Hideyuki Tokuda

Bio: Hideyuki Tokuda is an academic researcher from Keio University. The author has contributed to research in topics: Scheduling (computing) & Ubiquitous computing. The author has an hindex of 28, co-authored 53 publications receiving 3209 citations. Previous affiliations of Hideyuki Tokuda include Carnegie Mellon University.

A Time-Driven Scheduling Model for Real-Time Operating Systems.

Abstract: Process scheduling in real-time systems has almost invariably used one or more of three algorithms: fixed priority, FIFO, or round robin. The reasons for these choices are simplicity and speed in the operating system, but the cost to the system in terms of reliability and maintainability have not generally been assessed. This paper originates from the notion that the primary distinguishing characteristic of a real-time system is the concept that completion of a process or a set of processes has a value to the system which can be expressed as a function of time. This notion is described in terms of a time-driven scheduling model for real-time operating systems and provides a tool for measuring the effectiveness of most of the currently used process schedulers in real-time systems. Applying this model, we have constructed a multiprocessor real-time system simulator with which we measure a number of well-known scheduling algorithms such as Shortest Process Time (SPT), Deadline, Shortest Slack Time, FIFO, and a fixed priority scheduler, with respect to the resulting total system values. This approach to measuring the process scheduling effectiveness is a first step in our longer term effort to produce a scheduler which will explicitly schedule real-time processes in such a way that their execution times maximize their collective value to the system, either in a shared memory multiprocessing environment or in multiple nodes of a distributed processing environment.

Real-Time Mach: Towards a Predictable Real-Time System.

Abstract: Distributed real-time systems play a very important role in our modern society. They are used in aircraft control, communication systems, military command and control systems, factory automation, and robotics. However, satisfying the rigid timing requirements of various real-time activities in distributed real-time systems often requires ad hoc methods to tune the system’s runtime behavior The objective of Real-Time Mach is to develop a real-time version of the Mach kernel which provides users with a predictable and reliable distributed real-time computing environment. In this paper, we describe a real-time thread model, real-time synchronization, and the ITDS scheduler in RealTime Mach. We also discuss the implementation issues, a real-time toolset, and the current status of the system.

Is it still possible to extend TCP

Abstract: We've known for a while that the Internet has ossified as a result of the race to optimize existing applications or enhance security. NATs, performance-enhancing-proxies,firewalls and traffic normalizers are only a few of the middleboxes that are deployed in the network and look beyond the IP header to do their job. IP itself can't be extended because "IP options are not an option". Is the same true for TCP?In this paper we develop a measurement methodology for evaluating middlebox behavior relating to TCP extensions and present the results of measurements conducted from multiple vantage points. The short answer is that we can still extend TCP, but extensions' design is very constrained as it needs to take into account prevalent middlebox behaviors. For instance, absolute sequence numbers cannot be embedded in options, as middleboxes can rewrite ISN and preserve undefined options. Sequence numbering also must be consistent for a TCP connection, because many middleboxes only allow through contiguous flows.We used these findings to analyze three proposed extensions to TCP. We find that MPTCP is likely to work correctly in the Internet or fallback to regular TCP. TcpCrypt seems ready to be deployed, however it is fragile if resegmentation does happen---for instance with hardware offload. Finally, TCP extended options in its current form is not safe to deploy.

ARTS: a distributed real-time kernel

Abstract: ARTS is a distributed real-time operating system designed for a real-time systems testbed being developed at Camegle Mellon University. The objective of the testbed is to develop and verify advanced real-time computing technologies for a distributed environment. The tastbed consists of a set of SUN3 workstations connected by a real-time network based on IEEE 802.5 Token Ring and Ethernet. The goal of the ARTS Kernel is not to produce simply a fast real-time executive, but rather to provide users with a predictable, analyzable, and reliable distributed real-time computing environment. In particular, we have developed a real-time object model which is incorporated with a time fence protocol. The time fence protocol is used at every invocation in the object to detect the origin of timing errors. We also developed an integrated time-driven scheduling model and its scheduler based on the notion of policy/mechanism separation. Since each scheduling policy is implemented as a kernel object, a user can easily add policies or change the system's scheduling policy. A real-time toolset was also developed in order to predict the schedulability of the real-time activities.In this paper, we give an overview of the ARTS Kernel and ARTS real-time toolset. In particular, we introduce a real-time object model and the integrated time-driven scheduling model. We then describe the basic primitives and major components of the ARTS Kernel and the real-time toolset which consists of the schedulability analyzer, Scheduler 1-2-3, and the real-time monitor/debugger, ARM.

