Physical Sciences and Mathematics Commons^™

Flow And Congestion Control For Internet Streaming Applications, Shanwei Cen, Calton Pu, Jonathan Walpole

Computer Science Faculty Publications and Presentations

The emergence of streaming multimedia players provides users with low latency audio and video content over the Internet. Providing high-quality, best-effort, real-time multimedia content requires adaptive delivery schemes that fairly share the available network bandwidth with reliable data protocols such as TCP. This paper proposes a new flow and congestion control scheme, SCP (Streaming Control Protocol) , for real-time streaming of continuous multimedia data across the Internet. The design of SCP arose from several years of experience in building and using adaptive real-time streaming video players. SCP addresses two issues associated with real-time streaming. First, it uses a congestion control …

Dynamic Load Distribution In Mist, K. Al-Saqabi, R. M. Prouty, Dylan Mcnamee, Steve Otto, Jonathan Walpole

Computer Science Faculty Publications and Presentations

This paper presents an algorithm for scheduling parallel applications in large-scale, multiuser, heterogeneous distributed systems. The approach is primarily targeted at systems that harvest idle cycles in general-purpose workstation networks, but is also applicable to clustered computer systems and massively parallel processors. The algorithm handles unequal processor capacities, multiple architecture types and dynamic variations in the number of processes and available processors. Scheduling decisions are driven by the desire to minimize turnaround time while maintaining fairness among competing applications. For efficiency, the virtual processors (VPs) of each application are gang scheduled on some subset of the available physical processors.

A Toolkit For Specializing Production Operating System Code, Crispin Cowan, Dylan Mcnamee, Andrew P. Black, Calton Pu, Jonathan Walpole, Charles Krasic, Perry Wagle, Qian Zhang

Computer Science Faculty Publications and Presentations

Specialization has been recognized as a powerful technique for optimizing operating systems. However, specialization has not been broadly applied beyond the research community because the current techniques, based on manual specialization, are time-consuming and error-prone. This paper describes a specialization toolkit that should help broaden the applicability of specializing operating systems by assisting in the automatic generation of specialized code, and {\em guarding} the specialized code to ensure the specialized system continues to be correct. We demonstrate the effectiveness of the toolkit by describing experiences we have had applying it in real, production environments. We report on our experiences with …

Predictable File Access Latency For Multimedia, Dan Revel, Crispin Cowan, Dylan Mcnamee, Calton Pu, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Multimedia applications are sensitive to I/O latency and jitter when accessing data in secondary storage. Transparent adaptive prefetching (TAP) uses software feedback to provide multimedia applications with file system quality of service (QoS) guarantees. We are investigating how QoS requirements can be communicated and how they can be met by adaptive resource management. A preliminary test of adaptive prefetching is presented.

Physical Media Independence: System Support For Dynamically Available Network Interfaces, Jon Inouye, Jim Binkley, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Advances in hardware technology has fueled the proliferation of dynamically configurable network interface cards. This empowers mobile laptop users to select the most appropriate interface for their current environment. Unfortunately, the majority of system software remains "customized" for a particular network configuration, and assumes many network characteristics remain invariant over the runtime of the software. Physical Media Independence (PMI) is the concept of making assumptions about a particular device explicit, detecting events which invalidate these assumptions, and recovering once events are detected. This paper presents a model supporting PMI. Based on device availablilty, the model identifies implicit device-related assumptions made …

A Specialization Toolkit To Increase The Diversity Of Operating Systems, Calton Pu, Andrew P. Black, Crispin Cowan, Jonathan Walpole, Charles Consel

Computer Science Faculty Publications and Presentations

Virus and worm attacks that exploit system implementation details can be countered with a diversified set of implementations. Furthermore, immune systems show that attacks from previously unknown organisms require effective dynamic response. In the Synthetix project, we have been developing a specialization toolkit to improve the performance of operating system kernels. The toolkit helps programmers generate and manage diverse specialized implementations of software modules. The Tempo-C specializer tool generates different versions for both compile-time and run-time specialization. We are now adapting the toolkit to improve operating system survivability against implementations attacks.

