Modernizing the Real-Time and Embedded Curriculum

Transcription

1 Modernizing the Real-Time and Embedded Curriculum Kelvin Nilsen, Ph.D. Chief Technology Officer Java, Atego Systems, Inc Cornerstone Court West, Suite 250, San Diego, CA 92121, USA Abstract - Traditionally, real-time and embedded software design and implementation has been the purview of computer engineering departments. A course dedicated to these topics, if it is offered at all, is often accompanied by aspects of hardware design and hardware device interfaces. Programming assignments usually use C or assembly language. This paper argues that traditional approaches to educating real-time and embedded engineers are outdated and fail to prepare students for typical modern real-time software engineering challenges. Modern embedded real-time systems are very different than the embedded real-time systems of 20 ago. Among trends that have not been addressed in the typical embedded real-time curriculum are first, a tremendous increase in size and complexity of embedded system software, with many systems doubling in size with each new product release, typically occuring every 18 to 36 months; second, a tendency to build each new product release primarily by integration of existing software components rather than by implementing all of the functionality for the new product from scratch; and third, the reality that reusable embedded and real-time software components are required to provide multiple decades of service on a rapidly evolving assortment of hardware and operating system platforms. Keywords: Real-Time Java, Embedded Real-Time, Curriculum 1 Current Industry Practice While it is still the case that a large number of embedded systems are still programmed in C and assembler, it is also true that increasingly, embedded real-time systems are being implemented in more modern object-oriented programming languages like Java [1]. Note, for example, that the highly popular Android platform uses Java as its preferred programming language [2]. Real-time Java has been used in the implementations of critical telecommunications infrastructure, manufacturing of semiconductors, automation of off-shore oil drilling rigs, multiple RADAR applications, situational awareness tools for military infantry, and Aegis warship weapons control including ballistic missile defense software [3-7]. The motivations for the increased use of Java in the implementation of embedded real-time software systems are several fold. 1. Typical development projects find that Java offers a two-fold gain in developer productivity and five- to ten-fold cost savings during software integration and maintenance activities in comparison with legacy languages like C and C++ [8]. 2. The size of embedded software systems is growing exponentially, in close correlation with Moore s law. This is exhibited in Figure 1, which reports trends in NASA space mission software [9]. Similar trends have been reported by the consumer electronics and automotive software industries [10]. 3. While computer processing speeds and memory capacities continue to increase while the costs of computing resources are declining, the costs of software engineers continue to rise. This motivates tradeoffs that allow software engineers to be more productive at the expense of slightly less efficient use of computing resources. 4. Whereas the embedded software systems of past decades were small enough that one or two programmers could implement all of the code for each new device in less than a year of development, today s embedded systems are far too large and complex to support that model. The typical difference between last year s product and next year s product is a doubling of code size, from maybe 1 million lines of code to 2 million lines of code! All of the new code, most of which is supplied as reusable software components by third parties, must integrate cleanly with code deployed in the prior product release and with all of the other components to be added to the new product release. Some representative real-time Java applications are described in Table 1. Because these applications represent competitive advantages to their developers, certain details are omitted from some of the descriptions, as marked with the Ψ symbol.

2 Figure 1. Significant Lines of Code in NASA Space Mission Control Software Fleet Telematics Domain Size Periods Semiconductor Manufacturing ~6 man thousands of control points 100 ms 1 ms Off Shore Drilling Rigs Ψ 10 ms Power Plant Automation Helmet Mounted Situational Awareness for Foot Soldiers In-Flight Entertainment System Multi-Protocol Broadband Loop Carrier Long Haul Fiber Optic Telecommunications Switch Warship Weapons Control and Ballistic Missile Defense thousands of control points tens of man tens of man ~10 man ~100 man 500K SLOC Table 1. Sample Real-Time Java Applications 16.7 ms Ψ 100 ms Ψ 40 ms sub-ms 2 Relevant Trends in Computer Science Education In the 90s, the language of choice for most undergraduate Computer Science courses was C. Following its public release in 1996, Java has gradually taken over the role of dominant programming language for university instruction [11, 12]. Professors have found that the use of Java allows students to explore more interesting topics with less low-quality time spent by students, professors, and teaching assistants in lengthy debugging sessions. As a higher level language, Java completely eliminates the core dumps that frequently result from pointer arithmetic errors, array subscripting errors, the dereferencing of null and dangling pointers, and inappropriate type coercions. Furthermore, the choice to use Java allows instructors to expose students to good object-oriented practice as one of the side benefits of each class room assignment. This is important because object orientation is one of the key mechanisms used by industry to manage the complexity of today s ever increasing software system sizes. Being familiar with object-oriented principles and techniques helps graduating students find employment. 3 Suggested Embedded Real-Time Curriculum Outline The official curriculum recommendations for an elective course on embedded and real-time software

