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International Conference on Embedded Systems and Applications (ESA 05)

作者： Desai, A Cain, G Singh, J Veljanovski, R Victoria Univ Technol Ctr Telecommun & Microelect Melbourne Vic Australia

ISBN: (纸本)193241553X

In spite of the popularly of java, its slow performance and unpredictable execution characteristics are still some of the most challenging issues faced by designers for real-time applications. In the past, numerous architectural enhancements have been investigated to enhance performance and increase predictability. In this paper, dedicated hardware based enhancements that can complement existing design solutions are presented. To achieve high-performance while maintaining simplicity of design, a nested state controller is used for modelling java instructions. This approach enables ahead of synthesis resource sharing and simplified reuse of functional elements. A hardware based automatic memory management sub-system is also presented that provides virtual pointer based memory access for memory allocations. Along with fixed cycle allocation and fast automatic resizing of memory, the memory controller provides predictable management functions. The paper describes a simple system targeted to the Virtex II Pro FPGA.

关键词： java virtual machine real-time java memory management nested state machines

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On the design of the local variable cache in a hardware translation-based java virtual machine 05

On the design of the local variable cache in a hardware tran...

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Conference on Languages, Compilers and Tools for Embedded Systems

作者： Oi, H Univ Aizu Dept Comp Sci Aizu Wakamatsu Japan

ISBN: (纸本)9781595930187

Hardware bytecode translation is a technique to improve the performance of the java virtual machine (JVM), especially on the portable devices for which dynamic compilation is infeasible. However, since the translation is done on a single bytecode basis, it is likely to generate frequent memory accesses for local variables which can be a performance bottleneck. In this paper, we propose to add a small register file to the datapath of the hardware-translation based JVM and use it as a local variable cache. We evaluate the effectiveness of the local variable cache against the size of the local variable cache which determines the chip area overhead and the operating speed. We also discuss the mechanisms for the efficient parameter passing and the on-the-fly profiling. With two types of exceptions, a 16-entry local variable cache achieved hit ratios of 60 to 98 %. The first type of exceptions is represented by the FFT, which accesses more than 16 local variables. In this case, on-the-fly profiling was effective. The hit ratio of 16-entry cache for the FFT was increased from 44 to 83 %. The second type of exception is represented by the SAXON XSLT processor for which cold misses were significant. The proposed parameter passing mechanism turned 6.4 to 13.3 % of total accesses from miss to hit to the local variable cache.

关键词： java virtual machine hardware-translation memory hierarchy

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Exploiting Multi-Core Processors to Improve Time Predictability for Real-time java Computing

Exploiting Multi-Core Processors to Improve Time Predictabil...

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IEEE International Conference on Embedded and Real-Time Computing Systems and Applications

作者： Yu Sun Wei Zhang Department of Electrical and Computer Engineering Southern Illinois University Carbondale Carbondale

ISBN: (纸本)9781424449316

As a successful programming language, java has extended its application from general-purpose systems to embedded, real-time systems. However, some of java's excellent features, like automatic memory management and dynamic compilation, bring indeterminism to the execution time of real-time java programs. In this paper, we propose several multi-core approaches to remove or at least reduce the unpredictability inside of java virtual machine (JVM). Our goal is to retain high performance competitive to dynamic compilation and, at the same time, obtain better time predictability for JVM. Also, we study pre-compilation techniques to utilize second core more efficiently. Furthermore, we develop Pre-optimization on Another Core (PoAC) scheme to replace the Adaptive Optimization System (AOS) in Jikes JVM, which is very sensitive to execution time variation and impacts time predictability greatly. The experimental results indicate that our approaches are able to reach high performance while greatly reduce execution time variation of java applications.

关键词： Time predictability java virtual machine Multicore processors Adaptive optimizations

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Efficient exception handling in java bytecode-to-C ahead-of-time compiler for embedded systems

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COMPUTER LANGUAGES SYSTEMS & STRUCTURES 2008年第4期34卷 170-183页

作者： Jung, Dong-Heon Park, JongKuk Bae, Sung-Hwan Lee, Jaemok Moon, Soo-Mook Seoul Natl Univ Sch Elect Engn & Comp Sci Seoul 151742 South Korea

