High-level Language Virtual Machines Research Articles

Short-circuit dispatch

Interpreters are widely used to implement high-level language virtual machines (VMs), especially on resource-constrained embedded platforms. Many scripting languages employ interpreter-based VMs for their advantages over native code compilers, such as portability, smaller resource footprint, and compact codes. For efficient interpretation a script (program) is first compiled into an intermediate representation, or bytecodes . The canonical interpreter then runs an infinite loop that fetches, decodes, and executes one bytecode at a time. This bytecode dispatch loop is a well-known source of inefficiency, typically featuring a large jump table with a hard-to-predict indirect jump. Most existing techniques to optimize this loop focus on reducing the misprediction rate of this indirect jump in both hardware and software. However, these techniques are much less effective on embedded processors with shallow pipelines and low IPCs. Instead, we tackle another source of inefficiency more prominent on embedded platforms--redundant computation in the dispatch loop. To this end, we propose Short-Circuit Dispatch (SCD), a low-cost architectural extension that enables fast, hardware-based bytecode dispatch with fewer instructions. The key idea of SCD is to overlay the software-created bytecode jump table on a branch target buffer (BTB). Once a bytecode is fetched, the BTB is looked up using the bytecode, instead of PC, as key. If it hits, the interpreter directly jumps to the target address retrieved from the BTB; otherwise, it goes through the original dispatch path. This effectively eliminates redundant computation in the dispatcher code for decode, bound check, and target address calculation, thus significantly reducing total instruction count. Our simulation results demonstrate that SCD achieves geomean speedups of 19.9% and 14.1% for two production-grade script interpreters for Lua and JavaScript, respectively. Moreover, our fully synthesizable RTL design based on a RISC-V embedded processor shows that SCD improves the EDP of the Lua interpreter by 24.2%, while increasing the chip area by only 0.72% at a 40nm technology node.

Effect of Virtualization on Enterprise Network, Server/Desktop Systems on Small and Mid-Size Businesses (SMB)

INTRODUCTION Enterprise network infrastructure has profoundly impacted information systems business world. As small, mid-size businesses, various devices and data move beyond the traditional security of the corporate landscape, cyber-attacks will continue to grow at an exponential proportion. In 2012, network security gurus experienced cyber dangers ranging from sophisticated advanced persistent threats, to firewire attacks, to lost or stolen laptop. Enterprise network's mobile endpoints are literally moving targets and until they are adequately secured against attacks, enterprise business intelligence, reputation or competitiveness are at risk The goal of this article included the following: 1. To identify the extent mid- size organizations have adopted or planned to adopt virtualization technology 2012. 2. Identify potential barriers that cause enterprise systems to postpone or decide not to adopt virtualization. 3. Identify among adopting firms, what virtualization products are most popular and which applications are most commonly virtualized? 4. Identify the core drivers that cause enterprise systems to be virtualized. LITERATURE REVIEW Berde et al. (2009) among others noted that virtualization is not a perfect solution to how organizations manage their resources but concluded that this technology provides tremendous capabilities on how enterprise systems manage and move operating systems into different hardware resources. Grid computing evolved as an innovative technology, and is distinguished from traditional distributed networks because of its large-scale resource sharing capabilities. The author further explained that grid computing allows large numbers of hardware components to act as a single device, thereby, pooling their capacity and re-allocating these components to different jobs. Ercan (2010) argued that in the next generation of Grids, applications will not necessarily be designed to run on certain piece of hardware or network, but will be written to consume certain types of resources, which could be provided anywhere on the network. He further summarized that to accomplish this, enterprise systems and technical gurus need more dynamic networks than are at the present time existence. However, noted that virtualization efforts the networking community are already moving the industry that direction. Fiedler and Gallenkamp (2008), their study reviled that virtualized infrastructure provides a layer of abstraction between computing storage, networking hardware, and the applications running on it. Their study further explained that the deployment of virtual infrastructure is nondisruptive to the system, because the user experiences are typically un-noticed or unchanged. The authors concludes by emphasizing that virtual infrastructure provide enterprise system management, the opportunity to manage pooled resources across the enterprise, thereby, allowing Information Technology (IT) managers to be more responsive to dynamic system needs to better leverage infrastructure investments. Early studies by Burry et al. (2004), Brandel (2004), Cannor (2005), found evidence that virtualization has been a part of the IT landscape for decades but today vendors are now conveying remuneration to industry-standard X86-based platforms which now encompass the preponderance of desktops, laptops and server shipments. They concluded by stating that a major benefit of virtualization is the ability of systems to run multiple operating systems on a single physical system while sharing the underlying hardware resources or partitioning. More recent studies have concluded that virtualization can apply to a range of system layers, including hardware-level virtualization, operating system- level virtualization, and high-level language virtual machines (Morana et al., 2011; Seyler et al., 2011; Tusa & Mikkilinemi, 2011) . …

CSOM/PL — A Virtual Machine Product Line.

CSOM/PL is a software product line (SPL) derived from apply- ing multi-dimensional separation of concerns (MDSOC) techniques to the domain of high-level language virtual machine (VM) implementations. For CSOM/PL, we modularised CSOM, a Smalltalk VM implemented in C, using VMADL (virtual machine architecture description language). Several features of the original CSOM were encapsulated in VMADL modules and composed in various combinations. In an evaluation of our approach, we show that applying MDSOC and SPL principles to a domain as complex as that of VMs is not only feasible but beneficial, as it improves under- standability, maintainability, and configurability of VM implementations without harming performance.

Virtual Machine Support for Many-Core Architectures: Decoupling Abstract from Concrete Concurrency Models

The upcoming many-core architectures require software developers to exploit concurrency to utilize available computational power. Today's high-level language virtual machines (VMs), which are a cornerstone of software development, do not provide sufficient abstraction for concurrency concepts. We analyze concrete and abstract concurrency models and identify the challenges they impose for VMs. To provide sufficient concurrency support in VMs, we propose to integrate concurrency operations into VM instruction sets. Since there will always be VMs optimized for special purposes, our goal is to develop a methodology to design instruction sets with concurrency support. Therefore, we also propose a list of trade-offs that have to be investigated to advise the design of such instruction sets. As a first experiment, we implemented one instruction set extension for shared memory and one for non-shared memory concurrency. From our experimental results, we derived a list of requirements for a full-grown experimental environment for further research.

Javana

Understanding the behavior of applications running on high-level language virtual machines, as is the case in Java, is non-trivial because of the tight entanglement at the lowest execution level between the application and the virtual machine. This paper proposes Javana, a system for building Java program analysis tools. Javana provides an easy-to-use instrumentation infrastructure that allows for building customized profiling tools very quickly.Javana runs a dynamic binary instrumentation tool underneath the virtual machine. The virtual machine communicates with the instrumentation layer through an event handling mechanism for building a vertical map that links low-level native instruction pointers and memory addresses to high-level language concepts such as objects, methods, threads, lines of code, etc. The dynamic binary instrumentation tool then intercepts all memory accesses and instructions executed and provides the Javana end user with high-level language information for all memory accesses and natively executed instructions.We demonstrate the power of Javana through a number of applications: memory address tracing, vertical cache simulation and object lifetime computation. For each of these applications, the instrumentation specification requires only a small number of lines of code. Developing similarly powerful profiling tools within a virtual machine (as done in current practice) is both time-consuming and error-prone; in addition, the accuracy of the obtained profiling results might be questionable as we show in this paper.