Jalapeño is a virtual machine for Java TM servers written in the Java language. To be able to address the requirements of servers (performance and scalability in particular), Jalapeño was designed "from scratch" to be as self-sufficient as possible. Jalapeño's unique object model and memory layout allows a hardware null-pointer check as well as fast access to array elements, fields, and methods. Run-time services conventionally provided in native code are implemented primarily in Java. Java threads are multiplexed by virtual processors (implemented as operating system threads). A family of concurrent object allocators and parallel type-accurate garbage collectors is supported. Jalapeño's interoperable compilers enable quasi-preemptive thread switching and precise location of object references. Jalapeño's dynamic optimizing compiler is designed to obtain high quality code for methods that are observed to be frequently executed or computationally intensive.
This paper describes the evolution of the Jikese Research Virtual Machine project from an IBM internal research project, called Jalapeñ o, into an open-source project. After summarizing the original goals of the project, we discuss the motivation for releasing it as an open-source project and the activities performed to ensure the success of the project. Throughout, we highlight the unique challenges of developing and maintaining an open-source project designed specifically to support a research community. On October 15, 2001, IBM Research launched the Jikes* RVM (Research Virtual Machine) open-source project.Jikes RVM provides a novel virtual-machine software infrastructure, suitable for research on modern programming language design and implementation techniques. Over the past three years, the project has grown and made a significant impact on the programming-language research community. This paper describes the evolution of Jikes RVM from an IBM internal research project, called Jalapeñ o, into a full-fledged open-source project. The story provides an instructive case study on how a small systems research project can grow into a shared project used by hundreds of researchers. The paper discusses a variety of challenges that arose in this process, including the technical enhancements and software-engineering practices needed to ensure the project's success; dealing with intellectual property, corporate process, and licensing issues;promoting the system in the research community; and developing a community to maintain and enhance the system in the future.The primary focus of the Jikes RVM project was the development of a software platform designed to be a research testbed for the prototyping of new technologies. In contrast, most open-source projects develop software products for use by the general public. We focus on the implications of this distinction throughout the paper.The remainder of this paper is as follows. The next section begins with a general discussion of issues Ó
A parameterized generic model that captures the features of diverse computer architectures would facilitate the development of portable programs. Specific models appropriate to particular computers are obtained by Specifying parameters of the generic model. A generic model should be simple, and for each machine that it is intended t o represent, it should have a reasonably accurate specific model.
The Parallel Memory Hierarchy (PMH) model of computation uses a single mechanism to model the costs of both interprocessor communication and memory hierarchy trafic. A computer is modeled as a treeof memory modules with processors at the leaves. All data movement takes the f o r m of block transfers between children and their parents. This paper assesses the strengths and weaknesses of the PMH model as a generic model.
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