Fast, Interactive Worst-Case Execution Time Analysis With Back-Annotation

Abstract—For hard real-time systems, static code analysis is needed to derive a safe bound on the worst-case execution time (WCET). Virtually all prior work has focused on the accuracy of WCET analysis without regard to the speed of analysis. The resulting algorithms are often too slow to be integrated into the development cycle, requiring WCET analysis to be postponed until a final verification phase. In this paper we propose interactive WCET analysis as a new method to provide near-instantaneous WCET feedback to the developer during software programming. We show that interactive WCET analysis is feasible using tree-based WCET calculation. The feedback is realized with a plugin for the Java editor jEdit, where the WCET values are back-annotated to the Java source at the statement level. Comparison of this treebased approach with the implicit path enumeration technique (IPET) shows that tree-based analysis scales better with respect to program size and gives similar WCET values. Index Terms—Real time systems, performance analysis, software performance, software reliability, software algorithms, safety I

Toward libraries for real-time Java

“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.”Reusable libraries are problematic for real-time software in Java. Using Java's standard class library, for example, demands meticulous coding and testing to avoid response time spikes and garbage collection. We propose two design requirements for reusable libraries in real-time systems: worst-case execution time (WCET) bounds and worst- case memory consumption bounds. Furthermore, WCET cannot be known if blocking method calls are used. We have applied these requirements to the design of three Java-based prototypes: a set of collection classes, a networking stack, and trigonometric functions. Our prototypes show that reusable libraries can meet these requirements and thus be viable for real-time systems

A modular worst-case execution time analysis tool for Java processors

“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.”Recent technologies such as the Real-Time Specification for Java promise to bring Java's advantages to real-time systems. While these technologies have made Java more predictable, they lack a crucial element: support for determining the worst-case execution time (WCET). Without knowledge of WCET, the correct temporal behavior of a Java program cannot be guaranteed. Although considerable research has been applied to the theory of WCET analysis, implementations are much less common, particularly for Java. Recognizing this deficiency, we have created an opensource, extensible tool that supports WCET analysis of Java programs. Designed for flexibility, it is built around a plug-in model that allows features to be incorporated as needed. Users can plug in various processor models, loop bound detectors, and WCET analysis algorithms without having to understand or alter the tool's internals

Toward a unified standard for worst-case execution time annotations in real-time Java

As real-time systems become more prevalent, there is a need to guarantee that these increasingly complex systems perform as designed. One technique involves a static analysis to place an upper bound on worst-case execution time (WCET). This temporal analysis cannot be made automatic and normally requires source annotations to assist a WCET analysis tool. At the same time, there is a growing interest in using Java for real-time systems. Several WCET analysis prototypes for Java have been created, and more are under development. Each relies on a competing and incompatible convention for annotations, resulting in portability problems and duplication of effort. We propose that Java’s own annotation mechanism should be used to address such issues. These builtin annotations provide a common platform for WCET analysis, improving portability and reducing the effort necessary to create these vital tools. We examine the features that make Java’s annotation standard attractive for WCET analysis, then discuss its current failings and make recommendations for future improvements. 1

VADRE: A Visual Approach to Performance Analysis of Distributed, Real-time Systems

Distributed, real-time, and embedded (DRE) systems are becoming increasingly complex, and as a result, performance analysis of such systems is becoming increasingly difficult. Current profiling tools are ill-equipped to analyze DRE system performance, primarily due to the distributed nature of these systems. We have begun to address this problem by forging the first in a suite of tools that we call VADRE: Visual Analysis of Distributed, Real-time, and Embedded systems. Like a CAT scan for distributed systems, these tools will provide a simplified and highly visual means of inspecting and understanding a system's performance.To demonstrate the feasibility and potential benefits of VADRE, we have developed the first tool in the suite. Called Jango, it is specialized for the CORBA domain. It can automatically collect timing data from a CORBA-based distributed system and display a timeline of remote method calls. With input from the user, it can run a basic deadline checking algorithm, revealing precisely when and where a deadline is missed. This technique simplifies and quickens the process of testing a distributed system for adherence to real-time constraints. As a case study in validating the capabilities of Jango, we have applied it to a robotic DRE control system and discuss the results here

Automatic Performance Visualization of Distributed Real-time systems

For distributed real-time systems, adequate profiling tools are exceedingly rare. The sheer variety and low-level nature of these systems impede the adoption of standard, general-purpose tools for performance analysis and visualization. Although much research has been devoted to profiling parallel clusters and supercomputers, the literature virtually ignores the real-time domain. Correspondingly, a handful of commercial tools is available for profiling realtime software, but they invariably make a single-node assumption and are unable to cope with distributed environments. We examine the state of performance analysis and discuss why profilers are conspicuously absent in the field of distributed real-time systems. We then explore how developers of these systems could benefit from graphical profiling tools with automatic instrumentation and data collection. Toward that end, we demonstrate the prototype of a performance visualization tool called "Bacara", the second addition to our suite of tools for visual analysis of distributed real-time systems, or VADR

Late Demarshalling: A Technique for Efficient Multi-language Middleware for Embedded Systems

A major goal of middleware is to allow seamless software integration across programming languages. CORBA, for example, supports multiple languages by specifying communication standards and language-specific bindings. Although this approach works well for desktop systems, it is problematic for embedded systems, where strict memory limits discourage multiple middleware implementations.A common memory-efficient alternative allows sharing of middleware by exposing functionality through language-specific wrappers; for instance, middleware may be implemented in C++ but exposed to Java through the Java Native Interface (JNI). Like most language wrappers, however, JNI degrades performance, especially with aggregate data types.We present “late demarshalling”: a fast, memory-efficient technique for multi-language middleware. By passing arguments at the middleware message level as a packed stream and unpacking them after crossing the language boundary, we obtain both high performance and reduced memory footprint. We provide a proof-of-concept implementation for Java and C++ with measurements showing improved performance and footprint

Adaptive Techniques for Minimizing Middleware Memory Footprint for Distributed, Real-Time, Embedded Systems

In order for middleware to be widely useful for distributed, real-time, and embedded systems, it should provide a full set of services and be easily customizable to meet the memory footprint limitations of embedded systems. In this paper, we examine a variety of techniques used to reduce memory footprint in middleware. We found that combining aspect-oriented programming with code shrinkers and obfuscators reduces the memory footprint of CORBA middleware to <5% of its original size, as customized for a small client application for a memoryconstrained embedded device