Multimedia Applications Require Adaptive Cpu Scheduling, Veronica Baiceanu, Crispin Cowan, Dylan Mcnamee, Calton Pu, Jonathan Walpole

Computer Science Faculty Publications and Presentations

CPU scheduling and admission testing for multimedia applications have been extensively studied, and various solutions have been proposed using assorted simplifying assumptions. However, we believe that the complexity and dynamic behavior of multimedia applications and systems make static solutions hard to apply in real-world situations. We are analyzing the difficulties that arise when applying the rate-monotonic (RM) scheduling algorithm and the corresponding admission tests for CPU management, in the context of real multimedia applications running on real systems. RM requires statically predictable, periodic workloads, and while multimedia applications appear to be periodic, in practice they exhibit numerous variabilities in workload. …

Adaptive Methods For Distributed Video Presentation, Crispin Cowan, Shanwei Cen, Jonathan Walpole, Carlton Pu

Computer Science Faculty Publications and Presentations

This paper describes problems and solutions for delivering real-time, multi-media presentations across the Internet. A key characteristic of presentations of continuous media datatypes, such as digital video and audio, is their need for predictable real-time data delivery. For example, an NTSC quality video presentation requires video frames to be displayed every 1/30th of a second. Variations in this display rate can be observable as stalls or glitches in the video stream and reduce the quality of the presentation [6]. Delivering such presentations across the Internet is difficult because highly variable band- width and latency make it difficult to predict the …

Device And Physical Data Independence For Multimedia Presentations, Richard Staehli, Jonathan Walpole, David Maier

Computer Science Faculty Publications and Presentations

Multimedia computing promises access to any type of visual or aural medium on the desktop. But in this networked future, will every type of media be accessible from every terminal device? Current multimedia standards do not allow content that is authored for high-bandwidth workstations to scale down for low-bandwidth applications. The problem is that application requests are commonly interpreted as requests for the highest possible quality and resource overloads are handled by ad hoc methods. We can begin to solve this problem by specifying Quality of Service (QOS) requirements based on functionality rather than on content encoding and device capabilities.

Customizable Operating Systems, Jonathan Walpole, Crispin Cowan, Andrew P. Black, Jon Inouye, Calton Pu, Shanwei Cen

Computer Science Faculty Publications and Presentations

A customizable operating system is one that can adapt to improve its functionality or performance. The need for customizable and application-specific operating systems has been recognized for many years, but they have yet to appear in the commercial market. This paper explores the notion of operating system customizability and examines the limits of existing approaches. The paper begins by surveying system structuring approaches for the safe and efficient execution of customizable operating systems. Then it discusses the burden that existing approaches impose on application software, and explores techniques for reducing this burden. Finally, support for customizability in the Synthetix project …

Quality Of Service Specification For Multimedia Presentations, Richard Staehli, Jonathan Walpole, David Maier

Computer Science Faculty Publications and Presentations

The bandwidth limitations of multimedia systems force tradeoffs between presentation data fidelity and real-time performance. For example, digital video is commonly encoded with lossy compression to reduce bandwidth and frames may be skipped during playback to maintain synchronization. These tradeoffs depend on device performance and physical data representations that are hidden by a database system. If a multimedia database is to support digital video and other continuous media data types, we argue that the database should provide a Quality of Service (QOS) interface to allow application control of presentation timing and information loss tradeoffs.

This paper proposes a data model …

Device And Physical Data Independence For Multimedia Presentations, Richard Staehli, Jonathan Walpole, David Maier

Computer Science Faculty Publications and Presentations

Multimedia computing promises access to any type of visual or aural medium on the desktop. But in this networked future, will every type of media be accessible from every terminal device? Current multimedia standards do not allow content that is authored for high-bandwidth workstations to scale down for low-bandwidth applications. The problem is that application requests are commonly interpreted as requests for the highest possible quality and resource overloads are handled by ad hoc methods. We can begin to solve this problem by specifying Quality of Service (QOS) requirements based on functionality rather than on content encoding and device capabilities.

Mpvm: A Migration Transparent Version Of Pvm, Jeremy Casas, Dan Clark, Ravi Konuru, Steve Otto, Robert Prouty, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Parallel Virtual Machine (PVM) is a widely-used software system that allows a heterogeneous set of parallel and serial UNIX-based computers to be programmed as a single message-passing parallel machine, In this paper, an extension to PVM to support dynamic process migration is presented. Support for migration is important in general-purpose workstation environments since it allows parallel computations to co-exist with other applications, using idle-cycles as they become available and off-loading from workstations when they are no longer free. A description and evaluation of the design and implementation of the prototype Migratable PVM system is presented together with some performance results.

