optimization of the two mappings, taking into account sizing aspects, colocation constraints, license costs, and hardware affinity relations. As demonstrated by the empirical evaluation on a real-world workload trace, the combined optimization leads to significantly better overall results than considering the two problems in isolation. [ABSTRACT FROM PUBLISHER]

For chip multiprocessor systems (CMPs), the interference on shared resources such as on-chip caches typically leads to unbalanced progress among threads. Because of the inherent synchronization primitives, such as barriers and locks, cores running fast threads have to waste precious cycles to wait for cores with slow progress, which leads to performance and energy inefficiency. For the purpose of improving performance and reducing energy consumption, this paper proposes to adapt the cache coherence policy for threads according to their delay-tolerant levels. Specifically, this paper proposes Thread progrEss Aware Coherence Adaption (TEACA) which utilizes the thread progress information as hints for coherence adaption. TEACA dynamically utilize the memory system statistics to estimate the progress of threads. Based on the estimated thread progress information, TEACA categorizes threads into leader threads and laggard threads. The thread categorization decisions are then leveraged for efficient coherence adaption on CMP systems supporting hybrid coherence protocols. Experimental results show that, on a 64-core CMP system, TEACA outperforms directory protocol in application execution time and a recently proposed hybrid protocol in both application execution time and energy dissipation. [ABSTRACT FROM AUTHOR]

Mobile applications are becoming increasingly feature-rich and powerful, but also dependent on large main memories, which consume a large portion of system energy, especially for devices equipped with 4/6 GB DRAM. Swapping inactive DRAM pages to byte-addressable, non-volatile memory (NVRAM) is a promising solution to this problem. However, most NVRAMs have limited write endurance and the current victim pages selecting algorithm does not aware it. Therefore, to make it practical, the design of an NVRAM based swapping system must also consider endurance. In this paper, we target at prolonging the lifetime of NVRAM based swap area in mobile devices by reducing the write activities to NVRAM based swap area. Different from traditional wisdom, such as wear leveling and hot/cold data identification, we propose to build a system called nCode, which exploits the fact that code pages are easy to identify, read-only, and therefore a perfect candidate for swapping. Utilizing NVRAM’s byte-addressability, we support execute-in-place (XIP) of the code pages in the swap area, without copying them back to DRAM based main memory. Experimental results based on the Google Nexus 5 smartphone show that nCode can effectively prolong the lifetime of NVRAM under various workloads. [ABSTRACT FROM PUBLISHER]

The end of Dennard's scaling poses computer systems, especially the datacenters, in front of both power and utilization walls. One possible solution to combat the power and utilization walls is dark silicon where transistors are under-utilized in the chip, but this will result in a diminishing performance. Another solution is Near-Threshold Voltage Computing (NTC) which operates transistors in the near-threshold region and provides much more flexible tradeoffs between power and performance. However, prior efforts largely focus on a specific design option based on the legacy desktop applications, therefore, lacking comprehensive analysis of emerging scale-out applications with multiple design options when dark silicon and/or NTC are/is applied. In this paper, we characterize different perspectives including performance, energy efficiency and reliability in the context of NTC/dark silicon cloud processors running emerging scale-out workloads on various architecture designs. We find NTC is generally an effective way to alleviate the power challenge over scale-out applications compared with dark silicon, it can improve performance by 1.6X, energy efficiency by 50 percent and the reliability problem can be relieved by ECC. Meanwhile, we also observe tiled-OoO architecture improves the performance by 20∼370 percent and energy efficiency by 40 ∼ 600 percent over alternative architecture designs, making it a preferable design paradigm for scale-out workloads. We believe that our observations will provide insights for the design of cloud processors under dark silicon and/or NTC . [ABSTRACT FROM AUTHOR]

In cloud computing, with full control of the underlying infrastructures, cloud providers can flexibly place user jobs on suitable physical servers and dynamically allocate computing resources to user jobs in the form of virtual machines. As a cloud provider, scheduling user jobs in a way that minimizes their completion time is important, as this can increase the utilization, productivity, or profit of a cloud. In this paper, we focus on the problem of scheduling embarrassingly parallel jobs composed of a set of independent tasks and consider energy consumption during scheduling. Our goal is to determine task placement plan and resource allocation plan for such jobs in a way that minimizes the Job Completion Time (JCT). We begin with proposing an analytical solution to the problem of optimal resource allocation with pre-determined task placement. In the following, we formulate the problem of scheduling a single job as a Non-linear Mixed Integer Programming problem and present a relaxation with an equivalent Linear Programming problem. We further propose an algorithm named TaPRA and its simplified version TaPRA-fast that solve the single job scheduling problem. Lastly, to address multiple jobs in online scheduling, we propose an online scheduler named OnTaPRA. By comparing with the start-of-the-art algorithms and schedulers via simulations, we demonstrate that TaPRA and TaPRA-fast reduce the JCT by 40-430 percent and the OnTaPRA scheduler reduces the average JCT by 60-280 percent. In addition, TaPRA-fast can be 10 times faster than TaPRA with around 5 percent performance degradation compared to TaPRA, which makes the use of TaPRA-fast very appropriate in practice. [ABSTRACT FROM AUTHOR]

