Standard Java Virtual Machine Research Articles

JPR

Java PathFinder (JPF) is a backtrackable Java Virtual Machine (JVM), which is implemented in Java and runs on a standard JVM (e.g., Oracle HotSpot). Thus, a JPF developer can use off-the- shelf Java debuggers (e.g., jdb) when debugging code that makes up JPF. JPF explores all non-deterministic executions of a given target program and monitors for property violations. To facilitate debugging of the target program, JPF can capture and replay the execution trace that leads to a property violation. While the deterministic replay is invaluable, the replay with JPF does not allow the developer to attach an off-the-shelf Java debugger to the target program (e.g., step through the application code, set breakpoints, etc.). We present a technique, dubbed JPR, to improve the debugging experience of the JPF captured traces by migrating the JPF traces to a new format that can be executed using the standard JVM. JPR annotates each JPF trace, during the capture phase, with ex- tra data (e.g., instruction index, instruction count, etc.); the an- notated trace is then used to instrument Java bytecode to enforce the same execution trace on a standard JVM. JPR is compatible with various optimizations, e.g., state matching and partial-order reduction. We evaluated JPR on all multi-threaded Java pro- grams in the official JPF distribution. Our results show that JPR successfully replayed all JPF traces on the standard JVM with reasonable overhead during both recording and replaying.

JavAdaptor—Flexible runtime updates of Java applications

SUMMARYSoftware is changed frequently during its life cycle. New requirements come, and bugs must be fixed. To update an application, it usually must be stopped, patched, and restarted. This causes time periods of unavailability, which is always a problem for highly available applications. Even for the development of complex applications, restarts to test new program parts can be time consuming and annoying. Thus, we aim at dynamic software updates to update programs at runtime. There is a large body of research on dynamic software updates, but so far, existing approaches have shortcomings either in terms of flexibility or performance. In addition, some of them depend on specific runtime environments and dictate the program's architecture. We present JavAdaptor, the first runtime update approach based on Java that (a) offers flexible dynamic software updates, (b) is platform independent, (c) introduces only minimal performance overhead, and (d) does not dictate the program architecture. JavAdaptor combines schema changing class replacements by class renaming and caller updates with Java HotSwap using containers and proxies. It runs on top of all major standard Java virtual machines. We evaluate our approach's applicability and performance in non‐trivial case studies and compare it with existing dynamic software update approaches. Copyright © 2012 John Wiley & Sons, Ltd.

Complete and Platform-Independent Calling Context Profiling for the Java Virtual Machine

Calling context profiling collects statistics separately for each calling context. Complete calling context profiles that faithfully represent overall program execution are important for a sound analysis of program behavior, which in turn is important for program understanding, reverse engineering, and workload characterization. Many existing calling context profilers for Java rely on sampling or on incomplete instrumentation techniques, yielding incomplete profiles; others rely on Java Virtual Machine (JVM) modifications or work only with one specific JVM, thus compromising portability. In this paper we present a new calling context profiler for Java that reconciles completeness of the collected profiles and full compatibility with any standard JVM. In order to reduce measurement perturbation, our profiler collects platform-independent dynamic metrics, such as the number of method invocations and the number of executed bytecodes. In contrast to prevailing calling context profilers, our tool is able to distinguish between multiple call sites in a method and supports selective profiling of (the dynamic extent of) certain methods. We have evaluate the overhead introduced by our profiler with standard Java and Scala benchmarks on a range of different JVMs.

