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

Gerçek zamanlı Java’ da büyük nesnelere bellek ayırmak için anahtarlamalı yaklaşım

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Son yirmi yılda nesne yönelimli programlama dilleri ve yönetilen çalışma zamanları, yazılım mühendisliği yönünden sağladıkları avantajlardan ötürü oldukça popüler hale geldiler. Ancak birçok uygulama alanındaki bu popülerliklerinin aksine, aynı programlama dilleri ve çalışma zamanları, gerçek zamanlı programlama için uygun görülmediler. Birçok faktörün yanı sıra, bunların gerçek zamanlı sistemlerin geliştirilmesi için kullanılmalarının önündeki bariyerlerden bir tanesi, büyük nesnelere bellek ayırma esnasında karşılaşılma olasılığı olan uzun bekleme zamanlarıdır. Bu tez gerçek zamanlı Java için zamanımıza kadar geliştirilmiş olan farklı büyük nesnelere bellek ayırma çözümlerini inceler ve bu çözümlere alternatif olarak anahtarlamalı yeni bir yaklaşım sunar. Sunulan tekniğin performansının hali hazırda uygulanmış diğer tekniklerle karşılaştırılması amacıyla geliştirilmiş olan sentetik bir kıyaslama uygulaması da bu tezde açıklanmıştır.Over the last twenty years object oriented programming languages and managed runtimes like Java have been very popular because of their software engineering benefits. Despite their popularity in many application areas, they have not been considered suitable for real-time programming. Besides many other factors, one of the barriers that prevent their acceptance in the development of real-time systems is the long pause times that may arise during large object allocation. This thesis examines different kinds of solutions which have been developed so far and introduces a switchable approach to large object allocation in real-time Java. A synthetic benchmark application which is developed to evaluate the effectiveness of the presented technique against other currently implemented techniques is also described

Gerçek zamanlı Java’ da büyük nesnelere bellek ayırmak için anahtarlamalı yaklaşım

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Son yirmi yılda nesne yönelimli programlama dilleri ve yönetilen çalışma zamanları, yazılım mühendisliği yönünden sağladıkları avantajlardan ötürü oldukça popüler hale geldiler. Ancak birçok uygulama alanındaki bu popülerliklerinin aksine, aynı programlama dilleri ve çalışma zamanları, gerçek zamanlı programlama için uygun görülmediler. Birçok faktörün yanı sıra, bunların gerçek zamanlı sistemlerin geliştirilmesi için kullanılmalarının önündeki bariyerlerden bir tanesi, büyük nesnelere bellek ayırma esnasında karşılaşılma olasılığı olan uzun bekleme zamanlarıdır. Bu tez gerçek zamanlı Java için zamanımıza kadar geliştirilmiş olan farklı büyük nesnelere bellek ayırma çözümlerini inceler ve bu çözümlere alternatif olarak anahtarlamalı yeni bir yaklaşım sunar. Sunulan tekniğin performansının hali hazırda uygulanmış diğer tekniklerle karşılaştırılması amacıyla geliştirilmiş olan sentetik bir kıyaslama uygulaması da bu tezde açıklanmıştır.Over the last twenty years object oriented programming languages and managed runtimes like Java have been very popular because of their software engineering benefits. Despite their popularity in many application areas, they have not been considered suitable for real-time programming. Besides many other factors, one of the barriers that prevent their acceptance in the development of real-time systems is the long pause times that may arise during large object allocation. This thesis examines different kinds of solutions which have been developed so far and introduces a switchable approach to large object allocation in real-time Java. A synthetic benchmark application which is developed to evaluate the effectiveness of the presented technique against other currently implemented techniques is also described

Optimizing scoped and immortal memory management in real-time java

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The Real-Time Specification for Java (RTSJ) introduces a new memory management model which avoids interfering with the garbage collection process and achieves better deterministic behaviour. In addition to the heap memory, two types of memory areas are provided - immortal and scoped. The research presented in this Thesis aims to optimize the use of the scoped and immortal memory model in RTSJ applications. Firstly, it provides an empirical study of the impact of scoped memory on execution time and memory consumption with different data objects allocated in scoped memory areas. It highlights different characteristics for the scoped memory model related to one of the RTSJ implementations (SUN RTS 2.2). Secondly, a new RTSJ case study which integrates scoped and immortal memory techniques to apply different memory models is presented. A simulation tool for a real-time Java application is developed which is the first in the literature that shows scoped memory and immortal memory consumption of an RTSJ application over a period of time. The simulation tool helps developers to choose the most appropriate scoped memory model by monitoring memory consumption and application execution time. The simulation demonstrates that a developer is able to compare and choose the most appropriate scoped memory design model that achieves the least memory footprint. Results showed that the memory design model with a higher number of scopes achieved the least memory footprint. However, the number of scopes per se does not always indicate a satisfactory memory footprint; choosing the right objects/threads to be allocated into scopes is an important factor to be considered. Recommendations and guidelines for developing RTSJ applications which use a scoped memory model are also provided. Finally, monitoring scoped and immortal memory at runtime may help in catching possible memory leaks. The case study with the simulation tool developed showed a space overhead incurred by immortal memory. In this research, dynamic code slicing is also employed as a debugging technique to explore constant increases in immortal memory. Two programming design patterns are presented for decreasing immortal memory overheads generated by specific data structures. Experimental results showed a significant decrease in immortal memory consumption at runtime

Specification And Runtime Checking Of Timing Constraints In Safety Critical Java

The Java platform is becoming a vital tool for developing real-time and safety-critical systems. Design patterns and the availability of Java libraries, both provide solutions to many known problems. Furthermore, the object-oriented nature of Java simplifies modular development of real-time systems. However, limitations of Java as a programming language for real-time systems are a notable obstacle to producing safe real-time systems. These limitations are found in the unpredictable execution model of the language, due to Java’s garbage collector, and the lack of support for non-functional specification and verification tools. In this dissertation I introduce SafeJML, a specification language for support of functional and non-functional specifications, based on an implementation of a safety-critical Java platform and the Java Modeling Language (JML). This dissertation concentrates on techniques that enable specification and dynamic checking of timing constraints for some important Java features, including methods and subtyping. SafeJML and these dynamic checking techniques allow modular specification and checking of safety-critical systems, including those that use object-orientation and design patterns. Such coding techniques could have maintenance benefits for real-time and safety-critical softwar

Design and Implementation of a Comprehensive Real-time Java Virtual Machine

The emergence of standards for programming real-time systems in Java has encouraged many developers to consider its use for systems previously only built using C, Ada, or assembly language. However, the RTSJ standard in isolation leaves many important problems unaddressed, and suffers from some serious problems in usability and safety. As a result, the use of Java for real-time programming has continued to be viewed as risky and adoption has been slow. In this paper we provide a description of IBM’s new real-time Java virtual machine product, which combines Metronome realtime garbage collection, ahead-of-time compilation, and a complete implementation of the RTSJ standard, running on top of a custom real-time multiprocessor Linux kernel. We will describe the implementation of each of these components, including how they interacted both positively and negatively, and the extensions to previous work required to move it from research prototype to a system implementing the complete semantics of the Java language. The system has been adopted for hard real-time development of naval weapons systems and soft real-time telecommunications servers. We present measurements showing that the system is able to provide sub-millisecond worst-case garbage collection latencies, 50 microsecond Linux scheduling accuracy, and eliminate non-determinism due to JIT compilation