One of the most promising approaches to java acceleration in embedded systems is a bytecode-to-C ahead-of-time compiler (AOTC). It improves the performance of a java virtual machine (JVM) by translating bytecode into C code, which is then compiled into machine code via an existing C compiler. One important design issue in AOTC is efficient exception handling. Since the excepting point and the exception handier may locate in different methods on a call stack, control transfer between them should be streamlined, while an exception would be an "exceptional" event, so it should not slow down normal execution paths. Previous AOTCs often employed a technique called stack cutting based on a setjmp()/Iongjmp() pair, which we found is involved with too much performance overheads. Also, when the AOTC and the interpreter are employed concurrently (e.g., some methods are AOTCed while other methods are interpreted), the performance of normal execution paths is affected more seriously. This paper proposes a simpler solution based on an exception check after each method call, merged with garbage collection check for reducing its overhead. Our evaluation results on SPECjvm98 on Sun's CVM indicate that our technique can improve the performance of stack cutting by more than 25%. A similar performance benefit can be noted on a hybrid execution environment of both the AOTC and the interpreter. (C) 2007 Elsevier Ltd. All rights reserved.

关键词： bytecode-to-C java ahead-of-time compiler exception handling stack cutting java virtual machine J2ME CDC

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Mobile JikesRVM: A framework to support transparent java thread migration

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SCIENCE OF COMPUTER PROGRAMMING 2008年第2-3期70卷 221-240页

作者： Quitadamo, Raffaele Cabri, Giacomo Leonardi, Letizia Univ Modena & Reggio Emilia Dipartimento Ingn Informat I-41100 Modena Italy

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. (C) 2007 Elsevier B.V. All rights reserved.

关键词： java virtual machine thread migration code mobility JikesRVM distributed applications

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Designing highly flexible virtual machines: the JnJVM experience

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SOFTWARE-PRACTICE & EXPERIENCE 2008年第15期38卷 1643-1675页

作者： Thomas, Gael Geoffray, Nicolas Clement, Charles Folliot, Bertil Univ Paris 06 CNRS LIP6 INRIA REGAL F-75016 Paris France

Dynamic flexibility is a major challenge in modern system design to react to context or applicative requirements evolutions. Adapting behaviors may impose substantial code modification across the whole system, in the field, without service interruption and without state loss. This paper presents the JnJVM, a full java virtual machine (JVM) that satisfies these needs by using dynamic aspect weaving techniques and a component architecture. It supports adding or replacing its own code, while it is running, with no overhead on unmodified code execution. Our measurements reveal similar performance when compared with the monolithic JVM Kaffe. Three illustrative examples show different extension scenarios: (i) modifying the JVMs behavior;(ii) adding capabilities to the JVM;and (iii) modifying applications behavior. Copyright (C) 2008 John Wiley & Sons, Ltd.

关键词： dynamic adaptation aspect weaving java virtual machine

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Enhanced hot spot detection heuristics for embedded java just-in-time compilers

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ACM SIGPLAN NOTICES 2008年第7期43卷 13-22页

作者： Lee, Seong-Won Moon, Soo-Mook Kim, Seong-Moo Seoul Natl Univ Sch Elect Engn Seoul 151 South Korea

Most java just-in-time compilers (JITC) try to compile only hot methods since the compilation overhead is part of the running time. This requires precise and efficient hot spot detection, which includes distinguishing hot methods from cold methods, detecting them as early as possible, and paying a small runtime overhead for detection. A hot method could be identified by measuring its running time during interpretation since a long-running method is likely to be a hot method. However, precise measurement of the running time during execution is too expensive, especially in embedded systems, so many counter-based heuristics have been proposed to estimate it. The Simple heuristic counts only method invocations without any consideration of loops [1], while Sun's HotSpot heuristic counts loop iterations as well, but does not consider loop sizes or method sizes [2,14]. The static analysis heuristic estimates the running time of a method by statically analyzing loops or heavy-cost bytecodes but does not measure their dynamic counts [3]. Although the overhead of these heuristics is low, they do not estimate the running time precisely, which may lead to imprecise hot spot detection. This paper proposes a new hot spot detection heuristic which can estimate the running time more precisely than others with a relatively low overhead. It dynamically counts only important bytecodes interpreted, but with a simple arithmetic calculation it can obtain the precise count of all interpreted bytecodes. We also propose employing a static analysis technique to predict those hot methods which spend a huge execution time once invoked. This static prediction can allow compiling these methods at their first-invocation, complementing the proposed dynamic estimation technique. We implemented both, which led to a performance benefit of 10% compared to the HotSpot heuristic.