3 reflect biases that were most appropriate in prior decades, when all of the software for each embedded real-time device could be written from scratch by one or two programmers in less than a year. Only four topics are suggested for the course [13]: 1. Process and task scheduling 2. Memory/disk management requirements in a real-time environment 3. Failures, risks, and recovery 4. Special concerns in real-time systems This official list of topics leaves room for interpretation, allowing instructors to exercise discretion in choosing which special concerns in real-time systems they might want to include in the course. The reality is that if a course chooses to focus on the implementation of process and task scheduling and memory and disk management, there may be little time available to focus on topics relevant to the development of real-time applications. The outline of topics provided below aims to educate students in general principles of real-time application development. While many real-world development efforts may choose not to use a high-level programming language, the principles learned in this class are for the most part relevant to all real-time development, regardless of language. The choice to use a high-level programming language for course assignments allows more interesting topics to be studied in greater depth. 1. Rate monotonic scheduling theory: An important question that must be addressed in developing a real-time application is how to analyze the workload to prove that all tasks will satisfy their real-time constraints. While many real-time scheduling theories exist, we recommend that an introductory course present rate monotonic theory, as it is the most widely used analysis technique and is relatively easy to understand. 2. Empirical analysis of time and memory requirements for real-time tasks: In order to apply schedulability analysis, it is necessary to understand the CPU time consumed by all of the tasks in the workload. This is computed as the product of worst-case task execution times and task execution frequencies. Assuring reliable operation of a real-time workload also depends on an awareness of the memory consumption of all workload tasks. 3. Encapsulation of real-time attributes in reusable object-oriented real-time software components: Modern real-time systems are constructed out of the integration of many independently developed software components. Over the lifetime of a real-time software component, it will most likely be deployed in many different contexts, on a variety of different processors and real-time operating systems. To facilitate easy porting and integration of a real-time software component, bundle each component with the ability to analyze and report its CPU time and memory requirements. Note that a component s resource requirements may be different within each execution environment. 4. Account for infrastructure activities in analysis of real-time workload: The complete system workload typically includes certain infrastructure services that are acting on behalf of the application. Typical infrastructure services include implementations of solid state and/or magnetic disk drivers, network libraries, messaging services, and, when appropriate, real-time garbage collection of dead memory. 5. Comply with regulatory agency guidelines: Certain embedded real-time applications must satisfy regulatory auditors prior to commercial deployment. This is especially true of safety critical applications, such as commercial aircraft avionics systems and rail transport automation. Discuss software process requirements, accumulation of artifacts to document and support audits of software process, peer review of intermediate artifacts, legal accountability, and testing methodologies. 6. Distinguish hard real-time from soft real-time: Help students understand that hard real-time systems are never allowed to miss deadlines, whereas soft real-time systems are designed to be robust in the face of occasional missed deadlines. Construction of hard real-time systems depends on formal analysis of worst-case resource needs. Construction of soft real-time systems usually relies on empirical measurements and statistical analysis to quantify likelihoods of compliance with real-time constraints. The domain of hard real-time techniques is usually small and simple repetitive algorithms. The domain of soft realtime methodologies often includes workloads that are highly dynamic and may include complex algorithms and heuristic approximations. 7. Object-oriented techniques for hard real-time development: Traditional object-oriented programming depends on practices that are difficult to analyze to the levels of rigor generally required in hard real-time systems. Discuss techniques to reduce and discipline polymorphic method invocations. Explore technologies that replace dependency on automatic garbage collection with safe stack allocation.

4 4 Suggested Curriculum Implementation The recommended course structure relies on the use of real-time Java as the preferred foundation for course programming assignments. The reason is simple. Using Java for programming maximizes the learning experience while minimizing time spent in less productive peripheral pursuits. Furthermore, the use of Java offers improved coordination with other classes in the typical core curriculum of many computer science and software engineering programs. Several anecdotes from industry experience help emphasize these benefits. 1. Calix, an industry leading vendor of broadband loop carriers to bring DSL connections into homes and small offices, chose to replace their C implementation of the management plane software with a Java implementation. They found that they were able to write the Java version of this software in half the time required to implement the C version. Furthermore, they found that the Java version had fewer bugs and more features. This represents a two fold improvement in developer productivity. 2. Intel found that they were able to construct a fault tolerant demonstration of new hardware by integrating off-the-shelf Java software components in only three days of effort. They reported that previous efforts to do build similar demonstrations out of off-the-shelf C and C++ components required three sold months of developmenet effort. This represents a twenty fold improvement in developer productivity. 3. Lockheed Martin reports that they were able to verify 3,500 requirements for a portion of the Java implementation of the Aegis warship software in only 5 months. With the previous version of the Aegis software, which had been written in Ada and CMS-2 (proprietary military language), their experience had been to verify only 3-4 requirements per day. This represents a nine fold improvement. 4. After rewriting the Aegis weapons system software in Java, Lockheed Martin found they were able to add support for Standard Missile 6 in only 3 months of additional effort. Before the Java rewrite, they report that this activity would have required a full year of development. These productivity benefits result because Java offers higher levels of abstraction, improved separation of concerns through better encapsulation of software components, and superior portability. This has made it easier to integrate 3rd party library components from external sources, easier to reuse software components originally developed and tested on different platforms, and easier to test and verify software functionality on fast, large-memory server machines instead of on the slow, memory constrained devices that are typical of embedded deployments. In a university instructional setting, it means a class on principles of embedded real-time software development does not need to set aside and staff a special instructional laboratory for embedded real-time computing. Real-time Java technologies run on mainstream platforms like Linux and Windows as well. The jitter (unpredictable timing due to interference from other tasks) will of course be higher on a multi-user platform that is not designed to support real-time operation. Take this into consideration in establishing expectations for real-time determinsm. For an enrichment activity, it is always interesting to see the Java code developed and tested on a shared server downloaded and executed on a dedicated single board computer. There are many such boards available now which are directly supported by off-theshelf configurations of Linux and real-time Java virtual machines. Such boards are available today for under $150 [14], making it much easier today than in previous decades to experiment with true embedded systems development. Realize, however, that including embedded development and integration activities significantly reduces the time available in a one-semester course to study topics in real-time application development. To do both embedded and real-time topics justice, it is probably best to offer two courses, one focused on real-time application development, and the other focused on embedded device development. Exercises in hard realtime development and device driver implementation probably fit best within the embedded course. 5 A Call to Action This paper presents overview recommendations for changes in the embedded real-time curriculum. Developing these ideas into an off-the-shelf class requires significant effort. One of the reasons that embedded real-time development is not typically taught, or if taught, promotes outdated technologies and approaches, is because existing faculty are not generally familiar with the special needs of these industries. To make this course a reality at multiple universities, the following materials need to be developed: 1. A textbook needs to be available to cover the theory and principles of these topics. Currently, there does not exist a single textbook that covers all of the relevant topics. The textbook needs exercises and solutions to reinforce the learning planned for each topic.

