An Operational Semantics for Android Applications

This paper describes how virtual classes can be supported in a vir-tual machine. Main-stream virtual machines such as the Java Vir-tual Machine and the.NET platform dominate the world today, and many languages are being executed on these virtual machines even though their embodied design choices conflict with the design choices of the virtual machine. For instance, there is a non-trivial mismatch between the main-stream virtual machines mentioned above and dynamically typed languages. One language concept that creates an even greater mismatch is virtual classes, in particular be-cause fully general support for virtual classes requires generation of new classes at run-time by mixin composition. Languages like CaesarJ and Object Teams can express virtual classes restricted to the subset that does not require run-time generation of classes, be-cause of the restrictions imposed by the Java Virtual Machine. We have chosen to support virtual classes by implementing a special-ized virtual machine, and this paper describes how this virtual ma-chine supports virtual classes with full generality.

Instant messenger, often shortened to IM is one type of communication service that allows person to have a conversation (chat) privately with others via the internet. Within the calls & messaging on Android and iOS operating systems, they both have an equal value in the terms of innovation and performance. In this work, we focus on evaluate the performance of the IM application on Android and iOS operating systems used several criteria; delay, packet size, and throughput. We use two methods of data collection; primary and secondary data, and compare the IM application using simulation methods. Input parameters for this simulation is in the stanza form of a text message, and the output consists of delay, packet size, and throughput. The results of this work indicate that the IM on iOS operating system with criteria of delay, packet size and throughput can send and receive messages faster than IM on android operating system.

Wang et al. (Softw. Pract. Exper. 2007; 37(7):727–745) observed a phenomenon of performance inconsistency in the graphics of Java Abstract Window Toolkit (AWT)/Swing among different Java runtime environments (JREs) on Windows XP. This phenomenon makes it difficult to predict the performance of Java game applications. Therefore, they proposed a portable AWT/Swing architecture, called CYC Window Toolkit (CWT), to provide programmers with high and consistent rendering performance for Java game development among different JREs. They implemented a DirectX version to demonstrate the feasibility of the architecture. This paper extends the above research to other environments in two aspects. First, we evaluate the rendering performance of the original Java AWT with different combinations of JREs, image application programming interfaces, system properties and operating systems (OSs), including Windows XP, Windows Vista, Fedora and Mac OS X. The evaluation results indicate that the performance inconsistency of Java AWT also exists among the four OSs, even if the same hardware configuration is used. Second, we design an OpenGL version of CWT, named CWT‐GL, to take advantage of modern 3D graphics cards, and compare the rendering performance of CWT with Java AWT/Swing. The results show that CWT‐GL achieves more consistent and higher rendering performance in JREs 1.4 to 1.6 on the four OSs. The results also hint at two approaches: (a) decouple the rendering pipelines of Java AWT/Swing from the JREs for faster upgrading and supporting old JREs and (b) use other graphics libraries, such as CWT, instead of Java AWT/Swing to develop cross‐platform Java games with higher and more consistent rendering performance. Copyright © 2009 John Wiley & Sons, Ltd.

Hardware/software co-design and (re)configurable computing with field programmable gate arrays (FPGAs) are used to create a highly efficient implementation of the Java virtual machine (JVM). Guidelines are provided for applying a general hardware/software co-design process to virtual machines, as are algorithms for context switching between the hardware and software partitions. The advantages of using co-design as an implementation approach for virtual machines are assessed using several benchmarks applied to the implemented co-design of the JVM. It is shown that significant performance improvements are achievable with appropriate architectural and co-design choices. The co-designed JVM could be a cost-effective solution for use in situations where the usual methods of virtual machine acceleration are inappropriate.

Many widely used, latency sensitive, data-parallel distributed systems, such as HDFS, Hive, and Spark choose to use the Java Virtual Machine (JVM), despite debate on the overhead of doing so. This paper analyzes the extent and causes of the JVM performance overhead in the above mentioned systems. Surprisingly, we find that the warm-up overhead, i.e., class loading and interpretation of bytecode, is frequently the bottleneck. For example, even an I/O intensive, 1GB read on HDFS spends 33% of its execution time in JVM warm-up, and Spark queries spend an average of 21 seconds in warm-up.The findings on JVM warm-up overhead reveal a contradiction between the principle of parallelization, i.e., speeding up long running jobs by parallelizing them into short tasks, and amortizing JVM warm-up overhead through long tasks. We solve this problem by designing HotTub, a new JVM that amortizes the warm-up overhead over the lifetime of a cluster node instead of over a single job by reusing a pool of already warm JVMs across multiple applications. The speed-up is significant. For example, using HotTub results in up to 1.8X speedups for Spark queries, despite not adhering to the JVM specification in edge cases.