A smart community is a distributed system consisting of a set of smart homes which utilize the smart home scheduling techniques to enable customers to automatically schedule their energy loads targeting various purposes such as electricity bill reduction. Smart home scheduling is usually implemented in a decentralized fashion inside a smart community, where customers compete for the community level renewable energy due to their relatively low prices. Typically there exists an aggregator as a community wide electricity policy maker aiming to minimize the total electricity bill among all customers. This paper develops a new renewable energy aware pricing scheme to achieve this target. We establish the proof that under certain assumptions the optimal solution of decentralized smart home scheduling is equivalent to that of the centralized technique, reaching the theoretical lower bound of the community wide total electricity bill. In addition, an advanced cross entropy optimization technique is proposed to compute the pricing scheme of renewable energy, which is then integrated in smart home scheduling. The simulation results demonstrate that our pricing scheme facilitates the reduction of both the community wide electricity bill and individual electricity bills compared to the uniform pricing. In particular, the community wide electricity bill can be reduced to only 0.06 percent above the theoretic lower bound. [ABSTRACT FROM AUTHOR]

With the increased complexity of platforms coupled with data centers' servers sprawl, power consumption is reaching unsustainable limits. Researchers have addressed data centers' performance-per-watt management at different hierarchies going from server clusters to servers to individual components within the server platform. This paper addresses performance-per-watt maximization of memory subsystems in a data center. Traditional memory power management techniques rely on profiling the utilization of memory modules and transitioning them to some low-power mode when they are sufficiently idle. However, fully interleaved memory presents an interesting research challenge because data striping across memory modules reduces the idleness of individual modules to warrant transitions to low-power states. In this paper, we present a novel technique for performance-per-watt maximization of interleaved memory by dynamically reconfiguring (expanding or contracting) the degree of interleaving to adapt to incoming workload. The reconfigured memory hosts the application's working set on a smaller set of modules in a manner that exploits the platform's memory hierarchy architecture. This creates the opportunity for the remaining memory modules to transition to low-power states and remain in those states for as long as the performance remains within given acceptable thresholds. The memory power expenditure is minimized subject to application memory requirements and end-to-end memory access delay constraints. This is formulated as a performance-per- watt maximization problem and solved using an analytical memory power and performance model. Our technique has been validated on a real server using SPECjbb benchmark and on a trace-driven memory simulator using SPECjbb and gcc memory traces. On the server, our techniques are shown to give about 48.8 percent (26.7 kJ) energy savings compared to traditional techniques measured at 4.5 percent. The maximum improvement in performance-per-watt was measured at 88.48 percent. The simulator showed 89.7 percent improvement in performance-per-watt compared to thebest performing traditional technique. [ABSTRACT FROM AUTHOR]

The three-dimensional Network-on-Chips (3D NoCs) has become a mature multi-core interconnection architecture in recent years. However, the traditional electrical lines have very limited bandwidth and high energy consumption, making the photonic interconnection promising for future 3D Optical NoCs (ONoCs). Since existing solutions cannot well guarantee the fault-tolerant ability of 3D ONoCs, in this paper, we propose a reliable optical router (OR) structure which sacrifices less redundancy to obtain more restore paths. Moreover, by using our fault-tolerant routing algorithm, the restore path can be found inside the disabled OR under the deadlock-free condition, i.e., fault-node reuse. Experimental results show that the proposed approach outperforms the previous related works by maximum 81.1 percent and 33.0 percent on average for throughput performance under different synthetic and real traffic patterns. It can improve the system average optical signal to noise ratio (OSNR) performance by maximum 26.92 percent and 12.57 percent on average, and it can improve the average energy consumption performance by 0.3 percent to 15.2 percent under different topology types/sizes, failure rates, OR structures, and payload packet sizes. [ABSTRACT FROM AUTHOR]

The adoption of large-scale MPSoCs and the globalization of the IC design flow give rise to two major concerns: high power density due to continuous technology scaling and security due to the untrustworthiness of the third-party intellectual property (3PIP) cores. However, little work has been undertaken to consider these two critical issues jointly during the design stage. In this paper, we propose a design methodology that minimizes the energy consumption while simultaneously protecting the MPSoC against the effects of hardware trojans. The proposed methodology consists of three main stages: 1) Task scheduling to introduce core diversity in the MPSoC in order to detect the presence of malicious modifications in the cores, or mute their effects at runtime, 2) Vendor assignment to the cores using a novel heuristic that chooses vendor-specific cores with operating speed that minimizes the total energy consumption of the MPSoC, and 3) Explore optimization opportunities for further energy savings by minimizing idle periods on the cores, which are caused by the inter-task data dependencies. Experimental results show that our solutions consume only 1/3 energy of existing solutions without increasing schedule length while satisfying the security constraints. [ABSTRACT FROM AUTHOR]