5 2. A set of programming assignments needs to be developed along with sample solutions to each assignment. Supporting infrastructure software must be developed and provided to students so that they can focus their attention on the intended learning experience of each assignment without spending large amounts of time establishing the foundations on which their learning experience is to be based. A breakdown of principles to be reinforced and emphasized by each assignment should be provided. Programming assignments must align with classroom learning objectives. 3. A turnkey programming environment must be provided to make it easy for instructors to manage homework assignments. It must be easy to install and maintain this programming environment on readily available instructional computing platforms without adding significantly to the instructional lab staff s support burdens. While the author of this paper is willing to contribute to creation of course materials, the nature of his responsibilities in supporting commercial customers does not leave time to effectively prepare the classroom materials by himself. A collaborative effort between industry practitioners and professional educators would be ideal. An expression of interest in this curriculum development from multiple educational institutions would help multiple individuals to justify their contributions to the overall effort. 6 Summary The typical university treatment of embedded real-time development represents market requirements that are decades old. More modern real-time and embedded application development requires an understanding of principles and technologies that are not addressed in typical undergraduate or graduate programs in computer science and engineering. Suggested improvements to the embedded real-time curriculum would allow coursework to correlate better with current industry needs. 7 References [1] K. Arnold, J. Gosling, D. Holmes. The Java Programming Language, 4th edition. 928 pages. Prentice Hall PTR. Aug, [2] Jeff Friesen. Learn Java for Android Development. 656 pages. Apress. Sep. 29, [3] Calix Success Story, Atego white paper. 2 pages. May PERC_CalixSuccess_e.pdf [4] Nortel Success Story, Atego white paper. 3 pages. Oct PERC_NortelSuccess_e.pdf [5] National Oilwell Varco Selects Aonix PERC for Java-based Robotic Drilling, RigZone. Sept. 25, available at news/article.asp?a_id=36470 [6] Andrew Winkler. The Modernization of the Aegis Fleet with Open Architecture. Keynote talk, Java Technologies Real-Time and Embedded Systems. York, UK. Sept. 28, [7] Atego Press Release: Thales Air Systems Selects Aonix PERC Ultra for Execution on Ground Radar Systems, Mar. 03, [8] K. Nilsen. Applying COTS Java Benefits to Mission-Critical Real-Time Software, Crosstalk: The Journal of Defense Software Engineering. pp June [9] R. Lutz. Software Engineering for Space Exploration, IEEE Computer, pp vol. 44, no. 10 (Oct. 2011). [10] R. McMillan, GM CTO Sees More Code on Future Cars, Computer World, Oct. 20, [11] E. Roberts. Resources to Support the Use of Java in Introductory Computer Science, ACM SIGCSE 04, Norfolk, Virginia, USA. March 3-7, [12] E. Roberts, K. Bruce, R. Cutler, J. Cross, S. Grissom, K. Klee, S. Rodger, F. Trees, I. Utting, F. Yellin. The ACM Java Task Force Project Rationale. 118 pages. Aug [13] Computer Science Curriculum 2008: An Interim Revision of CS 2001, Dec Endorsed by ACM Education Council, Nov Endorsed by IEEE Computer Society Educational Activities Board, Nov. 16, [14] Mitch Frazier, The BeagleBoard: $149 Linux System, The Linux Journal, Aug 6, linux-system