Xingang Guo

Bio: Xingang Guo is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: CPU modes & Central processing unit. The author has an hindex of 2, co-authored 3 publications receiving 430 citations.

A hierarchial CPU scheduler for multimedia operating systems

Abstract: The need for supporting variety of hard and soft real-time as well as best effort applications in a multimedia computing environment requires an operating system framework that: (1) enables different schedulers to be employed for different application classes, and (2) provides protection between the various classes of applications. We argue that these objectives can be achieved by hierarchical partitioning of CPU bandwidth, in which an operating system partitions the CPU bandwidth among various application classes, and each application class, in turn, partitions its allocation (potentially using a different scheduling algorithm) among its sub-classes or applications. We present Start-time Fair Queuing (SFQ) algorithm, which enables such hierarchical partitioning. We have implemented a hierarchical scheduler in Solaris 2.4. We describe our implementation, and demonstrate its suitability for multimedia operating systems.

Predictable cpu bandwidth management framework for next-generation operating systems

Abstract: Advances in hardware and software technologies have given software applications the ability to process multimedia data and to perform large-scale computation The increased ability has been one of the driving forces which have led to the proliferation of applications with heterogeneous performance requirements on various computer systems To satisfy these performance requirements, applications expect predictable resource allocation and different classes of applications require different resource management policies Conventional general purpose operating systems have been developed for a single class of best-effort applications, hence, are inadequate to support multiple classes of applications In this dissertation, we present the design, implementation and evaluation of a CPU bandwidth management framework that provides service differentiation and predictability in allocating CPU bandwidth, therefore, is suitable for next-generation operating systems In this dissertation, we decompose the task of managing CPU bandwidth to meet application performance requirements into sub-tasks and present our solution to each sub-task at the following three layers of abstraction: (1) Thread scheduling layer, we design a hierarchical thread scheduling structure which allows different thread scheduling policies to co-exist in the system and provides protection among them (2) Application management layer, we design mechanisms which allow application to be designated as the CPU band-width principal and ensure that the computation of an application, no matter carried out by which thread, consumes the bandwidth allocated to the application (3) QoS management layer, we design a bandwidth reservation interface that allows applications to utilize the various bandwidth allocation policies implemented by the previous two layers Hence, it facilitates the deployment and development of adaptable applications and supports the implementation of system-wide bandwidth usage policies We demonstrate that addressing the issues at any single layer has its limitations, a comprehensive CPU bandwidth management framework demands the integration of solutions to all the sub-tasks We implement such a 3-layer architecture in the kernel of Solaris 25 and demonstrate through experiments that such a CPU bandwidth management framework is able to provide service differentiation and predictability, hence, is able to meet heterogeneous application performance requirements

Resource containers: a new facility for resource management in server systems

Abstract: General-purpose operating systems provide inadequate support for resource management in large-scale servers. Applications lack sufficient control over scheduling and management of machine resources, which makes it difficult to enforce priority policies, and to provide robust and controlled service. There is a fundamental mismatch between the original design assumptions underlying the resource management mechanisms of current general-purpose operating systems, and the behavior of modern server applications. In particular, the operating system's notions of protection domain and resource principal coincide in the process abstraction. This coincidence prevents a process that manages large numbers of network connections, for example, from properly allocating system resources among those connections. We propose and evaluate a new operating system abstraction called a resource container, which separates the notion of a protection domain from that of a resource principal. Resource containers enable fine-grained resource management in server systems and allow the development of robust servers, with simple and firm control over priority policies.

Integrating multimedia applications in hard real-time systems

Abstract: This paper focuses on the problem of providing efficient run-time support to multimedia applications in a real-time system, where two types of tasks can coexist simultaneously: multimedia soft real-time tasks and hard real-time tasks. Hard tasks are guaranteed based on worst case execution times and minimum interarrival times, whereas multimedia and soft tasks are served based on mean parameters. The paper describes a server-based mechanism for scheduling soft and multimedia tasks without jeopardizing the a priori guarantee of hard real-time activities. The performance of the proposed method is compared with that of similar service mechanisms through extensive simulation experiments and several multimedia applications have been implemented on the HARTIK kernel.

Performance guarantees for Web server end-systems: a control-theoretical approach

Abstract: The Internet is undergoing substantial changes from a communication and browsing infrastructure to a medium for conducting business and marketing a myriad of services. The World Wide Web provides a uniform and widely-accepted application interface used by these services to reach multitudes of clients. These changes place the Web server at the center of a gradually emerging e-service infrastructure with increasing requirements for service quality and reliability guarantees in an unpredictable and highly-dynamic environment. This paper describes performance control of a Web server using classical feedback control theory. We use feedback control theory to achieve overload protection, performance guarantees, and service differentiation in the presence of load unpredictability. We show that feedback control theory offers a promising analytic foundation for providing service differentiation and performance guarantees. We demonstrate how a general Web server may be modeled for purposes of performance control, present the equivalents of sensors and actuators, formulate a simple feedback loop, describe how it can leverage on real-time scheduling and feedback-control theories to achieve per-class response-time and throughput guarantees, and evaluate the efficacy of the scheme on an experimental testbed using the most popular Web server, Apache. Experimental results indicate that control-theoretic techniques offer a sound way of achieving desired performance in performance-critical Internet applications. Our QoS (Quality-of-Service) management solutions can be implemented either in middleware that is transparent to the server, or as a library called by server code.

Start-time fair queueing: a scheduling algorithm for integrated services packet switching networks

Abstract: We present Start-time Fair Queuing (SFQ) algorithm that is computationally efficient, achieves fairness regardless of variation in a server capacity, and has the smallest fairness measure among all known fair scheduling algorithms. We analyze its throughput, single server delay, and end-to-end delay guarantee for variable rate Fluctuation Constrained (FC) and Exponentially Bounded Fluctuation (EBF) servers. We show that SFQ is better suited than Weighted Fair Queuing for integrated services networks and it is strictly better than Self Clocked Fair Queuing. To support heterogeneous services and multiple protocol families in integrated services networks, we present a hierarchical SFQ scheduler and derive its performance bounds. Our analysis demonstrates that SFQ is suitable for integrated services networks since it: (1) achieves low average as well as maximum delay for low-throughput applications (e.g., interactive audio, telnet, etc.); (2) provides fairness which is desirable for VBR video; (3) provides fairness, regardless of variation in a server capacity, for throughput-intensive, flow-controlled data applications; (4) enables hierarchical link sharing which is desirable for managing heterogeneity; and (5) is computationally efficient.

Start-time fair queueing: a scheduling algorithm for integrated services packet switching networks

Abstract: We present a start-time fair queueing (SFQ) algorithm that is computationally efficient and achieves fairness regardless of variation in a server capacity. We analyze its single server and end-to-end deadline guarantee for variable rate fluctuation constrained (FC) and exponentially bounded fluctuation (EBF) servers. To support heterogeneous services and multiple protocol families in integrated services networks, we present a hierarchical SFQ scheduler and derive its performance bounds. Our analysis demonstrates that SFQ is suitable for integrated services networks since it: (1) achieves low average as well as maximum delay for low-throughput applications (e.g., interactive audio, telnet, etc.); (2) provides fairness which is desirable for VBR video; (3) provides fairness, regardless of variation in server capacity, for throughput-intensive, flow-controlled data applications; (4) enables hierarchical link sharing which is desirable for managing heterogeneity; and (5) is computationally efficient.