JBInsTrace: A tracer of Java and JRE classes at basic-block granularity by dynamically instrumenting bytecode

Understanding what happens during the runtime of a Java program is difficult. Tracking runtime flow can bring valuable information for program understanding and behavior analysis. Polymorphism, thread concurrency or even simple facts like the number of method invocations and the number of executed bytecodes are valuable information to track, but are difficult to compute outside the Java Virtual Machine (JVM) on running programs. In this paper, we present JBInsTrace, a new tool that instruments and traces Java bytecode. It produces static information about source code and a very fine grained trace of Java software execution, combining them to allow detailed analysis of the runtime. Our tool differs from others because it does not only trace program classes but also JRE classes, and does so at basic block level, without altering the JVM and without statically modifying class files. We explain JBInsTrace design, focused towards efficiency, which results in reasonable performance penalty.     

Model variables: cleanly supporting abstraction in design by contract

In design by contract (DBC), assertions are typically written using program variables and query methods. The lack of separation between program code and assertions is confusing, because readers do not know what code is intended for use in the program and what code is only intended for specification purposes. This lack of separation also creates a potential runtime performance penalty, even when runtime assertion checks are disabled, due to both the increased memory footprint of the program and the execution of code maintaining that part of the program's state intended for use in specifications. To solve these problems, we present a new way of writing and checking DBC assertions without directly referring to concrete program states, using ‘model’, i.e. specification‐only, variables and methods. The use of model variables and methods does not incur the problems mentioned above, but it also allow one to write more easily assertions that are abstract, concise, and independent of representation details, and hence more readable and maintainable. We implemented these features in the runtime assertion checker for the Java Modeling Language (JML), but the approach could also be implemented in other DBC tools. Copyright © 2005 John Wiley & Sons, Ltd.     

JavAdaptor—Flexible runtime updates of Java applications

Software 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.     

Systematic literature review of the objectives,techniques, kinds,and architectures of models at runtime

In the context of software development, models provide an abstract representation of a software system or a part of it. In the software development process, they are primarily used for documentation and communication purposes in analysis, design, and implementation activities. Model-Driven Engineering (MDE) further increases the importance of models, as in MDE models are not only used for documentation and communication, but as central artefacts of the software development process. Various recent research approaches take the idea of using models as central artefacts one step further by using models at runtime to cope with dynamic aspects of ever-changing software and its environment. In this article, we analyze the usage of models at runtime in the existing research literature using the Systematic Literature Review (SLR) research method. The main goals of our SLR are building a common classification and surveying the existing approaches in terms of objectives, techniques, architectures, and kinds of models used in these approaches. The contribution of this article is to provide an overview and classification of current research approaches using models at runtime and to identify research areas not covered by models at runtime so far.     

Dynamic Event Generation for Runtime Checking using the JDI

Approaches to runtime checking have to track the execution of a software system and therefore have to deal with generating and processing execution events. Often these techniques are applied at the code level – either by inserting new source code prior to the compilation or by modifying the target code, e.g. Java byte code, before running the program.The jassda [4,3] framework and tool enable runtime checking of Java programs against a CSP-like specification. For generating events it uses the Java Debug Interface (JDI) and thus no modifications to the code are necessary. Another advantage is that events are generated on demand, i.e. dynamically at runtime it is determined which events to generate for the current debug run without modifying the program itself. This paper shows how this event generation is done by the jassda framework.     

Experiences building a communication‐oriented JavaOS

Mobile code makes it easier to maintain, debug, update, and customize a system. Active networks are one of the more interesting applications of mobile code: code is injected into the nodes of a network to customize the network's functionality, such as routing, and to add new features, such as special‐purpose congestion control and filtering algorithms. The challenge is to develop a communication‐oriented platform for such systems. We refer to mobile code targeted at low‐level, communication‐oriented systems like active networks as liquid software, the key distinction being that liquid software is focused on the efficient transfer of data, not high‐performance computation. To this end, we have designed and implemented Joust, which consists of a complete re‐implementation of the Java virtual machine (including both the runtime system and a just‐in‐time compiler), running on the Scout operating system (a configurable, communication‐oriented OS). The result is a configurable, high‐performance platform for running liquid software. We present the results of implementing two different applications of liquid software on Joust, including a prototype architecture for active networks. Copyright © 2000 John Wiley & Sons, Ltd.     

