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Articles 31 - 60 of 63
Full-Text Articles in Computer Engineering
What Is Rcu, Fundamentally?, Paul E. Mckenney, Jonathan Walpole
What Is Rcu, Fundamentally?, Paul E. Mckenney, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Read-copy update (RCU) is a synchronization mechanism that was added to the Linux kernel in October of 2002. RCU achieves scalability improvements by allowing reads to occur concurrently with updates. In contrast with conventional locking primitives that ensure mutual exclusion among concurrent threads regardless of whether they be readers or updaters, or with reader-writer locks that allow concurrent reads but not in the presence of updates, RCU supports concurrency between a single updater and multiple readers. RCU ensures that reads are coherent by maintaining multiple versions of objects and ensuring that they are not freed up until all pre-existing read-side …
Directflow: A Domain-Specific Language For Information-Flow Systems, Andrew P. Black, Chuan-Kai Lin
Directflow: A Domain-Specific Language For Information-Flow Systems, Andrew P. Black, Chuan-Kai Lin
Computer Science Faculty Publications and Presentations
Programs that process streams of information are commonly built by assembling reusable information-flow components. In some systems the components must be chosen from a pre-defined set of primitives; in others the programmer can create new custom components using a general-purpose programming language. Neither approach is ideal: restricting programmers to a set of primitive components limits the expressivity of the system, while allowing programmers to define new components in a general-purpose language makes it difficult or impossible to reason about the composite system. We advocate defining information-flow components in a domain-specific language (DSL) that enables us to infer the properties of …
The Case For Thoroughly Testing Complex System Dynamic Models, Wayne Wakeland, Megan Hoarfrost
The Case For Thoroughly Testing Complex System Dynamic Models, Wayne Wakeland, Megan Hoarfrost
Systems Science Faculty Publications and Presentations
In order to determine whether model testing is as useful as suggested by modeling experts, the full battery of model tests recommended by Forrester, Senge, Sterman, and others was applied retrospectively to a complex previously-published system dynamics model. The time required to carry out each type of test was captured, and the benefits that resulted from applying each test was determined subjectively. The resulting benefit to cost ratios are reported. These ratios suggest that rather than focusing primarily on sensitivity testing, modelers should consider other types of model tests such as extreme condition tests and family member tests. The study …
Using Dynamic Optimization For Control Of Real Rate Cpu Resource Management Applications, Varin Vahia, Ashvin Goel, David Steere, Jonathan Walpole, Molly H. Shor
Using Dynamic Optimization For Control Of Real Rate Cpu Resource Management Applications, Varin Vahia, Ashvin Goel, David Steere, Jonathan Walpole, Molly H. Shor
Computer Science Faculty Publications and Presentations
In this paper we design a proportional-period optimal controller for allocating CPU to real rate multimedia applications on a general-purpose computer system. We model this computer system problem in to state space form. We design a controller based on dynamic optimization LQR tracking techniques to minimize short term and long term time deviation from the current time stamp and also CPU usage. Preliminary results on an experimental set up are encouraging.