The concept of the industrial Internet of things (IIoT) is being widely applied to service provisioning in many domains, including smart healthcare, intelligent transportation, autopilot, and the smart grid. However, because of the IIoT devices’ limited onboard resources, supporting resource-intensive applications, such as 3D sensing, navigation, AI processing, and big-data analytics, remains a challenging task. In this paper, we study the multi-hop computation-offloading problem for the IIoT–edge–cloud computing model and adopt a game-theoretic approach to achieving Quality of service (QoS)-aware computation offloading in a distributed manner. First, we study the computation-offloading and communication-routing problems with the goal of minimizing each task's computation time and energy consumption, formulating the joint problem as a potential game in which the IIoT devices determine their computation-offloading strategies. Second, we apply a free–bound mechanism that can ensure a finite improvement path to a Nash equilibrium. Third, we propose a multi-hop cooperative-messaging mechanism and develop two QoS-aware distributed algorithms that can achieve the Nash equilibrium. Our simulation results show that our algorithms offer a stable performance gain for IIoT in various scenarios and scale well as the device size increases. [ABSTRACT FROM AUTHOR]

Sensor networks have emerged as a promising technology with various applications, where power efficiency is one of the critical requirements. The recent IEEE 802.15.4 standard offers a promising platform for wireless sensor networks. Since each node can act as a coordinator or a device in the IEEE 802.15.4 standard, 802.15.4-based sensor networks have various possible network topologies. To reduce power consumption, in this paper, we try to construct network topologies with a small number of coordinators while still maintaining network connectivity. By reducing the number of coordinators, the average duty cycle is reduced and the battery life is prolonged. Three topology control algorithms are proposed in this paper. Self-pruning (SP) is the simplest one with O(1) running time and provides the shortest path to the sink node. Ordinal pruning (OP) can significantly improve SP in terms of power saving with O(n) running time. Layered pruning (LP) is a trade off between the first two pruning algorithms with O(√n) running time and has a slightly higher power consumption than OP. Furthermore, all three algorithms are independent of the physical radio propagation characteristics. Extensive simulations have been performed to verify the effectiveness of the proposed topology control schemes. [ABSTRACT FROM AUTHOR]

This paper proposes an N-modular redundancy (NMR) technique with low energy-overhead for hard real-time multi-core systems. NMR is well-suited for multi-core platforms as they provide multiple processing units and low-overhead communication for voting. However, it can impose considerable energy overhead and hence its energy overhead must be controlled, which is the primary consideration of this paper. For this purpose the system operation can be divided into two phases: indispensable phase and on-demand phase. In the indispensable phase only half-plus-one copies for each task are executed. When no fault occurs during this phase, the results must be identical and hence the remaining copies are not required. Otherwise, the remaining copies must be executed in the on-demand phase to perform a complete majority voting. In this paper, for such a two-phase NMR, an energy-management technique is developed where two new concepts have been considered: i) Block-partitioned scheduling that enables parallel task execution during on-demand phase, thereby leaving more slack for energy saving, ii) Pseudo-dynamic slack, that results when a task has no faulty execution during the indispensable phase and hence the time which is reserved for its copies in the on-demand phase is reclaimed for energy saving. The energy-management technique has an off-line part that manages static and pseudo-dynamic slacks at design time and an online part that mainly manages dynamic slacks at run-time. Experimental results show that the proposed NMR technique provides up to 29 percent energy saving and is 6 orders of magnitude higher reliable as compared to a recent previous work. [ABSTRACT FROM PUBLISHER]

This paper first presents an analysis strategy to meet requirements of a sensing application through trade-offs between the energy consumption (lifetime) and source-to-sink transport delay under reliability constraint wireless sensor networks. A novel data gathering protocol named Broadcasting Combined with Multi-NACK/ACK (BCMN/A) protocol is proposed based on the analysis strategy. The BCMN/A protocol achieves energy and delay efficiency during the data gathering process both in intra-cluster and inter-cluster. In intra-cluster, after each round of TDMA collection, a cluster head broadcasts NACK to indicate nodes which fail to send data in order to prevent nodes that successfully send data from retransmission. The energy for data gathering in intra-cluster is conserved and transport delay is decreased with multi-NACK mechanism. Meanwhile in inter-clusters, multi-ACK is returned whenever a sensor node sends any data packet. Although the number of ACKs to be sent is increased, the number of data packets to be retransmitted is significantly decreased so that consequently it reduces the node energy consumption. The BCMN/A protocol is evaluated by theoretical analysis as well as extensive simulations and these results demonstrate that our proposed protocol jointly optimizes the network lifetime and transport delay under network reliability constraint. [ABSTRACT FROM AUTHOR]