Scheduling Of Parallel Jobs On Dynamic, Heterogenous Networks, Dan Clark, Jeremy Casas, Steve Otto, Robert Prouty, Jonathan Walpole

Computer Science Faculty Publications and Presentations

In using a shared network of workstations for parallel processing, it is not only important to consider heterogeneity and differences in processing power between the workstations but also the dynamics of the system as a whole. In such a computing environment where the use of resources vary as other applications consume and release resources, intelligent scheduling of the parallel jobs onto the available resources is essential to maximize resource utilization. Despite this realization, however, there are few systems available that provide an infrastructure for the easy development and testing of these intelligent schedulers. In this paper, an infrastructure is presented …

Optimizing Object Invocation Using Optimistic Incremental Specialization, Jon Inouye, Andrew P. Black, Charles Consel, Calton Pu, Jonathan Walpole

Computer Science Faculty Publications and Presentations

To make object invocation efficient, it is important to minimize overhead. In general, overhead is incurred in order to maintain transparency; with the advent of mobile computer systems, persistence, increasing security and privacy concerns, transparency becomes more expensive and overhead is increasing. Invocation mechanisms maintain transparency by finding objects, choosing communication media, performing data translation into common formats (e.g., XDR), marshalling arguments, encrypting confidential data, etc. Performing all of these operations on every invocation would lead to unacceptable performance, so designers often avoid operations by specializing object invocation for more restricted environments. For example, the Emerald compiler performs several optimizations …

Objects To The Rescue! Or Httpd: The Next Generation Operating System, Andrew P. Black, Jonathan Walpole

Computer Science Faculty Publications and Presentations

This position paper suggests that object-oriented operating systems may provide the means to meet the ever-growing demands of applications. As an example of a successful OOOS, we cite the http daemon. To support the contention that httpd is in fact an operating system, we observe that it implements uniform naming, persistent objects and an invocation meta-protocol, specifies and implements some useful objects, and provides a framework for extensibility.We also believe that the modularity that is characteristic of OO systems should provide a performance benefit rather than a penalty. Our ongoing work in the Synthetix project at OGI is exploring the …

A User-Level Process Package For Concurrent Computing, Ravi Konuru, Steve Otto, Jonathan Walpole, Robert Prouty, Jeremy Casas

Computer Science Faculty Publications and Presentations

A lightweight user-level process(ULP) package for parallel computing is described. Each ULP has its own register context, stack, data and heap space and communication with other ULPs is performed using locally synchronous, location transparent, message passing primitives. The aim of the package is to provide support for lightweight over-decomposition, optimized local communication and transparent dynamic migration. The package supports a subset of the Parallel Virtual Machine(PVM) interface[Sun90).

Script-Based Qos Specifications For Multimedia Presentations, Richard Staehli, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Multimedia presentations can convey information not only by the sequence of events but by their timing. The correctness of such presentations thus depends on the timing of events as well as their sequence and content. This paper introduces a formal specification language for playback of real-time presentations. The main contribution of this language is a quality of service (QOS) specification that relaxes resolution and synchronization requirements for playback. Our definitions give a precise meaning to the correctness of a presentation. This specification language will form the basis for a QOS interface for reservation of operating system resources.

A Study Of Dynamic Optimization Techniques: Lessons And Directions In Kernel Design, Calton Pu, Jonathan Walpole

Computer Science Faculty Publications and Presentations

The Synthesis kernel [21,22,23,27,28] showed that dynamic code generation, software feedback, and fine-grain modular kernel organization are useful implementation techniques for improving the performance of operating system kernels. In addition, and perhaps more importantly, we discovered that there are strong interactions between the techniques. Hence, a careful and systematic combination of the techniques can be very powerful even though each one by itself may have serious limitations. By identifying these interactions we illustrate the problems of applying each technique in isolation to existing kernels. We also highlight the important common under-pinnings of the Synthesis experience and present our ideas on …

Porting Chorus To The Pa-Risc: Building, Debugging, Testing And Validation, Ravi Konuru, Marion Hakanson, Jon Inouye, Jonathan Walpole

Computer Science Faculty Publications and Presentations

This document is part of a series of reports describing the design decisions made in porting the Chorus Operating System to the Hewlett-Packard 9000 Series 800 workstation. This document describes the environment for building the Chorus kernel, the various kernel tests, and the debugging environment used for porting the Chorus operating system to the HP PA-RISC.