Adaptive Live Video Streaming By Priority Drop, Jie Huang, Charles Krasic, Jonathan Walpole
Adaptive Live Video Streaming By Priority Drop, Jie Huang, Charles Krasic, Jonathan Walpole
Computer Science Faculty Publications and Presentations
In this paper we explore the use of Priority-progress streaming (PPS) for video surveillance applications. PPS is an adaptive streaming technique for the delivery of continuous media over variable bit-rate channels. It is based on the simple idea of reordering media components within a time window into priority order before transmission. The main concern when using PPS for live video streaming is the time delay introduced by reordering. In this paper we describe how PPS can be extended to support live streaming and show that the delay inherent in the approach can be tuned to satisfy a wide range of …
A Lessons Learned Repository For Computer Forensics, Warren Harrison, George Heuston, Mark Morrissey, David Aucsmith, Sarah Mocas, Steve Russelle
A Lessons Learned Repository For Computer Forensics, Warren Harrison, George Heuston, Mark Morrissey, David Aucsmith, Sarah Mocas, Steve Russelle
Computer Science Faculty Publications and Presentations
The Law Enforcement community possesses a large, but informal, community memory with respect to digital forensics. Large, because the experiences of every forensics technician and investigator contribute to the whole. Informal because there is seldom an explicit mechanism for disseminating this wisdom except “over the water cooler”. As a consequence, the same problems and mistakes continue to resurface and the same solutions are re-invented. In order to better exploit this informal collection of wisdom, the key points of each experience can be placed into a Repository for later dissemination. We describe a web-based Lessons Learned Repository (LLR) that facilitates contribution …
Thread Transparency In Information Flow Middleware, Rainer Koster, Andrew P. Black, Jie Huang, Jonathan Walpole, Calton Pu
Thread Transparency In Information Flow Middleware, Rainer Koster, Andrew P. Black, Jie Huang, Jonathan Walpole, Calton Pu
Computer Science Faculty Publications and Presentations
Existing middleware is based on control-flow centric interaction models such as remote method invocations, poorly matching the structure of applications that process continuous information flows. Difficulties cultiesin building this kind of application on conventional platforms include flow-specific concurrency and timing requirements, necessitating explicit management of threads, synchronization, and timing by the application programmer. We propose Infopipes as a high-level abstraction for information flows, and we are developing a middleware framework that supports this abstraction. Infopipes transparently handle complexities associated with control flow and multi-threading. From high-level configuration descriptions the platform determines what parts of a pipeline require separate threads or …
Reifying Communication At The Application Level, Andrew P. Black, Jie Huang, Jonathan Walpole
Reifying Communication At The Application Level, Andrew P. Black, Jie Huang, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Middleware, from the earliest RPC systems to recent Object-Oriented Remote Message Sending (RMS) systems such as Java RMI and CORBA, claims transparency as one of its main attributes. Coulouris et al. define transparency as “the concealment from the … application programmer of the separation of components in a distributed system.” They go on to identify eight different kinds of transparency.
We considered titling this paper “Transparency Considered Harmful”, but that title is misleading because it implies that all kinds of transparency are bad. This is not our view. Rather, we believe that the choice of which transparencies should be offered …
Rate-Matching Packet Scheduler For Real-Rate Applications, Kang Li, Jonathan Walpole, Dylan Mcnamee, Calton Pu, David Steere
Rate-Matching Packet Scheduler For Real-Rate Applications, Kang Li, Jonathan Walpole, Dylan Mcnamee, Calton Pu, David Steere
Computer Science Faculty Publications and Presentations
A packet scheduler is an operating system component that controls the allocation of network interface bandwidth to outgoing network flows. By deciding which packet to send next, packet schedulers not only determine how bandwidth is shared among flows, but also play a key role in determining the rate and timing behavior of individual flows. The recent explosion of rate and timing-sensitive flows, particularly in the context of multimedia applications, has focused new interest on packet schedulers. Next generation packet schedulers must not only ensure separation among flows and meet real-time performance constraints, they must also support dynamic fine-grain reallocation of …
Application Of Control Theory To Modeling And Analysis Of Computer Systems, Molly H. Shor, Kang Li, Jonathan Walpole, David Steere, Calton Pu
Application Of Control Theory To Modeling And Analysis Of Computer Systems, Molly H. Shor, Kang Li, Jonathan Walpole, David Steere, Calton Pu
Computer Science Faculty Publications and Presentations
Experimentally, we show that Transmission Control Protocol (TCP)’s congestion control algorithm results in dynamic behavior similar to a stable limit cycle (attractor) when data from TCP flow into a fixed-size buffer and data is removed from the buffer at a fixed service rate. This setup represents how TCP buffers packets for transmission onto the network, with the network represented by a fixed-size buffer with a fixed service rate. The closed trajectory may vary slightly from period to period due to the discrete nature of computer systems. The size of the closed trajectory is a function of the network’s buffer size …
Aspects Of Information Flow, Andrew P. Black, Jonathan Walpole
Aspects Of Information Flow, Andrew P. Black, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Along with our colleagues at the Oregon Graduate Institute and Georgia Institute of Technology, we have recently been experimenting with real-rate systems, that is, systems that are required to move data from one place to another at defined rates, such as 30 items per second. Audio conferencing or streaming video systems are typical: they are required to deliver video or audio frames from a source (a server or file system) in one place to a sink (a display or a sound generator) in another; the frames must arrive periodically, with constrained latency and jitter. We have successfully built such systems …
Work In Progress: Automating Proportion/Period Scheduling, David Steere, Jonathan Walpole, Calton Pu
Work In Progress: Automating Proportion/Period Scheduling, David Steere, Jonathan Walpole, Calton Pu
Computer Science Faculty Publications and Presentations
The recent effort to define middleware capable of supporting real-time applications creates the opportunity to raise the level of abstraction presented to the programmer. We propose that proportion/period is a better abstraction for specifying resource needs and allocation than priorities. We are currently investigating techniques to address some issues that are restricting use of proportion/period scheduling to research real-time prototypes. In particular, we are investigating techniques to automate the task of selecting proportion and period, and that allow proportion/period to incorporate job importance under overload conditions.