关键词： performance experimentation languages java just-in-time compilation hot spot detection Sun's HotSpot heuristic java virtual machine J2ME CDC

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Flexible task graphs: A unified restricted thread programming model for java

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ACM SIGPLAN NOTICES 2008年第7期43卷 1-11页

作者： Auerbach, Joshua Bacon, David F. Guerraoui, Rachid Spring, Jesper Honig Vitek, Jan IBM Res Yorktown Hts NY 10598 USA Ecole Polytech Fed Lausanne CH-1015 Lausanne Switzerland Purdue Univ Dept Comp Sci W Lafayette IN 47907 USA

The disadvantages of unconstrained shared-memory multi-threading in java, especially with regard to latency and determinism in real-time systems, have given rise to a variety of language extensions that place restrictions on how threads allocate, share, and communicate memory, leading to order-of-magnitude reductions in latency and jitter. However, each model makes different trade-offs with respect to expressiveness, efficiency, enforcement, and latency, and no one model is best for all applications. In this paper we present Flexible Task Graphs (Flexotasks), a single system that allows different isolation policies and mechanisms to be combined in an orthogonal manner, subsuming four previously proposed models as well as making it possible to use new combinations best suited to the needs of particular applications. We evaluate our implementation on top of the IBM Web-Sphere Real Time java virtual machine using both a microbenchmark and a 30 KLOC avionics collision detector. We show that Flexotasks are capable of executing periodic threads at 10 KHz with a standard deviation of 1.2 mu s and that it achieves significantly better performance than RTSJ's scoped memory constructs while remaining impervious to interference from global garbage collection.

关键词： languages experimentation real-time systems java virtual machine memory management ownership types

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Impact of JVM superoperators on energy consumption in resource-constrained embedded systems

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ACM SIGPLAN NOTICES 2008年第7期43卷 12-30页

作者： Badea, Carmen Nicolau, Alexandru Veidenbaum, Alexander V. Univ Calif Irvine Dept Comp Sci Ctr Embedded Comp Syst Irvine CA 92717 USA

Energy consumption is one of the most important issues in resource-constrained embedded systems. Many such systems run java-based applications due to java's architecture-independent format (bytecode). Standard techniques for executing bytecode programs, e. g. interpretation or just-in-time compilation, have performance or memory issues that make them unsuitable for resource-constrained embedded systems. A superoperator-extended, lightweight java virtual machine (JVM) can be used in resource-constrained embedded systems to improve performance and reduce memory consumption. This paper shows that such a JVM also significantly reduces energy consumption. This is due primarily to a considerable reduction in the number of memory accesses and thus in energy consumption in the instruction and data TLBs and caches and, in most cases, in DRAM energy consumption. Since the fraction of processor energy dissipated in these units is approximately 60%, the energy savings achieved are significant. The paper evaluates the number of load, store, and computational instructions eliminated by the use of proposed superoperators as compared to a simple interpreter on a set of embedded benchmarks. Using cache and DRAM per access energy we estimate the total processor/DRAM energy saved by using our JVM. Our results show that with 32KB caches the reduction in energy consumption ranges from 40% to 60% of the overall processor, plus DRAM energy. Even higher savings may be achieved with smaller caches and increased access to DRAM as DRAM access energy is fairly high.

关键词： experimentation measurement performance energy estimation java virtual machine superoperators profile-guided optimization embedded systems

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Application- and Transaction Isolation under java

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COMPUTER SCIENCE-RESEARCH AND DEVELOPMENT 2008年第2期22卷 59-69页

作者： Mueller, Jens Spruth, Wilhelm G. Univ Tubingen Wilhelm Schickard Inst Informat Arbeitsbereich Tech Informat Sand 13 D-72076 Tubingen Germany Univ Leipzig Inst Informat Abt Computersysteme D-04103 Leipzig Germany

The java Platform, Enterprise Edition (java EE, previous term: J2EE) has been designed to permit the use of java for mission critical transactional business applications such as financial accounting or enterprise resource planning systems. When programming such applications it is still difficult to assure the isolation between transactions executing in parallel. Compliance with transaction isolation is a basic requirement to keep underlying data in a consistent state. This paper analyses existing problems and gives an overview of the solutions that are presently available or under discussion.

关键词： ACID Application Isolation API Enterprise javaBeans Isolation J2EE java EE java virtual machine JSR 121 Multi Tasking virtual machine Persistent Reusable java virtual machine virtual machine Container Transaction

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