Processor Capacity Reserves for Multimedia Operating Systems

Abstract: Multimedia applications have timing requirements that cannot generally be satisfied using time-sharing scheduling algorithms and system structures. To effectively support these types of programs, operating systems must support processor capacity reservation. A capacity reservation and enforcement mechanism isolates programs from the timing and execution characteristics of other programs in the same way that a memory protection system isolates programs from memory access by other programs. In this paper, we characterize the timing requirements and processor capacity reservation requirements for multimedia applications, we describe a scheduling framework to support reservation and admission control, and we introduce a novel reserve abstraction, specifically designed for the microkernel architecture, for controlling processor usage.

A data-oriented (and beyond) network architecture

Abstract: The Internet has evolved greatly from its original incarnation. For instance, the vast majority of current Internet usage is data retrieval and service access, whereas the architecture was designed around host-to-host applications such as telnet and ftp. Moreover, the original Internet was a purely transparent carrier of packets, but now the various network stakeholders use middleboxes to improve security and accelerate applications. To adapt to these changes, we propose the Data-Oriented Network Architecture (DONA), which involves a clean-slate redesign of Internet naming and name resolution.

The Real-Time Specification for Java

Abstract: New languages, programming disciplines, operating systems, and software engineering techniques sometimes hold considerable potential for real-time software developers. A promising area of interest-but one fairly new to the real-time community-is object-oriented programming. Java, for example, draws heavily from object orientation and is highly suitable for extension to real-time and embedded systems. Recognizing this fit between Java and real-time software development, the Real-Time for Java Experts Group (RTJEG) began developing the real-time specification for Java (RTSJ) in March 1999 under the Java Community Process. This article explains RTSJ's features and the thinking behind the specification's design. The goal of the RTJEG, of which the authors are both members, was to provide a platform-a Java execution environment and application program interface (API)-that lets programmers correctly reason about the temporal behavior of executing software.

Extensibility safety and performance in the SPIN operating system

Abstract: This paper describes the motivation, architecture and performance of SPIN, an extensible operating system. SPIN provides an extension infrastructure, together with a core set of extensible services, that allow applications to safely change the operating system's interface and implementation. Extensions allow an application to specialize the underlying operating system in order to achieve a particular level of performance and functionality. SPIN uses language and link-time mechanisms to inexpensively export fine-grained interfaces to operating system services. Extensions are written in a type safe language, and are dynamically linked into the operating system kernel. This approach offers extensions rapid access to system services, while protecting the operating system code executing within the kernel address space. SPIN and its extensions are written in Modula-3 and run on DEC Alpha workstations.

Introduction to Embedded Systems - A Cyber-Physical Systems Approach

Abstract: The most visible use of computers and software is processing information for human consumption. The vast majority of computers in use, however, are much less visible. They run the engine, brakes, seatbelts, airbag, and audio system in your car. They digitally encode your voice and construct a radio signal to send it from your cell phone to a base station. They command robots on a factory floor, power generation in a power plant, processes in a chemical plant, and traffic lights in a city. These less visible computers are called embedded systems, and the software they run is called embedded software. The principal challenges in designing and analyzing embedded systems stem from their interaction with physical processes. This book takes a cyber-physical approach to embedded systems, introducing the engineering concepts underlying embedded systems as a technology and as a subject of study. The focus is on modeling, design, and analysis of cyber-physical systems, which integrate computation, networking, and physical processes. The second edition offers two new chapters, several new exercises, and other improvements. The book can be used as a textbook at the advanced undergraduate or introductory graduate level and as a professional reference for practicing engineers and computer scientists. Readers should have some familiarity with machine structures, computer programming, basic discrete mathematics and algorithms, and signals and systems.

Misconceptions about real-time computing: a serious problem for next-generation systems

Abstract: The author defines real-time computing and states and dispels the most common misconceptions about it. He discusses the fundamental technical issues of real-time computing. He examines specification and verification, scheduling theory, operating systems, programming languages and design methodology, distributed databases, artificial intelligence, fault tolerance, architectures, and communication. >