The Hydra Parallel Programming System

The Hydra Parallel Programming System, a new parallel language extension to Java, and its supporting software are described. It is a fairly simple yet powerful language designed to address a number of areas that have not received much attention. One of these areas is the recompilation of parallel programs at runtime to allow a parallel program to adapt to the architecture it is executing on. The first version of this software system focuses on smaller Symmetric Multiprocessing and compatible architectures which are becoming more common. This particular class of machines has a great need for more options in the area of parallel programming among the vastly popular Java language programmers. Hydra programs will run as sequential Java on machines that do not have the parallel support or do not have an implemented Hydra runtime system without requirement of any modifications to the program. This paper describes the language, compares it with other languages (specifically with JOMP, an OpenMP implementation for Java), presents a brief discussion on compiling and executing Hydra programs, presents some sample benchmarks and their performance on three platforms, and concludes with a discussion of issues and future directions for Hydra. Copyright © 2007 John Wiley & Sons, Ltd.     

Design and implementation of Java just-in-time compiler

Early Java implementations relied on interpretation,leading to poor performance compared to compiled programs,Java just-in-time(JIT) compiler can compile Java programs at runtime,so it not only improves Java‘s performance prominently,but also preserves Java‘s portability.In this paper the design and implementing techniques of Java JIT complier based on Chinese open system are discussed in detail.To enhance the portability,a translating method which combines the static simulating method and macro expansion method is adopted.The optimization technique for JIT compiler is also discussed and a way to evaluate the hotspots in Java programs is presented.Experiments have been conducted to verify JIT compilation technique as an efficient way to accelerate Java.     

Runtime Engine for Dynamic Profile Guided Stride Prefetching

Stride prefetching is recognized as an important technique to improve memory access performance. The prior work usually profiles and/or analyzes the program behavior offline, and uses the identified stride patterns to guide the compilation process by injecting the prefetch instructions at appropriate places. There are some researches trying to enable stride prefetching in runtime systems with online profiling, but they either cannot discover cross-procedural prefetch opportunity, or require special supports in hardware or garbage collection. In this paper, we present a prefetch engine for JVM （Java Virtual Machine）. It firstly identifies the candidate load operations during just-in-time （JIT） compilation, and then instruments the compiled code to profile the addresses of those loads. The runtime profile is collected in a trace buffer, which triggers a prefetch controller upon a protection fault. The prefetch controller analyzes the trace to discover any stride patterns, then modifies the compiled code to inject the prefetch instructions in place of the instrumentations. One of the major advantages of this engine is that, it can detect striding loads in any virtual code places for both regular and irregular code, not being limited with plain loop or procedure scopes. Actually we found the cross-procedural patterns take about 30% of all the prefetchings in the representative Java benchmarks. Another major advantage of the engine is that it has runtime overhead much smaller （the maximal is less than 4.0%） than the benefits it brings. Our evaluation with Apache Harmony JVM shows that the engine can achieve an average 6.2% speed-up with SPECJVM98 and DaCapo on Intel Pentium 4 platform, in spite of the runtime overhead.     

基于移动Agent的无线应用软件测试系统

介绍了基于移动Agent技术实现的用于测试与网络相关的无线应用软件的测试系统,并提出了将系统的弱移动机制改造成为强移动的新思路用以提高测试环境的真实性。利用了对源程序插入代码来捕捉和恢复程序状态的方法,加入的代码在程序需要捕捉状态时捕捉到程序状态信息并在重新运行时恢复状态。实现了在不修改Java虚拟机的情况下基于Java的移动Agent强迁移。     

Java动态类加载机制及其应用

Java动态类加载机制是Java虚拟机(JVM)的一个重要特征。它实现了在程序执行的过程中动态地加载所需要的类文件，并且这种动态行为是可以人为控制的。这使得Java语言平台具有在运行期间安装软件组件的能力。通过对Java类加载器的原码进行分析，阐述了Java动态类加载机制的原理和过程，并通过一个客户端服务器(C／S)模式下动态地更新客户端软件功能的例子，说明了Java动态类加载机制的实际应用。     

Enhancing Java server availability with JAS

The Java programming language is increasingly used in the implementation of servers with stringent availability, reliability, and performance requirements. Our Java Application Supervisor (JAS) software system is an attachment to a Java runtime environment that enhances the availability of a target Java program. To this end, JAS automatically detects and resolves certain reliability and performance problems during the execution of the target program. JAS does not require any source or byte code modifications in the target program. Instead, JAS is configured for a target program by supplying simple policies that determine how JAS reacts to problems during the target program execution. JAS typically imposes little execution time and memory overhead on the target program. We describe an experiment with a Web proxy that exhibits reliability and performance problems under heavy load. In this experiment, running the proxy in conjunction with JAS increased the rate of successful requests to the proxy by 33% and decreased the averagerequest processing time by 22%. JAS was also used successfully in two Java servers at Bell Labs to monitor server reliability and performance and ensure long‐term availability. Copyright © 2001 John Wiley & Sons, Ltd.     