In this paper we study energy conservation in the Internet. We observe that different traffic volumes on a link can result in different energy consumption; this is mainly due to such technologies as trunking (IEEE 802.1AX), adaptive link rates, etc. We design a green Internet routing scheme, where the routing can lead traffic in a way that is green. We differ from previous studies where they switch network components, such as line cards and routers, into sleep mode. We do not prune the Internet topology. We first develop a power model, and validate it using real commercial routers. Instead of developing a centralized optimization algorithm, which requires additional protocols such as MPLS to materialize in the Internet, we choose a hop-by-hop approach. It is thus much easier to integrate our scheme into the current Internet. We progressively develop three algorithms, which are loop-free, substantially reduce energy consumption, and jointly consider green and QoS requirements such as path stretch. We further analyze the power saving ratio, the routing dynamics, and the relationship between hop-by-hop green routing and QoS requirements. We comprehensively evaluate our algorithms through simulations on synthetic, measured, and real topologies, with synthetic and real traffic traces. We show that the power saving in the line cards can be as much as 50 percent. [ABSTRACT FROM AUTHOR]

Demand-side management, together with the integration of distributed energy storage have an essential role in the process of improving the efficiency and reliability of the power grid. In this paper, we consider a smart power system in which users are equipped with energy storage devices. Users will request their energy demands from an energy provider who determines their energy payments based on the load profiles of users. By scheduling the energy consumption and storage of users regulated by a central controller, the energy provider tries to minimize the square euclidean distance between the instantaneous energy demand and the average demand of the power system. The users intend to reduce their energy payment by jointly scheduling their appliances and controlling the charging and discharging process for their energy storage devices. We apply game theory to formulate the energy consumption and storage game for the distributed design, in which the players are the users and their strategies are the energy consumption schedules for appliances and storage devices. Based on the game theory setup and proximal decomposition, we also propose two distributed demand side management algorithms executed by users in which each user tries to minimize its energy payment, while still preserving the privacy of users as well as minimizing the amount of required signaling with the central controller. In simulation results, we show that the proposed algorithms provide optimality for both energy provider and users. [ABSTRACT FROM AUTHOR]

Recently, intelligent scheduling approaches using surrogate models have been proposed to efficiently allocate volatile tasks in heterogeneous fog environments. Advances like deterministic surrogate models, deep neural networks (DNN) and gradient-based optimization allow low energy consumption and response times to be reached. However, deterministic surrogate models, which estimate objective values for optimization, do not consider the uncertainties in the distribution of the Quality of Service (QoS) objective function that can lead to high Service Level Agreement (SLA) violation rates. Moreover, the brittle nature of DNN training and the limited exploration with low agility in gradient-based optimization prevent such models from reaching minimal energy or response times. To overcome these difficulties, we present a novel scheduler that we call GOSH for Gradient Based Optimization using Second Order derivatives and Heteroscedastic Deep Surrogate Models. GOSH uses a second-order gradient based optimization approach to obtain better QoS and reduce the number of iterations to converge to a scheduling decision, subsequently lowering the scheduling time. Instead of a vanilla DNN, GOSH uses a Natural Parameter Network (NPN) to approximate objective scores. Further, a Lower Confidence Bound (LCB) optimization approach allows GOSH to find an optimal trade-off between greedy minimization of the mean latency and uncertainty reduction by employing error-based exploration. Thus, GOSH and its co-simulation based extension GOSH*, can adapt quickly and reach better objective scores than baseline methods. We show that GOSH* reaches better objective scores than GOSH, but it is suitable only for high resource availability settings, whereas GOSH is apt for limited resource settings. Real system experiments for both GOSH and GOSH* show significant improvements against the state-of-the-art in terms of energy consumption, response time and SLA violations by up to 18, 27 and 82 percent, respectively. [ABSTRACT FROM AUTHOR]

The emerging hybrid DRAM-NVM architecture is challenging the existing memory management mechanism at the level of the architecture and operating system. In this paper, we introduce Memos, a memory management framework which can hierarchically schedule memory resources over the entire memory hierarchy including cache, channels, and main memory comprising DRAM and NVM simultaneously. Powered by our newly designed kernel-level monitoring module that samples the memory patterns by combining TLB monitoring with page walks, and page migration engine, Memos can dynamically optimize the data placement in the memory hierarchy in response to the memory access pattern, current resource utilization, and memory medium features. Our experimental results show that Memos can achieve high memory utilization, improving system throughput by around 20.0 percent; reduce the memory energy consumption by up to 82.5 percent; and improve the NVM lifetime by up to 34X. [ABSTRACT FROM AUTHOR]