An application-level technique based on recursive hierarchical state machines for agent execution state capture

The capture of the execution state of agents in agent-based and multi-agent systems is a system feature needed to enable agent checkpointing, persistency and strong mobility that are basic mechanisms supporting more complex, distributed policies and algorithms for fault tolerance, load balancing, and transparent migration. Unfortunately, the majority of the currently available platforms for agents, particularly those based on the standard Java Virtual Machine, do not provide this important feature at the system-level. Several system-level and application-level approaches have been to date proposed for agent state execution capture. Although system-level approaches are effective, they modify the underlying virtual machine so endangering compatibility. Conversely, application-level approaches do not modify any system layer but they provide sophisticated agent programming models and/or agent converters that only allow a coarse-grain capture of agent state execution.In this paper, we propose an application-level technique that allows for a programmable-grain capture of the execution state of agents ranging from a per-instruction to a statement-driven state capture. The technique is based on the Distilled StateCharts Star (DSC*) formalism that offers an agent-oriented type of recursive hierarchical state machines. According to the proposed technique a single-threaded agent program can be translated into a DSC* machine, containing agent data, code and execution state, by preserving the original agent program semantics. The proposed technique can notably be applied to any agent program written through an imperative-style, procedural or object-oriented programming language. Currently, it is implemented in Java and fully integrated into the JADE framework, being JADE one of the most diffused agent platforms. In particular, agents, which are specified through a generic Java-like agent language, can be automatically translated into JADE agents according to the JADE DSCStarBehaviour framework by means of a translator tool. A simple yet effective running example is used to exemplify the proposed technique from modeling to implementation.

Class Transformations for Transparent Distribution of Java Applications.

The indirection of object accesses is a common theme for target domains as diverse as transparent distribution, persistence, and program instrumentation. Virtualizing accesses to fields and methods (by redirecting calls through accessor and indirection methods) allows interposition of arbitrary code, extending the functionality of an application beyond that intended by the original developer. We present class modifications performed by our RuggedJ transpar- ent distribution platform for standard Java virtual machines. RuggedJ abstracts over the location of objects by implementing a single object model for local and remote objects. However the implementation of this model is complicated by the presence of native and system code; classes loaded by Java's bootstrap class loader can be rewritten only in a limited manner, and so cannot be modified to conform to RuggedJ's complex object model. We observe that system code comprises the majority of a given Java application: an average of 78% in the applications we study. We consider the constraints imposed upon pervasive class transformation within Java, and present a framework for systematically rewriting arbitrary applications. Our system accommodates all system classes, allowing both user and system classes alike to be referenced using a single object model.

A family of real‐time Java benchmarks

AbstractJava is becoming a viable platform for real‐time computing. There are production and research real‐time Java VMs, as well as applications in both the military and civil sectors. Technological advances and increased adoption of real‐time Java contrast significantly with the lack of benchmarks. Existing benchmarks are either synthetic micro‐benchmarks, or proprietary, making it difficult to independently verify and repeat reported results. This paper presents the CDx benchmark, a family of open‐source implementations of the same application that target different real‐time virtual machines. CDx is, at its core, a real‐time benchmark with a single periodic task, which implements an idealized aircraft collision detection algorithm. The benchmark can be configured to use different sets of real‐time features and comes with a number of workloads. It can be run on standard Java virtual machines, on real‐time and Safety Critical Java virtual machine, and a C version is provided to compare with native performance. Copyright © 2010 John Wiley & Sons, Ltd.

Cross‐profiling for Java processors

AbstractPerformance evaluation of embedded software is essential in an early development phase so as to ensure that the software will run on the embedded device's limited computing resources. The prevailing approaches either require the deployment of the software on the embedded target, which can be tedious and may be impossible in an early development phase, or rely on simulation, which can be very slow. In this article, we introduce a customizable cross‐profiling framework for embedded Java processors, including processors featuring a method cache. The developer profiles the embedded software in the host environment, completely decoupled from the target system, on any standard Java virtual machine, but the generated profiles represent the execution time metric of the target system. Our cross‐profiling framework is based on bytecode instrumentation. We identify several pointcuts in the execution of bytecode that need to be instrumented in order to estimate the CPU cycle consumption on the target system. An evaluation using the JOP embedded Java processor as target confirms that our approach reconciles high profile accuracy with moderate overhead. Our cross‐profiling framework also enables the performance evaluation of new processor architectures before they are implemented. As a case study, we explore the performance impact of various processor design choices and optimizations, such as different cache sizes or pipeline organizations, and come up with an improved processor design that yields speedups of up to 40% on standard Java benchmarks. Copyright © 2009 John Wiley & Sons, Ltd.

