Sharing of Cluster Resources among Multiple Workflow Applications

We study the problem of scheduling periodic-time-critical tasks on a multiprocessor system. A periodic-time-critical task consists of a certain number of computations, each arising at a fixed interval of time, called the period of the task. The ratio of the computation time to the period is called the utilization factor of the task. Each computation has a prescribed deadline which must be guaranteed to be met, failing which there is likely to result an irrepairable loss. The scheduling problem is to specify the processor on which a computation is to be made and the order in which such computations will be made, such that every computation meets its deadline. The goal is to minimize the number of processors needed. The problem is NP-complete. As such, we devise a heuristic algorithm and analyze its performance. The algorithm assigns tasks based on the utilization factors of the tasks. We analyze the worst case performance of the algorithm by obtaining bounds on the ratio of the maximum number of processors needed by the algorithm to the minimum number of processors required. It is shown that this ratio is 2.

The scheduling of tasks with deadlines on clusters is a key issue for offering quality-of-service (QoS) assurance. A critical challenge in real-time task scheduling is to handle various types of applications. This paper investigates the scheduling problem for processing a set of tasks comprising both divisible and indivisible real-time tasks on cluster systems. Indivisible tasks are characterized by the property that they need to be processed on their entirety on a single processor while divisible tasks can be distributed across several processing nodes by exploiting the underlying data parallelism. We propose a dynamic (on-line) real-time scheduling algorithm referred to as Hybrid Loads Push-Pull Scheduling (HLPPS) algorithm for handling a set of tasks comprising both divisible and indivisible real-time tasks on cluster systems. HLPPS is shown to efficiently exploit the parallelism in divisible tasks without undermining the schedulability of indivisible tasks and thereby optimize the overall performance. We consider two distinct network platforms - tightly coupled and loosely coupled clusters in designing the strategy. We conduct extensive performance evaluation studies to quantify the performance of the proposed algorithm under a variety of scenarios.

Nowadays, Graphics Processing Units (GPUs) dominate in a wide spectrum of computing realms with massive parallel processing capabilities. However, as resources are continuously integrated into GPUs, traditional serial execution often leads to underutilization. Prior studies have shown that allowing multiple kernels to run concurrently and share GPU resources can effectively improve both resource utilization and system throughput. Nonetheless, existing methods for solely automating concurrent kernel execution either schedule kernels within individual applications (i.e., kernel-level) or enable task concurrency across multiple applications (i.e., task-level), thus leaving substantial GPU capacity underexploited. Moreover, they inevitably introduce new programming frameworks, which incur cumbersome manual efforts and further impose substantial programming burdens on developers. To address these limitations, we propose HuntKTm , a hybrid scheduling and automatic management method that cooperates kernel-level and task-level concurrency to enhance system throughput with minimal code modification. Specifically, HuntKTm comprises a stream scheduler to assign kernels, a task scheduler to dispatch tasks onto GPUs, and a memory manager to reduce memory footprint. The stream scheduler applies a strategy to dispatch kernels to hardware queues and adopts a novel algorithm to remove redundant synchronizations in computational flow. Then, the task scheduler automatically issues tasks based on resource requirements and availability to support GPU sharing among uncooperative applications. Finally, the memory manager reduces memory footprint for tasks by limiting the lifetimes of memory objects, which thereby enables more tasks to execute simultaneously. Experimental results demonstrate that HuntKTm improves system throughput by 33.2% over the existing state-of-the-art CASE framework on a single machine equipped with four NVIDIA A100 GPUs and reaches 13.8% higher application-level performance over Taskflow, even with lessened programming efforts.

Resource provisioning and scheduling are essential challenges in handling multiple workflow requests within cloud environments, particularly given the constraints imposed by limited resource availability. Although workflow scheduling has been extensively studied, few methods effectively integrate resource provisioning with scheduling, especially under cloud resource limitations and the complexities of multiple workflows. To address this challenge, we propose an innovative two-stage genetic-based optimization approach. In the first stage, candidate cloud resources are selected for the resource pool under the given resource constraints. In the second stage, these resources are provisioned and task scheduling is optimized on the selected resources. A key advantage of our approach is that it reduces the search space in the first stage through a novel encoding scheme that enables a caching strategy, in which intermediate results are stored and reused to enhance optimization efficiency in the second stage. The proposed solution is evaluated through extensive simulation experiments, assessing both resource selection and task scheduling across a diverse range of workflows. The results demonstrate that the proposed approach outperforms existing algorithms, particularly for highly parallel workflows, highlighting its effectiveness in managing complex workflow scheduling under resource-constrained cloud environments.