Fine-Grain Period Adaptation In Soft Real-Time Environments, David Steere, Joshua Gruenberg, Dylan Mcnamee, Calton Pu, Jonathan Walpole
Fine-Grain Period Adaptation In Soft Real-Time Environments, David Steere, Joshua Gruenberg, Dylan Mcnamee, Calton Pu, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Reservation-based scheduling delivers a proportion of the CPU to jobs over a period of time. In this paper we argue that automatically determining and assigning this period is both possible and useful in general purpose soft real-time environments such as personal computers and information appliances. The goal of period adaptation is to select the period over which a job is guaranteed to receive its portion of the CPU dynamically and automatically. The choice of period represents a trade-off between the amount of jitter observed by the job and the overall efficiency of the system. Secondary effects of period include quantization …
Qos Scalability For Streamed Media Delivery, Charles Krasic, Jonathan Walpole
Qos Scalability For Streamed Media Delivery, Charles Krasic, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Applications with real-rate progress requirements, such as mediastreaming systems, are difficult to deploy in shared heterogenous environments such as the Internet. On the Internet, mediastreaming systems must be capable of trading off resource requirements against the quality of the media streams they deliver, in order to match wide-ranging dynamic variations in bandwidth between servers and clients. Since quality requirements tend to be user- and task-specific, mechanisms for capturing quality of service requirements and mapping them to appropriate resource-level adaptation policies are required. In this paper, we describe a general approach for automatically mapping user-level quality of service specifications onto resource …
Adaptive Resource Management Via Modular Feedback Control, Ashvin Goel, David Steere, Calton Pu, Jonathan Walpole
Adaptive Resource Management Via Modular Feedback Control, Ashvin Goel, David Steere, Calton Pu, Jonathan Walpole
Computer Science Faculty Publications and Presentations
A key feature of tomorrow’s operating systems and runtime environments is their ability to adapt. Current state of the art uses an ad-hoc approach to building adaptive software, resulting in systems that can be complex, unpredictable and brittle. We advocate a modular and methodical approach for building adaptive system software based on feedback control. The use of feedback allows a system to automatically adapt to dynamically varying environments and loads, and allows the system designer to utilize the substantial body of knowledge in other engineering disciplines for building adaptive systems. We have developed a toolkit called SWiFT that embodies this …
Quality Of Service Semantics For Multimedia Database Systems, Jonathan Walpole, Charles Krasic, Ling Liu, David Maier, Calton Pu, Dylan Mcnamee, David Steere
Quality Of Service Semantics For Multimedia Database Systems, Jonathan Walpole, Charles Krasic, Ling Liu, David Maier, Calton Pu, Dylan Mcnamee, David Steere
Computer Science Faculty Publications and Presentations
Quality of service (QoS) support has been a hot research topic in multimedia databases, and multimedia systems in general, for the past several years. However, there remains little consensus on how QoS support should be provided. At the resource-management level, systems designers are still debating the suitability of reservation- based versus adaptive QoS management. The design of higher system layers is less clearly understood, and the specification of QoS requirements in domain-specific terms is still an open research topic. To address these issues, we propose a QoS model for multimedia databases. The model covers the specification of user-level QoS preferences …
Adaptation Space: Surviving Non-Maskable Failures, Crispin Cowan, Lois Delcambre, Anne-Francoise Le Meur, Ling Liu, David Maier, Dylan Mcnamee, Michael Miller, Calton Pu, Perry Wagle, Jonathan Walpole
Adaptation Space: Surviving Non-Maskable Failures, Crispin Cowan, Lois Delcambre, Anne-Francoise Le Meur, Ling Liu, David Maier, Dylan Mcnamee, Michael Miller, Calton Pu, Perry Wagle, Jonathan Walpole
Computer Science Faculty Publications and Presentations