Advanced runtime adaptation for Java

Dynamic aspect-oriented programming (AOP) enables runtime adaptation of aspects, which is important for building sophisticated, aspect-based software engineering tools, such as adaptive profilers or debuggers that dynamically modify instrumentation code in response to user interactions. Today, many AOP frameworks for Java, notably AspectJ, focus on aspect weaving at compile-time or at load-time, and offer only limited support for aspect adaptation and reweaving at runtime. In this paper, we introduce HotWave, an AOP framework based on AspectJ for standard Java Virtual Machines (JVMs). HotWave supports dynamic (re)weaving of previously loaded classes, and it ensures that all classes loaded in a JVM can be (re)woven, including the classes of the standard Java class library. HotWave features a novel mechanism for inter-advice communication, enabling efficient data passing between advices that are woven into the same method. We explain HotWave's programming model and discuss our implementation techniques. As case study, we present an adaptive, aspect-based profiler that leverages HotWave's distinguishing features.

Classifying Java class transformations for pervasive virtualized access

The indirection of object accesses is a common theme for target domains as diverse as transparent distribution, persistence, and program instrumentation. Virtualizing accesses to fields and methods (by redirecting calls through accessor and indirection methods) allows interposition of arbitrary code, extending the functionality of an application beyond that intended by the original developer. We present class modifications performed by our RuggedJ transparent distribution platform for standard Java virtual machines. RuggedJ abstracts over the location of objects by implementing a single object model for local and remote objects. However the implementation of this model is complicated by the presence of native and system code; classes loaded by Java's bootstrap class loader can be rewritten only in a limited manner, and so cannot be modified to conform to RuggedJ's complex object model. We observe that system code comprises the majority of a given Java application: an average of 76% in the applications we study. We consider the constraints imposed upon pervasive class transformation within Java, and present a framework for systematically rewriting arbitrary applications. Our system accommodates all system classes, allowing both user and system classes alike to be referenced using a single object model.

Java bytecode verification via static single assignment form

Java Virtual Machines (JVMs) traditionally perform bytecode verification by way of an iterative dataflow analysis. Bytecode verification is necessary to ensure type safety because temporary variables in the JVM are not statically typed. We present an alternative verification mechanism that transforms JVM bytecode into Static Single Assignment Form (SSA) and thereby propagates definitions directly to uses. Type checking at control flow merge points can then be performed in a single pass. Our prototype implementation of the new algorithm is faster than the standard JVM bytecode verifier. It has the additional benefit of generating SSA as a side effect, which may be immediately useful for a subsequent dynamic compilation stage.

Program transformations for light-weight CPU accounting and control in the Java virtual machine

This article constitutes a thorough presentation of an original scheme for portable CPU accounting and control in Java, which is based on program transformation techniques at the bytecode level and can be used with every standard Java Virtual Machine. In our approach applications, middleware, and even the standard Java runtime libraries (i.e., the Java Development Kit) are modified in a fully portable way, in order to expose details regarding the execution of threads. These transformations however incur a certain overhead at runtime. Further contributions of this article are the systematic review of the origin of such overheads and the description of a new static path prediction scheme targeted at reducing them.

Discretionary capability confinement

Motivated by the need of application-level access control in dynamically extensible systems, this work proposes a static annotation system for modeling capabilities in a Java-like programming language. Addressing a common critique of capability systems, the proposed annotation system can provably enforce capability confinement. This confinement guarantee is leveraged to model a strong form of separation of duty known as hereditary mutual suspicion. The annotation system has been fully implemented in a standard Java Virtual Machine.

A Platform-Independent Distributed Runtime for Standard Multithreaded Java

JavaSplit is a portable runtime environment for distributed execution of standard multithreaded Java programs. It gains augmented computational power and increased memory capacity by distributing the threads and objects of an application among the available machines. Unlike previous works, which either forfeit Java portability by using a nonstandard Java Virtual Machine (JVM) or compromise transparency by requiring user intervention in making the application suitable for distributed execution, JavaSplit automatically executes standard multithreaded Java on any heterogenous collection of Java-enabled machines. Each machine carries out its part of the computation using nothing but its local standard (unmodified) JVM. Neither the programmer nor the person submitting the program for execution needs to be aware of JavaSplit or its distributed nature. We evaluate the efficiency of JavaSplit on several combinations of operating systems, JVM implementations, and communication hardware.