The information contained in this paper will be of interest to people who wish to:

• Use the PA-Chorus kernel for development and/or modification, • Know about the build environment for Chorus kernel on PA-RISC, • Know about the PA-Chorus approach to debugging, • …

Porting Chorus To The Pa-Risc: Project Overview, Jonathan Walpole, Marion Hakanson, Jon Inouye, Ravi Konuru

Computer Science Faculty Publications and Presentations

This document is part of a series of reports describing the design decisions made in porting the Chorus Operating System to the Hewlett-Packard 9000 Series 800 workstation. This document presents an overview of the project, and outlines the other reports in the series and the relationships between them.

Porting Chorus To The Pa-Risc: Overall Evaluation, Jonathan Walpole, Marion Hakanson, Jon Inouye, Ravi Konuru

Computer Science Faculty Publications and Presentations

This document is part of a series of reports describing the design decisions made in porting the Chorus Operating System kernel to the Hewlett-Packard 9000 Series 800 workstation. This document summarizes the matches and mis-matches between Chorus and the PA-RISC and outlines the general lessons learned during the project.

This document is intended for people who are interested in (a) the separation of machinedependent micro-kernel code from machine-independent micro-kernel code, (b) the interaction between operating system design and the PA-RISC architecture, and (c) the portability ofthe Chorus operating system.

The first report in the series, Porting Chorus to the PA-RISe: …

Porting Chorus To The Pa-Risc: Virtual Memory Manager, Jon Inouye, Marion Hakanson, Ravi Konuru, Jonathan Walpole

Computer Science Faculty Publications and Presentations

This document describes the port ofthe Chorus virtual memory manager to the Hewlett-Packard Precision Architecture rusc (PA-RISC) workstation. The information contained in this paper will be of interest to people who:

• intend to port the Chorus virtual memory section. • intend to port a virtual memory design to the Hewlett-Packard PA-RISC.

The reader is strongly encouraged to read the following PA-Chorus documents before reading this document:

• Technical Report CSE-92-3, Porting Chorus to the PA-RISC: Project Overview

Porting Chorus To The Pa-Risc: Booting, Jon Inouye, Ravi Konuru, Jonathan Walpole, Marion Hakanson

Computer Science Faculty Publications and Presentations

We started out with the low level Tut (HP-CX 2.0) boot code. One of our goals was to reuse as much of this code as possible, which would reduce the amount of low level code we would have to debug. This was very important, especially fiince the RP 9000/834 has a very complex I/O architecture and we lacked any sophisticated debugging tools. Writing the PA-Chorus boot code involved modifying the Tut code to match the Chorus startup sequence. In the remainder of this section, we present an overview of the PA-RISC boot mechanisms and the Chorus startup sequence. Sectlon 2 …

Porting The Chorus Supervisor And Related Low-Level Functions To The Pa-Risc, Ravi Konuru, Marion Hakanson, Jon Inouye, Jonathan Walpole

Computer Science Faculty Publications and Presentations

This document is part of a series of reports describing the design decisions made in porting the Chorus Operating System to the Hewlett-Packard 9000 Series 800 workstation.

The Supervisor is the name given by Chorus to a collection of low-level functions that are machine dependent and have to be implemented when Chorus is ported from one machine to another. The Supervisor is responsible for interrupt, trap and exception handling, managing low-level thread initialization, context switch, kernel initialization, managing simple devices (timer and console) and offering a low-level debugger. This document describes the port of the Supervisor and related low-level functions. …

Moment-Curvature-Thrust Relationships In Hybrid Members, Douglas Wrenn Fiala

Dissertations and Theses

In order to overcome the difficulties encountered in closed form solutions, moment-curvature-thrust relationships are developed for hybrid and nonhybrid cross sections utilizing an open form method. The use of horizontal sectors permits the inclusion of residual stresses and/or nonbilinear stress-strain relationships, if desired. Theoretical and experimental data are compared. Applications to circular tubes and other cross sections are discussed. Results indicate that open form solutions are feasible for calculating moment-curvature-thrust data. Hybrid cross sections are easily treated by open form solutions.