Application partitioning that splits the executions into local and remote parts, plays a critical role in high-performance mobile offloading systems. Optimal partitioning will allow mobile devices to obtain the highest benefit from Mobile Cloud Computing (MCC) or Mobile Edge Computing (MEC). Due to unstable resources in the wireless network (network disconnection, bandwidth fluctuation, network latency, etc.) and at the service nodes (different speeds of mobile devices and cloud/edge servers, memory, etc.), static partitioning solutions with fixed bandwidth and speed assumptions are unsuitable for offloading systems. In this paper, we study how to dynamically partition a given application effectively into local and remote parts while reducing the total cost to the degree possible. For general tasks (represented in arbitrary topological consumption graphs), we propose a Min-Cost Offloading Partitioning (MCOP) algorithm that aims at finding the optimal partitioning plan (i.e., to determine which portions of the application must run on the mobile device and which portions on cloud/edge servers) under different cost models and mobile environments. Simulation results show that the MCOP algorithm provides a stable method with low time complexity which significantly reduces execution time and energy consumption by optimally distributing tasks between mobile devices and servers, besides it adapts well to mobile environmental changes. [ABSTRACT FROM AUTHOR]

Storage subsystem is considered as the performance bottleneck of computer systems in data-intensive applications. Solid-State Drives (SSDs) are emerging storage devices which unlike Hard Disk Drives (HDDs), do not have mechanical parts and therefore, have superior performance compared to HDDs. Due to the high cost of SSDs, entirely replacing HDDs with SSDs is not economically justified. Additionally, SSDs can endure a limited number of writes before failing. To mitigate the shortcomings of SSDs while taking advantage of their high performance, SSD caching is practiced in both academia and industry. Previously proposed caching architectures have only focused on either performance or endurance and neglected to address both parameters in suggested architectures. Moreover, the cost, reliability, and power consumption of such architectures is not evaluated. This paper proposes a hybrid I/O caching architecture that while offers higher performance than previous studies, it also improves power consumption with a similar budget. The proposed architecture uses DRAM, Read-Optimized SSD (RO-SSD), and Write-Optimized SSD (WO-SSD) in a three-level cache hierarchy and tries to efficiently redirect read requests to either DRAM or RO-SSD while sending writes to WO-SSD. To provide high reliability, dirty pages are written to at least two devices which removes any single point of failure. The power consumption is also managed by reducing the number of accesses issued to SSDs. The proposed architecture reconfigures itself between performance- and endurance-optimized policies based on the workload characteristics to maintain an effective tradeoff between performance and endurance. We have implemented the proposed architecture on a server equipped with industrial SSDs and HDDs. The experimental results show that as compared to state-of-the-art studies, the proposed architecture improves performance and power consumption by an average of 8 and 28 percent, respectively, and reduces the cost by 5 percent while increasing the endurance cost by 4.7 percent and negligible reliability penalty. [ABSTRACT FROM AUTHOR]

Hadoop, especially Hadoop 2.0, has been a dominant framework for real-time big data processing. However, Hadoop is not optimized for energy efficiency. Aiming to solve this problem, in this paper, we propose a new framework to improve the energy efficiency of Hadoop 2.0. We focus on the resource manager in Hadoop 2.0, namely YARN, and propose energy-efficient task scheduling mechanisms on YARN. Particularly, we focus on CPU-intensive streaming jobs and classify streaming jobs into two types, namely batch streaming jobs (i.e., a set of jobs are submitted simultaneously) and online streaming jobs (i.e., jobs are continuously submitted one by one). We devise different energy-efficient task scheduling algorithms for each kind of streaming jobs. Specially, we first propose to abstractly model performance and energy consumption by considering the characteristics of tasks as well as the computational resources in YARN. Based on this model, we study the energy efficiency of streaming tasks which consist of the performance model and energy consumption model of task. We propose two key principles for improving energy efficiency: 1) CPU usage aware task allocation, partitions tasks to NMs based on the task characteristic in term of CPU usage; and 2) resource efficient task allocation, reduce idle resource. Then, we propose a D-based binning algorithm for the batch task scheduling and K-based binning algorithm for the online task scheduling that can adapt to continuously arriving tasks. We conduct extensive experiments on a real Hadoop 2.0 cluster and use two kinds of workloads to evaluate the performance and energy efficiency of our proposal. Compared with Storm (the streaming data processing tool in Hadoop 2.0) and other approaches including TAPA and DVFS-MR, our proposal is more energy efficient. The batch task scheduling algorithm reduces up to 10 percent of energy consumption and keeps comparable performance. In addition, the online task scheduling algorithm reduces up to 7 percent over the existing algorithms. [ABSTRACT FROM AUTHOR]