A portable CPU-management framework for Java

The Java resource accounting framework, second edition (J-RAF2), is a portable CPU-management framework for Java environments. It is based on fully automated program-transformation techniques applied at the bytecode level and can be used with every standard Java virtual machine. J-RAF2 modifies applications, libraries, and the Java development kit itself to expose details regarding thread execution. This article focuses on the extensible runtime APIs, which are designed to let developers tailor management policies to their needs.

Mechanisms for secure modular programming in Java

AbstractWe present a new module system for Java that improves upon many of the deficiencies of the Java package system and gives the programmer more control over dynamic linking. Our module system provides explicit interfaces, multiple views of modules based on hierarchical nesting and more flexible name‐space management than the Java package system. Relationships between modules are explicitly specified in module description files. We provide more control over dynamic linking by allowing import statements in module description files to require that imported modules be annotated with certain properties, which we implement by digital signatures. Our module system is compatible enough with standard Java to be implemented as a source‐to‐source and bytecode‐to‐bytecode transformation wrapped around a standard Java compiler, using a standard Java virtual machine (JVM). Copyright © 2003 John Wiley & Sons, Ltd.

JRes

With the spread of the Internet the computing model on server systems is undergoing several important changes. Recent research ideas concerning dynamic operating system extensibility are finding their way into the commercial domain, resulting in designs of extensible databases and Web servers. In addition, both ordinary users and service providers must deal with untrusted downloadable executable code of unknown origin and intentions.Across the board, Java has emerged as the language of choice for Internet-oriented software. We argue that, in order to realize its full potential in applications dealing with untrusted code, Java needs a flexible resource accounting interface. The design and prototype implementation of such an interface --- JRes --- is presented in this paper. The interface allows to account for heap memory, CPU time, and network resources consumed by individual threads or groups of threads. JRes allows limits to be set on resources available to threads and it can invoke callbacks when these limits are exceeded. The JRes prototype described in this paper is implemented on top of standard Java virtual machines and requires only a small amount of native code.

Application of statistical analysis to determine the priority for improving LSI technology : Kazuyuki Saitoet al. IEEE Trans. Semicond. mfg5, 47 (1992)

The capture of the execution state of agents in agent-based and multi-agent systems is a system feature needed to enable agent checkpointing, persistency and strong mobility that are basic mechanisms supporting more complex, distributed policies and algorithms for fault tolerance, load balancing, and transparent migration. Unfortunately, the majority of the currently available platforms for agents, particularly those based on the standard Java Virtual Machine, do not provide this important feature at the system-level. Several system-level and application-level approaches have been to date proposed for agent state execution capture. Although system-level approaches are effective, they modify the underlying virtual machine so endangering compatibility. Conversely, application-level approaches do not modify any system layer but they provide sophisticated agent programming models and/or agent converters that only allow a coarse-grain capture of agent state execution.In this paper, we propose an application-level technique that allows for a programmable-grain capture of the execution state of agents ranging from a per-instruction to a statement-driven state capture. The technique is based on the Distilled StateCharts Star (DSC*) formalism that offers an agent-oriented type of recursive hierarchical state machines. According to the proposed technique a single-threaded agent program can be translated into a DSC* machine, containing agent data, code and execution state, by preserving the original agent program semantics. The proposed technique can notably be applied to any agent program written through an imperative-style, procedural or object-oriented programming language. Currently, it is implemented in Java and fully integrated into the JADE framework, being JADE one of the most diffused agent platforms. In particular, agents, which are specified through a generic Java-like agent language, can be automatically translated into JADE agents according to the JADE DSCStarBehaviour framework by means of a translator tool. A simple yet effective running example is used to exemplify the proposed technique from modeling to implementation.