This paper analyzes the impact of dynamic task scheduling, processing element allocation and data transfer management on system performance of heterogeneous MPSoCs. Therefore, all parts of a runtime scheduling unit are analyzed. Bottlenecks are identified and their complexity evaluated. Furthermore, traced information is processed with two newly introduced tools. The first one generates an annotated SDF3 file. The second one creates a static schedule which applies the same scheduling and allocation decision as the dynamic scheduler. The execution of the static schedule reduces the burden of task management to a minimum. The resulting static execution is compared with the execution of the dynamic schedule. Hence, runtime overhead of dynamic scheduling is unveiled.

In this article, we study the dynamic scheduling problem of maintenance tasks in a distributed environment. This environment is presented as a center of competence related to several sites. The human resources have not the same qualification, and then, the assignment decision has to take care of several parameters principally with particular competences. Our contribution concerns the optimal insertion of a new task in an existing scheduling. The proposed method is based on a combination of a local decent algorithm and the Kangaroo methodology. The objective function is to minimize the following criteria: the total weighted tardiness, the standard deviation between resources and the number of task which could have a new assignment (assigned to a new resource). The main of the algorithm is to disturb as less as possible the existing scheduling. The obtained results are validated and compared to the results obtained by static scheduling.

The massive growth of cloud computing leads to huge amounts of energy consumption and release of carbon footprints as data centers are housed by a large number of servers. Consequently, the cloud service providers are looking for eco-friendly solutions to reduce energy consumption and carbon emissions. As a result, task scheduling has drawn attention, in which efficient resource utilization and minimum energy consumption take into great consideration. This is an exigent issue, especially for the heterogeneous environment. In this work, we put forward an energy-efficient task scheduling algorithm (ETSA) to address the demerits associated with task consolidation and scheduling. The proposed algorithm ETSA takes into account the completion time and total utilization of a task on the resources, and follows a normalization procedure to make a scheduling decision. We evaluate the proposed algorithm ETSA to measure energy efficiency and makespan in the heterogeneous environment. The experimental results are compared with recent algorithms, namely random, round robin, dynamic cloud list scheduling, energy-aware task consolidation, energy-conscious task consolidation and MaxUtil. The proposed algorithm ETSA provides an elegant trade-off between energy efficiency and makespan than the existing algorithms.

<span>The distributed fog node network and variable workloads make task distribution difficult in fog computing. Optimizing computing resources for dynamic workloads with heuristic and metaheuristic algorithms has shown potential. To address changing workloads, these algorithms enable real-time decision-making. This systematic review examines heuristic, meta-heuristic, and real-time dynamic job scheduling strategies in fog computing. Static methods like heuristic and meta-heuristic algorithms can help modify dynamic task scheduling in fog computing situations. This paper covers a current study area that stresses real-time approaches, meta-heuristics, and fog computing environments' dynamic nature. It also helps build reliable and scalable fog computing systems by spotting dynamic task scheduling trends, patterns, and issues. This study summarizes and analyzes the latest fog computing research on task-scheduling algorithms and their pros and cons to adequately address their issues. Fog computing task scheduling strategies are detailed and classified using a technical taxonomy. This work promises to improve system performance, resource utilization, and fog computing settings. The work also identifies fog computing job scheduling innovations and improvements. It reveals the strengths and weaknesses of present techniques, paving the way for fog computing research to address unresolved difficulties and anticipate future challenges.</span>

Energy minimization in dynamic train scheduling and control for metro rail operations

Reconfigurable devices (RDs) are extremely advantageous when employed in real-time embedded systems. Nonetheless, they are susceptible to soft errors. In a broad sense, the present research addresses the challenge of improving the reliability of independent periodic real-time hardware tasks in RDs by utilizing hybrid fault-tolerant scheduling. The current paper combines static and dynamic real-time scheduling techniques to improve the reliability of the system. First, the proposed algorithm statically schedules primary tasks and preserves area and time for possible backup tasks on the RD. The overlapping of passive backup tasks is possible. Next, at the run time, event-triggered dispatcher dynamically determines which candidate backup copy should be selected for configuration on the overloaded preserved areas. Reliability, task deadline, and RD area limitations are the determining factors of backup overloading in the static phase. On the other hand, in the dynamic phase, the execution result of the primary tasks—in this case, success or failure—is the deciding factor based on which the dispatcher configures the true backup task on the preserved area. Experimental results show that the hybrid scheduling technique enhances the mean-time-to-failure of the system by an average factor of 1.22 in comparison with a similar state-of-the-art study.