Multi-installment scheduling (MIS) has been deemed as a promising paradigm that can sharply reduce the processing time of large-scale divisible workloads on various network-based compute platforms. Unfortunately, the practicality of MIS was crippled due to its overwhelming complexity for deriving optimal values for $(n\times m)+2$(n×m)+2 related variables, i.e., we have to obtain an optimal number $n$n of required computing resources, optimal number $m$m of installments, and optimal load partition matrix $A=(\alpha _{ij})_{n\times m}$A=(αij)n×m which determines the sizes of load fractions assigned to each computing unit in every installment. To circumvent this complexity, in this paper, we first derive explicit analytical expressions for optimal load partition matrix $A$A of size $n\times m$n×m based on a given number of $n$n and $m$m. Then we propose a heuristic algorithm referred to as Time, Resource, and Energy Efficient MIS (TREE-MIS) to determine optimal values of $n$n and $m$m. The efficiency of our approach is shown to significantly improve since it can produce globally optimal solutions directly for $(n\times m)$(n×m) variables among $(n\times m)+2$(n×m)+2 in total for MIS problems based on the derived analytical expressions within a short runtime. We conduct extensive simulations to demonstrate the effectiveness of the proposed algorithm. Simulation results show that our TREE-MIS can not only minimize the processing time of workloads as well as improve resource utilization of the compute platform but also drastically reduce the runtime compared to other state-of-art MIS strategies. Furthermore, while handling large-scale workloads in any large network infrastructures would inexorably result in significant amounts of energy wastage if the strategy is not prudently designed. As an offshoot of our analysis and design, we clearly demonstrate that the energy wastage in adopting our TREE-MIS is kept minimum when compared to other currently available strategies in practice. [ABSTRACT FROM AUTHOR]

Hardware energy efficiency has been one of the prominent objectives of system design in the last two decades. However, with the recent explosion in mobile computing and the increasing demand for green data centers, software energy efficiency has also risen to be an equally important factor. The majority of classic concurrency control algorithms were designed in an era when energy efficiency was not an important dimension in algorithm design. Concurrency control algorithms are applied to solve a wide range of problems from kernel-level primitives in operating systems to networking devices and web services. These primitives and services are constantly and heavily invoked in any computing system and by a larger scale in networking devices and data centers. Thus, even a small change in their energy spectrum can make a huge impact on overall energy consumption for long periods of time. This paper focuses on the classic producer-consumer problem. First, we study the energy profile of a set of existing producer-consumer algorithms. In particular, we present evidence that although these algorithms share the same functional goals, their behavior with respect to energy consumption are drastically different. Then, we present a dynamic algorithm for the multiple producer-consumer problem, where consumers in a multicore system use learning mechanisms to predict the rate of production, and effectively utilize this prediction to attempt to latch onto previously scheduled CPU wake-ups. Such group latching increases the idle time between consumer activations resulting in more CPU idle time and, hence, lower average CPU frequency. This in turn reduces energy consumption. We enable consumers to dynamically reserve more pre-allocated memory in cases where the production rate is too high. Consumers may compete for the extra space and dynamically release it when it is no longer needed. Our experiments show that our algorithm provides a 38 percent decrease in energy consumption compared to a mainstream semaphore-based producer-consumer implementation when running 10 parallel consumers. We validate the effectiveness of our algorithm with a set of thorough experiments on varying parameters of scalability. Finally, we present our recommendations on when our algorithm is most beneficial. [ABSTRACT FROM AUTHOR]

Fiber-Wireless (FiWi) network is a classification of network that combines the massive bandwidth of the optical network and the reach of the wireless network. FiWi networks are usually composed of an optical and a wireless component. Since both components are designed to work independently, some mechanisms, such as the different power saving methods in both components, may not cooperate with each other and this may result in an undesirable performance. In this paper, we identify that the conflicting power saving mechanisms cause unnecessary energy consumption and introduce additional delay to the overall FiWi network. To cope with this problem, we propose a novel ONU sleep method, which dynamically control the ONU sleep period based on the STAs energy control mechanism. Finally, we demonstrate that our proposed method has shorter latency and is more efficient in term of energy consumption than the existing method. [ABSTRACT FROM AUTHOR]

