Spark has garnered significant attention owing to its superior capability in processing vast amounts of data. Its executor-based model necessitates that sufficient resources are allocated to executors, thus facilitating the executions of diverse tasks. These tasks often exhibit different resource consumption patterns, resulting in time-varying resource consumption concerning CPU, network resources, etc. Consequently, this often leads to resource wastage. Some research endeavors have aimed to optimize the performance of Spark applications with time-varying CPU consumption. Their strategies primarily involve adjusting the number of executors dynamically. However, these efforts often overlook another crucial time-varying resource, namely, network bandwidth usage.To address this issue, this paper proposes a novel pre-transmission approach to optimize inter-stage communication in Spark. In essence, this approach leverages idle network bandwidth during the runtime of an upstream stage to initiate the transmission of outputs of its tasks in advance, which subsequently serve as the exactly input data of the tasks of corresponding downstream stages. Consequently, these tasks’ execution times are considerably reduced as most of their input data have already been in local nodes due to the pre-transmission approach. This leads to an overall enhancement in the performance of Spark applications. Our approach makes significant modifications to Spark’s internal working mechanism to achieve the pre-transmission, including extensions of the Spark Scheduler and Executor. Our experiments conducted utilizing the HiBench benchmark demonstrate that our approach can boost Spark applications’ performance by up to 31.3%, in comparison to the native Spark.

The Internet of medical things (IoMT) has become a promising paradigm, where the invaluable additional data can be collected by the ordinary medical devices when connecting to the Internet. The deep understanding of symptoms and trends can be provided to patients to manage their lives and treatments. However, due to the diversity of medical devices in IoMT, the codes of healthcare applications may be manipulated and tangled by malicious devices. In addition, the linguistic structures for layer activation in languages cause controls of layer activation to be part of program’s business logic, which hinders the dynamic replacement of layers. Therefore, to solve the above critical problems in IoMT, in this paper, a new approach is firstly proposed to support the dynamic replacement of layer in IoMT applications by incorporating object proxy into virtual machine (VM). Secondly, the heap and address are used to model the object and object evolution to guarantee the feasibility of the approach. After that, we analyze the influences of field access and method invocation and evaluate the risk and safety of the application when these constraints are satisfied. Finally, we conduct the evaluations by extending Java VM to validate the effectiveness of the proposal.

With the development of mobile devices, especially the emergence of smart phones, the mobile social networks (MSNs) have emerged to provide a variety of mechanisms for users to share their content. However, because the number of the mobile users still keeps growing rapidly, the MSNs become more complex than before and the features including evolution and topology need to be studied for communication system optimization. Therefore, in this paper, a great deal of data on social interactions among mobile users are collected to reveal the evolution and topological features of the MSNs. Firstly, the evolution feature of the MSN with the time is detailedly studied. Then, the statistical features of MSN including degree distribution, node distance, node closeness, and betweenness are analyzed. From the results of the analysis on the evolution features, we find that the MSN will become complex over time. In addition, the analysis of the topological properties shows that the MSN is a typical scale-free network and has strong small-world features.

This paper proposes a new speculative multithreading execution model which is suitable for object-oriented programs. Using this model, sequential object oriented programs are partitioned into multiple speculative object threads according to their structure and semantics by cooperated compiler and runtime system. Object threads as the basic units of parallel target code are mapped onto thread units of target machine dynamically. However, synchronous message passing between objects in source program prevents object threads in target code from execution in parallel at its synchronous points. By speculating the execution of message passing in object-oriented programs, we can convert synchronous message passing into speculative asynchronous message passing, then we can not only decrease the synchronization overhead in runtime but also exploit more parallelism for such programs. The runtime system verifies speculative asynchronous message passing by comparing it with non-speculative synchronous message passing in order to keep the parallel execution predicable and deterministic. This model is implemented as a prototype system Rope for evaluation. Experiments with Java version of Olden benchmark suite show that this model takes a good accelerating effect for object-oriented programs.

In Speculative Multithreading, data dependence that limits the speedup of speculative parallelization needs to be resolved to achieve a high performance. This paper designs a synchronization execution model, with the support of compiler, to synchronize store and load instructions that frequently have data dependence on each other. We use hardware profiler to gather dependence violation information of memory data, and the profiler information is fed back to the compiler. The compiler analyzes the synchronization efficiency, select store/load pairs of great synchronization potential, and inserts synchronization instructions using insertion algorithm. Loop threads and non-loop threads can both be synchronized. The hardware support is also given in the paper. The experimental results show that the synchronization under the compiler support can effectively resolve some memory data dependence and improve the performance of the speculative execution.