Clustering and scheduling of tasks for parallel implementation is a well researched problem. Several techniques have been presented in the literature to improve performance and reduce problem execution times. In this paper we present a novel approach where clustering and scheduling of tasks can be tuned to achieve maximal speedup or efficiency. The proposed scheme is based on the relation between the costs of computation and communication of task clusters. In this paper we show how clustering can be adapted to suit different architectures and number of available processors. The proposed efficient clustering and scheduling algorithm is flexible: the clustering and scheduling can be tuned to suit bounded or unbounded number of processors and/or parallel computing environment. Comparative studies indicate superior efficiency compared to most other schemes proposed in recent years.

Enhanced wireless communication improves the connectivity of vehicular networks in which vehicles are utilized as infrastructures for communication and computation. Thus, a new concept “Vehicular Edge Computing (VEC)” is formed. As VEC utilizes a collaborative multitude of near-user edge resources (i.e. vehicles) in the Internet of Vehicles, the capability of these joint resources becomes heterogeneous especially in their movements. Therefore, one critical problem is how to efficiently schedule each task under such mobile environments. For the reason, we propose a hybrid dynamic scheduling scheme (HDSS) that has the ability to optimize the task scheduling dynamically based on the changeable system environments. HDSS provides a decision function (DF) to select a better-performed scheduling algorithm from two provided candidates: the queue-based dynamic scheduling (QDS) algorithm and the time-based dynamic scheduling (TDS). QDS coincides with the Join-the-Shortest Queue scheme, which decides the scheduling by sorting out a server with the shortest queue-length; nevertheless, TDS is novel scheme that is designed to implement task allocation by estimating the waiting time of each server in order to select a server with the fastest response. Finally, this research generates formal models of each scheduling algorithm and the hybrid scheduling scheme to conduct performance evaluation with a fluid flow approximation technique. The analysis results in a superior performance of HDSS in the unstable VEC environments.

Coarse-grained reconfigurable architectures (CGRAs) are increasingly employed as domain-specific accelerators due to their efficiency and flexibility. A CGRA typically relies on compilers to perform task scheduling. The longstanding problem of static scheduling is that it suffers from insufficient parallelism in handling irregularities due to over-serialization and workload imbalance, which leads to severe resource underutilization and performance loss. To counteract the limitations of static scheduling in CGRAs, it is essential to exploit dynamic parallelism automatically and manage hardware resources adaptively. However, existing dynamic scheduling mechanisms, e.g., work stealing, often reschedule aggressively for instant performance but sacrifice efficiency, which is unfavorable to CGRAs that emphasize efficiency and fewer reconfigurations. This article proposes an elastic task scheduling scheme that enables lightweight dynamic scheduling in CGRAs. Tasks are rescheduled at runtime according to the classic tagged-token dataflow paradigm to enable dynamic task-level parallelism. Meanwhile, tasks are dynamically resized according to run-time throughputs via duplication, combination, and substitution operators for balanced multitask execution. We implement the elastic task scheduling scheme on a well-known reconfigurable architecture - triggered instruction architecture (TIA). Evaluation on the MachSuite benchmarks shows that the proposed scheme is effective in improving performance and energy efficiency. The average speedup is 2× over the baseline. Also, our design attains a 57 percent improvement in the area-normalized performance and a 49 percent better energy efficiency. Compared with a state-of-the-art dynamic scheduling method, our scheme achieves 1.6× speedup and 1.6× energy efficiency than work-stealing mechanism on the same substrate.

Static task scheduling in distributed computing systems is a very complex problem and known to be NP-hard. This problem is even harder when the module execution times become probabilistic. In this paper we study the effect of probabilistic module execution times on the performance of task-scheduling algorithms. We show that in static task scheduling, for probabilistic module execution times, and in the existence of some factors there is no need to use an expensive task-scheduling algorithm. Given any two static task-scheduling algorithms that use deterministic module execution times in assigning task modules to the distributed system, the performance of these two algorithms will not remain the same when these module execution times become probabilistic rather than deterministic. We also study the effects of some factors an our results.

A parallel circuit simulator, iPRIDE, which uses a direct solution method and runs on a shared-memory multiprocessor is described. The simulator is based on a multilevel node tearing approach which produces a nested bordered-block-diagonal (BBD) form of the circuit equation matrix. The parallel solution of the nested BBD matrix is described. Its efficiency is shown to depend on how the circuit is partitioned as well as the sequence in which the concurrent tasks (scheduling) are solved. A partitioning heuristic is proposed, assuming that an arbitrary number of processors is available. Scheduling methods are studied when the number of processors is fixed. A method for determining the optimal level of partitioning, which depends on the number of processors as well as the scheduling methods, is described. The program is implemented on an ALLIANT FX/8 multiprocessor with shared memory. The performance of the program is reported. >