NUCA caches have traditionally been proposed as a solution for mitigating wire delays, and delays introduced due to complex networks on chip. Traditional approaches have reported significant performance gains with intelligent block placement, location, replication, and migration schemes. In this paper, we propose a novel approach in this space, called FP-NUCA. It differs from conventional approaches, and relies on a novel method of co-designing the last level cache and the network on chip. We artificially constrain the communication pattern in the NUCA cache such that all the messages travel along a few predefined paths (fast paths) for each set of banks. We leverage this communication pattern by designing a new type of NOC router called the Freeze router, which augments a regular router by adding a layer of circuitry that gates the clock of the regular router when there is a fast path message waiting to be transmitted. Messages along the fast path do not require buffering, switching, or routing. We incorporate a bank predictor with our novel NOC for reducing the number of messages, and resultant energy consumption. We compare our performance with state of the art protocols, and report speedups of up to 31 percent (mean: 6.3 percent), and $ED^2$ reduction up to 46 percent (mean: 10.4 percent) for a suite of Splash and Parsec benchmarks. We implement the Freeze router in VHDL and show that the additional fast path logic has minimal area and timing overheads. [ABSTRACT FROM AUTHOR]

The past decade witnessed the tremendous growth of online services and applications. Together with the increase of cloud computing, more and more computation are hosted by Internet data centers (IDCs). Today’s IDCs are achieving significant advances in communication and computation capabilities. However, along with the increasing demand from IDC clients, power consumption for powering up and cooling these IDCs has been skyrocketing. Most existing works optimize the power consumption of either servers or Computer Room Air Conditioners (CRACs), and overlook the correlation between the power consumption of these two types of equipment. In this paper, we propose an adaptive power control method which leverages the correlation between the power consumption of servers and CRACs. To capture the workload uncertainties and thermal dynamics, we exploit Recursive-Least Square based Model Predictive Control (MPC) to solve the power control problem. Performance evaluations shows the effective power peak reduction using our approach. [ABSTRACT FROM AUTHOR]

Coverage of interest points and network connectivity are two main challenging and practically important issues of Wireless Sensor Networks (WSNs). Although many studies have exploited the mobility of sensors to improve the quality of coverage andconnectivity, little attention has been paid to the minimization of sensors’ movement, which often consumes the majority of the limited energy of sensors and thus shortens the network lifetime significantly. To fill in this gap, this paper addresses the challenges of the Mobile Sensor Deployment (MSD) problem and investigates how to deploy mobile sensors with minimum movement to form a WSN that provides both target coverage and network connectivity. To this end, the MSD problem is decomposed into two sub-problems: the Target COVerage (TCOV) problem and the Network CONnectivity (NCON) problem. We then solve TCOV and NCON one by one and combine their solutions to address the MSD problem. The NP-hardness of TCOV is proved. For a special case of TCOV where targets disperse from each other farther than double of the coverage radius, an exact algorithm based on the Hungarian method is proposed to find the optimal solution. For general cases of TCOV, two heuristic algorithms, i.e., the Basic algorithm based on clique partition and the TV-Greedy algorithm based on Voronoi partition of the deployment region, are proposed to reduce the total movement distance ofsensors. For NCON, an efficient solution based on the Steiner minimum tree with constrained edge length is proposed. Thecombination of the solutions to TCOV and NCON, as demonstrated by extensive simulation experiments, offers a promising solutionto the original MSD problem that balances the load of different sensors and prolongs the network lifetime consequently. [ABSTRACT FROM AUTHOR]

WiFi and cellular networks are pervasively provided for mobile Internet access. Although most existing mobile devices are equipped with both WiFi and cellular network interfaces, concurrent data transmissions over these interfaces for improved throughput are not provided. In this paper, a bandwidth aggregation prototype, named Application Layer Protocol based Aggregation (ALP-A), is developed for easy use by simply installing an application in mobile devices without modifying their operating systems or drivers. It provides desired quality-of-experience (QoE), i.e., acceptable response delay to users, learned from application characteristics and users behaviors. Furthermore, we propose an online algorithm of traffic scheduling over WiFi and cellular interfaces with the objective of minimizing energy consumption while guaranteeing the QoE. Over the prototype implemented on Andriod-based smartphones, we conduct extensive experiments to show that ALP-A outperforms existing schemes significantly. [ABSTRACT FROM PUBLISHER]

Lately, for geo-distributed data centers, a workload management approach that routes user requests to locations with cheaper and cleaner electricity has been developed to reduce energy consumption and cost. We consider two key aspects that have not been explored in this approach. First, through empirical studies, we find that the energy efficiency of cooling systems depends critically on the ambient temperature, which exhibits significant geographical diversity. Temperature diversity can be used to reduce the cooling energy overhead. Second, energy consumption comes from not only interactive workloads driven by user requests, but also delay tolerant batch workloads that run at the back-end. The elastic nature of batch workloads can be exploited to further reduce the energy cost. In this paper, we propose to make workload management temperature aware. We formulate the problem as a joint optimization of request routing for interactive workloads and capacity allocation for batch workloads. We develop a distributed algorithm based on an $m$ -block alternating direction method of multipliers (ADMM) algorithm that extends the classical two-block algorithm. We prove the convergence and rate of convergence results under general assumptions. Through trace-driven simulations, we find that our approach consistently provides 15-20 percent cooling energy reduction, and 5-20 percent overall cost reduction over existing methods. [ABSTRACT FROM PUBLISHER]