Some failures cannot be masked by redundancies, because an unanticipated situation occurred, because fault-tolerance measures were not adequate, or because there was a security breach (which is not amenable to replication). Applications that wish to continue to offer some service despite nonmaskable failure must adapt to the loss of resources. When numerous combinations of non-maskable failure modes are considered, the set of possible adaptations becomes complex. This paper presents adaptation spaces, a formalism for navigating among combinations of adaptations. An adaptation space describes a collection of possible adaptations of a software component or system, and provides a uniform way of …
Stackguard: Automatic Adaptive Detection And Prevention Of Buffer-Overflow Attacks, Crispin Cowan, Calton Pu, David Maier, Heather Hinton, Jonathan Walpole, Peat Bakke, Steve Beattie, Aaron Grier, Perry Wagle, Qian Zhang
Stackguard: Automatic Adaptive Detection And Prevention Of Buffer-Overflow Attacks, Crispin Cowan, Calton Pu, David Maier, Heather Hinton, Jonathan Walpole, Peat Bakke, Steve Beattie, Aaron Grier, Perry Wagle, Qian Zhang
Computer Science Faculty Publications and Presentations
This paper presents a systematic solution to the persistent problem of buffer overflow attacks. Buffer overflow attacks gained notoriety in 1988 as part of the Morris Worm incident on the Internet. While it is fairly simple to fix individual buffer overflow vulnerabilities, buffer overflow attacks continue to this day. Hundreds of attacks have been discovered, and while most of the obvious vulnerabilities have now been patched, more sophisticated buffer overflow attacks continue to emerge.
We describe StackGuard: a simple compiler technique that virtually eliminates buffer overflow vulnerabilities with only modest performance penalties. Privileged programs that are recompiled with the StackGuard …
A Player For Adaptive Mpeg Video Streaming Over The Internet, Jonathan Walpole, Rainer Koster, Shanwei Cen, Crispin Cowan, David Maier, Dylan Mcnamee, Calton Pu, David Steere, Liujin Yu
A Player For Adaptive Mpeg Video Streaming Over The Internet, Jonathan Walpole, Rainer Koster, Shanwei Cen, Crispin Cowan, David Maier, Dylan Mcnamee, Calton Pu, David Steere, Liujin Yu
Computer Science Faculty Publications and Presentations
This paper describes the design and implementation of a real-time, streaming, Internet video and audio player. The player has a number of advanced features including dynamic adaptation to changes in available bandwidth, latency and latency variation; a multi-dimensional media scaling capability driven by user-specified quality of service (QoS) requirements; and support for complex content comprising multiple synchronized video and audio streams. The player was developed as part of the QUASAR t project at Oregon Graduate Institute, is freely available, and serves as a testbed for research in adaptive resource management and QoS control.
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
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 …
A Specialization Toolkit To Increase The Diversity Of Operating Systems, Calton Pu, Andrew P. Black, Crispin Cowan, Jonathan Walpole, Charles Consel
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.
Customizable Operating Systems, Jonathan Walpole, Crispin Cowan, Andrew P. Black, Jon Inouye, Calton Pu, Shanwei Cen
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 …
Device And Physical Data Independence For Multimedia Presentations, Richard Staehli, Jonathan Walpole, David Maier
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.
Scheduling Of Parallel Jobs On Dynamic, Heterogenous Networks, Dan Clark, Jeremy Casas, Steve Otto, Robert Prouty, Jonathan Walpole
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 …
A User-Level Process Package For Concurrent Computing, Ravi Konuru, Steve Otto, Jonathan Walpole, Robert Prouty, Jeremy Casas
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
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
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
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
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: Booting, Jon Inouye, Ravi Konuru, Jonathan Walpole, Marion Hakanson
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 …