Various blocking operations, such as input/output (IO) operations, are an essential functionality of concurrent applications. However, these operations often cause efficiency-related challenges in multithreaded applications because of the single-thread access policy. IO operations' speed and efficiency heavily rely on operating system (OS) threads and scheduling processes, which is time consuming because of the insufficient distribution of OS resources. Because of their overgeneralization, required to support various usage scenarios, robust OS kernel threads are commonly heavyweight and oversized, created in a limited number, and heavily dependent on OS schedulers. Various asynchronous programming techniques tackled issues in implementing modern concurrent applications with blocking operations with the complete reconstruction of threads and their schedulers. Based on our previous preliminary research, we further explored a model of structured concurrency in Java Virtual Machine (JVM), through the updated implementation of virtual threads and accompanying schedulers, as a novel form of lightweight user-mode threads in the JVM, decoupled from OS threads and managed within the JVM. In this paper, we present our findings about the efficiency of those schedulers utilized for virtual threads on blocking operations, compared with the implementation of OS threads' schedulers, and review possibilities of reducing memory footprints and context switching costs.

While the Java Virtual Machine (JVM) plays a vital role in ensuring correct executions of Java applications, testing JVMs via generating and running class files on them can be rather challenging. The existing techniques, e.g., ClassFuzz and Classming, attempt to leverage the power of fuzzing and differential testing to cope with JVM intricacies by exposing discrepant execution results among different JVMs, i.e., inter-JVM discrepancies, for testing analytics. However, their adopted fuzzers are insufficiently guided since they include no well-designed seed and mutator scheduling mechanisms, leading to inefficient differential testing. To address such issues, in this paper, we propose SJFuzz, the first JVM fuzzing framework with seed and mutator scheduling mechanisms for automated JVM differential testing. Overall, SJFuzz aims to mutate class files via control flow mutators to facilitate the exposure of inter-JVM discrepancies. To this end, SJFuzz schedules seeds (class files) for mutations based on the discrepancy and diversity guidance. SJFuzz also schedules mutators for diversifying class file generation. To evaluate SJFuzz, we conduct an extensive study on multiple representative real-world JVMs, and the experimental results show that SJFuzz significantly outperforms the state-of-the-art mutation-based and generation-based JVM fuzzers in terms of the inter-JVM discrepancy exposure and the class file diversity. Moreover, SJFuzz successfully reported 46 potential JVM issues, and 20 of them have been confirmed as bugs and 16 have been fixed by the JVM developers.

We developed an architecture that automatically searches for and downloads Android applications from the Android Market. Furthermore, we created a detailed mapping of Android application programming interface (API) calls to the required permission(s), if any, for each call. We then performed an analysis of 141,372 Android applications to determine if they have the appropriate set of permissions based on the static analysis of the APK bytecode of each application. Our findings indicate that the majority of mobile software developers are notusing the correct permission set and that they either over-specify or under-specify their security requirements.

Java, as a safe and platform independent language, avoids access to low-level I/O devices or direct memory access. In standard Java, low-level I/O it not a concern; it is handled by the operating system. However, in the embedded domain resources are scarce and a Java virtual machine (JVM) without an underlying middleware is an attractive architecture. When running the JVM on bare metal, we need access to I/O devices from Java; therefore we investigate a safe and efficient mechanism to represent I/O devices as first class Java objects, where device registers are represented by object fields. Access to those registers is safe as Java's type system regulates it. The access is also fast as it is directly performed by the bytecodes getfield and putfield. Hardware objects thus provide an object-oriented abstraction of low-level hardware devices. As a proof of concept, we have implemented hardware objects in three quite different JVMs: in the Java processor JOP, the JIT compiler CACAO, and in the interpreting embedded JVM SimpleRTJ.

Scala is a new programming language developed at EPFL and incorporating the most important concepts of object-oriented and functional languages. It aims at integrating well with the Java and .NET platforms: their respective libraries are accessible without glue code, and the compiler can produce programs for both virtual machines. This thesis focuses on the compilation of two important concepts of Scala : mixin inheritance and run time types. The compilation techniques are presented in the context of the Java virtual machine, but could be adapted easily to other similar environments. Mixin inheritance is a relatively recent form of inheritance, offering new capabilities compared to single inheritance, without the complexity of multiple inheritance. We propose two implementation techniques for mixin inheritance: code copying and delegation. The implementation used in the Scala compiler is then presented and justified. Run time types make it possible for a program to examine the type of its values during execution. This possibility is interesting in itself, offering new capabilities to the programmer. Furthermore, run time types are also required to implement other high level concepts, like pattern matching, type-safe serialisation and reflection. We propose an implementation technique based on the representation of types as values, and show how to use the run time types of the underlying virtual machine to implement those of Scala. The techniques presented in this thesis have been implemented in our Scala compiler, scalac. This enabled us to evaluate these techniques, in particular their impact on the performances of programs. This evaluation was performed on several real, non-trivial programs.