Trust models have been recently suggested as an effective security mechanism for Wireless Sensor Networks (WSNs). Considerable research has been done on modeling trust. However, most current research work only takes communication behavior into account to calculate sensor nodes’ trust value, which is not enough for trust evaluation due to the widespread malicious attacks. In this paper, we propose an Efficient Distributed Trust Model (EDTM) for WSNs. First, according to the number of packets received by sensor nodes, direct trust and recommendation trust are selectively calculated. Then, communication trust, energy trust and data trust are considered during the calculation of direct trust. Furthermore, trust reliability and familiarity are defined to improve the accuracy of recommendation trust. The proposed EDTM can evaluate trustworthiness of sensor nodes more precisely and prevent the security breaches more effectively. Simulation results show that EDTM outperforms other similar models, e.g., NBBTE trust model. [ABSTRACT FROM AUTHOR]

Cooperative communication, which utilizes nearby terminals to relay the overhearing information to achieve the diversity gains, has a great potential to improve the transmitting efficiency in wireless networks. To deal with the complicated medium access interactions induced by relaying and leverage the benefits of such cooperation, an efficient Cooperative Medium Access Control (CMAC) protocol is needed. In this paper, we propose a novel cross-layer distributed energy-adaptive location-based CMAC protocol, namely DEL-CMAC, for Mobile Ad-hoc NETworks (MANETs). The design objective of DEL-CMAC is to improve the performance of the MANETs in terms of network lifetime and energy efficiency. A practical energy consumption model is utilized in this paper, which takes the energy consumption on both transceiver circuitry and transmit amplifier into account. A distributed utility-based best relay selection strategy is incorporated, which selects the best relay based on location information and residual energy. Furthermore, with the purpose of enhancing the spatial reuse, an innovative network allocation vector setting is provided to deal with the varying transmitting power of the source and relay terminals. We show that the proposed DEL-CMAC significantly prolongs the network lifetime under various circumstances even for high circuitry energy consumption cases by comprehensive simulation study. [ABSTRACT FROM AUTHOR]

Heterogeneous multiprocessors have been widely used in modern computational systems to increase the computing capability. As the performance increases, the energy consumption in these systems also increases significantly. Dynamic Voltage and Frequency Scaling (DVFS) is considered an efficient scheme to achieve the goal of saving energy, because it allows processors to dynamically adjust their supply voltages and/or execution frequencies to work on different power/energy levels. In this paper, we consider scheduling non-preemptive frame-based tasks on DVFS-enabled heterogeneous multiprocessor platforms with the goal of achieving minimal overall energy consumption. We consider three types of heterogeneous platforms, namely, dependent platforms without runtime adjusting, dependent platforms with runtime adjusting, and independent platforms. For these three platforms, we first formulate the problems as binary integer programming problems, and then, relax them as convex optimization problems, which can be solved by the well-known interior point method. We propose a Relaxation-based Iterative Rounding Algorithm (RIRA), which tries to achieve the task set partition, that is closest to the optimal solution of the relaxed problems, in every step of a task-to-processor assignment. Experiments and comparisons show that our RIRA produces a better performance than existing methods and a simple but naive method, and achieves near-optimal scheduling under most cases. We also provide comprehensive complexity, accuracy and scalability analysis for the RIRA approach by investigating the interior-point method and by running specially designed experiments. Experimental results also show that the proposed RIRA approach is an efficient and practically applicable scheme with reasonable complexity. [ABSTRACT FROM AUTHOR]

Time synchronization is one of the most fundamental services for wireless sensor networks. Prior studies have investigated the clock stability due to environmental dynamics. In this paper, we demonstrate by experiment that in spite of the surrounding environment, time synchronization is unavoidably impacted by in-network energy heterogeneity, which may incur up to 30-40 ppm clock uncertainty. We mathematically analyze the root cause of such clock uncertainty and propose a protocol called EATS. Sensor nodes with EATS can intelligently select the best synchronization parents that minimize the negative impact of the energy heterogeneity. The selection is robust to multiple impacting factors in the network and provides fine-grained synchronization accuracy. In addition, nodes can make use of local energy information and further calibrate the clocks. In light of this, the logic time maintained among different nodes is more consistent and the synchronization can be performed with a longer re-synchronization interval and less energy consumption. We implement EATS with TelosB motes and evaluate the effectiveness and efficiency of our design through extensive experiments and simulations. [ABSTRACT FROM PUBLISHER]