A type system for static and dynamic checking of C++ pointers

Object-oriented programming is the most used programming paradigm when dealing with large-scale, modular software. In this field, the two leading languages are Java and C++. The former has superior qualities in terms of safety and ease of programming, whereas the latter is often considered an “old” language, too complex and potentially unsafe.In this paper, we describe a new type system designed to analyze the security problems derived from pointer manipulation in C++. This type system tries to trap the most common errors through static analysis, i.e., at compile-time, and only when static analysis fails it generates and embeds code fragments that apply runtime checks on specific instructions. The aim of this new type system is to give C++ the same safety of Java in the most important memory-related operations, without adding much runtime overhead. An experimental implementation of the type system is also presented, embedded in a C++ analysis tool called GPCC.     

一种中间件服务容错配置管理方法

提出一种基于运行时刻软件体系结构的容错管理方法,支持开发者和管理员针对不同中间件服务失效定制合适的故障检测和修复机制.首先,运行时刻软件体系结构自动构造构件依赖视图和错误传播①视图,为理解和分析整个系统的可靠性提供全局视图;然后,操作运行时刻软件体系结构配置容错机制;最后利用AOP技术将容错机制插装到中间件中,使其具备指定的容错能力.上述过程在一个可视化工具的辅助下半自动实施,并在J2EE中间件上得到验证.     

Quantifying the Benefits of SSA-Based Mobile Code

High-performance just-in-time compilers for Java need to invest considerable effort before actual code generation can commence. This is in part due to the very nature of the Java Virtual Machine, which is not well matched to the requirements of optimizing code generators. Alternative transportation formats based on Static Single Assignment form should theoretically be superior to virtual machines, but this claim has not previously been validated in practice. This paper revisits the topic and attempts to quantify the effect of using an SSA-based mobile code representation (IR) instead of a virtual-machine based one.To this end, we have integrated full support for a verifiable SSA-based IR into Jikes RVM, an existing Java execution environment. The resulting system is capable of loading and executing Java programs represented in either format, traditional JVM bytecode as well as the SSA-based representation, and it can even execute programs made up of a mixture of the two formats. In our implementation, the two alternative just-in-time compilation pipelines share a common low-level code generator.Performance results are encouraging and show simultaneous improvements in both compilation time and code quality relative to Jikes RVM's standard optimizing compiler for JVM class files. They support the hypothesis that SSA-based intermediate representations offer advantages in the context of just-in-time compilation.     

Towards Language-Agnostic Mobile Code

The Java Virtual Machine is primarily designed for transporting Java programs. As a consequence, when JVM bytecodes are used to transport programs in other languages, the result becomes less acceptable the more the source language diverges from Java. Microsoft's .NET transport format fares better in this respect because it has a more flexible type system and instruction set, but it is not extensible, and (for example) has no provision for supporting explicit programmer-specified parallelism. Both platforms have difficulty making transported programs run efficiently.This paper discusses first steps towards mobile code representations that are independent (in the sense that the representation can be appropriately parameterized) of the source language (e.g., Java), intermediate representation (e.g., bytecode), and target architecture (e.g., x86). We call this kind of parameterizable framework language-agnostic.We present two techniques which provide parts of the envisioned language-agnostic functionality. Compressed abstract syntax trees as a wire format provide for a very dense encoding of programs at a high level of abstraction. We show how to parameterize the compression algorithm in a modular fashion with knowledge beyond the purely syntactical level. This leads to the notion of well-formedness by construction. The second technique defines the semantics of programs by mapping from abstract syntax trees to a typed core calculus representation. Based on this representation it becomes possible to use portable definitions of security policies and to execute programs written in different source languages, even if a more efficient trusted native compiler is not available on the target platform.     

Four Trends Leading to Java Runtime Bloat

The drive to rapidly develop layered, interconnected, and flexible systems has eclipsed consideration of resource costs. Consequently, large Java applications suffer from runtime bloat: a large and pervasive infrastructure tax, where simple transactions require a few hundred thousand method calls, and a server with 1 Gbyte of memory sometimes can only support a few hundred users. Current Java optimizers and garbage collectors are of little help for these systemic problems. Enterprises face greatly reduced scalability, increased power consumption, and missed deliveries. In this article, the authors detail four global software development trends, along with some widely held myths, that lead to bloat in Java applications. They illustrate their consequences with anecdotes drawn from real applications suffering severe performance and memory issues. While these trends are inevitable, runtime bloat is not. Understanding the sources of bloat can help programmers craft appropriate solutions for the future.