Over the past few years, we can see the enormous increase of the use of smart phones that are based on android platform. Due to that reason, the mobile application development based on android has boosted the developers' interest. Having countless android application on the market is not an assurance of having users' satisfaction. Some of them do not reach users' expectations due to lack of research on dealing with android-based application requirements. With the fast growing of smart phones and their applications, the needs for better application to be produced are needed. Currently there is no specific research on analyzing the requirements for android applications. This paper proposes a new strategy that uses an activity theory to analyze the requirements of android application. It is then discusses a case study of a Muslim android application and presents the results of its requirements analysis using activity theory. The result of this study shows activity theory as an alternative requirement analysis approach to mobile application development that is based on android operating system.

Superblock compilation techniques such as control flow graph (CFG) or trace compilation have become a widely adopted approach to increase the performance of dynamically compiling virtual machines even further. While this was shown to be successful for many conventional virtual machines, it did not result in a higher performance for Java-based DBT machine emulators so far. These emulators dynamically translate application binaries of a target machine into Java bytecode, which is then eventually compiled into the native code of the emulating host by the Java Virtual Machine (JVM). Successful superblock compilation techniques for this class of emulators must consider the special requirements that result from the two-stage translation as well as the characteristics of the JVM, such as the inability of most Java JIT compilers to handle large bytecode methods efficiently. In this paper, we present a superblock compilation approach for a Java-based DBT machine emulator that generates a performance increase of up to 90 percent and of 32 percent on average. The key idea of our design is to provide a large scope over the control flow of target applications across basic block boundaries for the JVM, while still keeping small bytecode methods for the execution units. In addition, we also present two further optimizations -- interpreter context elimination and program counter elimination -- which increase the emulation performance by 16 percent again. In total, the optimization techniques discussed in this paper provide an average performance gain of 48 percent for the surveyed emulator.

Today’s complex applications must face the distribution of data and code among different network nodes. Computation in distributed contexts is demanding increasingly powerful languages and execution environments, able to provide programmers with appropriate abstractions and tools. Java is a wide-spread language that allows developers to build complex software, even distributed, but it cannot handle the migration of computations (i.e. threads), due to intrinsic limitations of many traditional JVMs. After analyzing the approaches in the literature, this paper presents our thread migration framework (called Mobile JikesRVM), implemented on top of the IBM Jikes Research Virtual Machine (RVM): exploiting some of the innovative techniques in the JikesRVM, we implemented an extension of its scheduler that allows applications to easily capture the state of a running thread and makes it possible to restore it elsewhere (i.e. on a different hardware architecture or operating system), but still with a version of the framework installed). Our thread serialization mechanism provides support for both proactive and reactive migration, available also for multi-threaded Java applications, and tools to deal with the problems of resource relocation management. With respect to previous approaches, we implemented Mobile JikesRVM without recompiling its JVM (Java Virtual Machine) source code, but simply extending JikesRVM functionalities with a full Java package to be imported when thread migration is needed.

In the Grid environment, user can manage and make use of web services, such as uploading or downloading web services. But when user wants to download one web services to run it in a local machine, one problem may occur: The web service can only be run on a special operating system, which is not the operating system that the user operates. To solve this problem, we need construct one middleware to emulate the running environment of the web service in the operating system that user operates. Middleware is the component created by the Operation System according to its metadata, and it is also the center from which the Internet technology extended. Component-based middleware has emerged as an important architectural component in modern distributed systems, such as XPCOM, UNO and the CORBA Component Model. Java Virtual Machine (JVM) is a middleware, aimed at making application cross platform to run. The goal of our research is to extend this work in order to exploit one component-based middleware platform that can make web services to run on different operating system platforms, such as Elastos, Windows and Linux operating system. In this paper, a new and efficient component model based on COM (ezCOM) is proposed. More specifically, this paper describes in detail how ezCOM can be used to construct a full component-based crossing Operating system middleware platform and also puts forward one new measure model to compare the performance of ezCOM, Wine-COM, XPCOM and UNO.

This paper describes how virtual classes can be supported in a virtual machine. Main-stream virtual machines such as the Java Virtual Machine and the .NET platform dominate the world today, and many languages are being executed on these virtual machines ...