Constant bandwidth supply for priority processing

For providing distributed multimedia applications with end-to-end QoS (Quality of Service) guarantees, resource reservation based control mechanisms should be employed in both of networks and end systems. In this paper, we implement and evaluate a resource allocation scheme to allocate both of network and server CPU resources to clients in an integrated manner. For this purpose, we use HiTactix for real-time OS and TTCP/ITM for the resource reservation network. Through experimentations using our implemented video transfer system, we confirm that our proposed scheme can achieve an effective use of resources while providing high quality video transfer.

Real-Time Imaging, 2003

The transmission of video requires new service models for providing Quality of Service (QoS). Some of these models are based on resource reservation and admission control while others rely on resource provisioning. In both approaches, optimally estimating the resource requirements of a given video is a key issue, since they are always very demanding. This paper introduces a fast and bounded method to optimise the required network resources (bandwidth) to guarantee a maximum deterministic delay for a given workload and network state. The method is based on characterising the workload of a stored video using a reduced set of points obtained from an off-line analysis of its empirical envelope. The paper also proposes the above workload characterisation to perform the admission control test using a WFQ scheduler. The evaluation of this scheme shows that it can achieve an utilisation higher than a 50% for a single flow with a one-second deadline and reach up to an 80% with a 5second delay. Results are also compared to tests based on EDF schemes, which have been proved to be optimal with one node. It is shown that the proposed scheme is a little less efficient than the optimal EDF scheduler with one node (as expected), but it is practically as efficient (or even better with a moderately high number of nodes) than the best known RC-EDF policies with several nodes. This is an interesting result because it shows that the WFQ schedulers can achieve a similar efficiency to EDF schedulers avoiding the complexity of their admission control tests.

2010 22nd Euromicro Conference on Real-Time Systems, 2010

Modern real-time systems increasingly operate with multiple interactive applications. While these systems often require reliable quality of service (QoS) for the applications, even under heavy workloads, many existing CPU schedulers are not very capable of satisfying such requirements. In this paper, we design and implement an Advanced Interactive and Realtime Scheduler, called AIRS. AIRS is aimed at supporting systems that run multiple interactive real-time applications, particularly on multicore platforms. It provides a new CPU reservation mechanism to enhance the QoS of the overall system. The reservation algorithm is based on the prior Constant Bandwidth Server (CBS) algorithm, but is more flexible and efficient, when multiple applications reserve CPU bandwidth. It also provides a new multicore scheduler to improve the absolute CPU bandwidth available for the applications to perform well. The scheduling algorithm is subject to the prior Earliest Deadline First with Window-constraint Migration (EDF-WM) algorithm, but is extended to work with the new CPU reservation mechanism. Experimental evaluation shows that AIRS delivers higher quality to simultaneous playback of multiple movies than the existing real-time scheduler. It also demonstrates that AIRS offers hard timing guarantees for randomly-generated task sets with heavy workloads.

IEEE Transactions on Parallel and Distributed Systems, 2003

Network Of Workstations (NOW) platforms put together with off-the-shelf workstations and networking hardware have become a cost effective, scalable, and flexible platform for video processing applications. Still, one has to manually schedule an algorithm to the available processors of the NOW to make efficient use of the resources. However, this approach is time-consuming and impractical for a video processing system that must perform a variety of different algorithms, with new algorithms being constantly developed. Improved support for program development is absolutely necessary before the full benefits of parallel architectures can be realized for video processing applications. Toward this goal, an automatic compile-time scheduler has been developed to schedule input tasks of video processing applications with precedence constraints onto available processors. The scheduler exploits both spatial (parallelism) and temporal (pipelining) concurrency to make the best use of machine resources. Two important scheduling problems are addressed. First, given a task graph and a desired throughput, a schedule is constructed to achieve the desired throughput with the minimum number of processors. Second, given a task graph and a finite set of available resources, a schedule is constructed such that the throughput is maximized while meeting the resource constraints. Results from simulations show that the scheduler and proposed optimization techniques effectively tackle these problems by maximizing processor utilization. A code generator has been developed to generate parallel programs automatically. The tools developed in this paper make it much easier for a programmer to develop video processing applications on these parallel architectures.

ACM SIGBED Review, 2015

In this paper, we propose a new protocol for handling resource sharing among prioritized real-time applications composed on a multiprocessor platform. We propose an optimal priority assignment algorithm which assigns unique priorities to the applications based on information in their interfaces. We have performed experimental evaluations to compare the proposed protocol (called MSOS-Priority) to the current state of the art locking protocols under multiprocessor partitioned scheduling, i.e., MPCP, MSRP, FMLP, MSOS, and OMLP. The evaluations show that MSOS-Priority mostly performs significantly better than alternative approaches.

2011

The last decade a trend can be observed towards multi-processor Systems-on-Chip (MPSoC) platforms for satisfying the high computational requirements of modern multimedia applications. The research community has mainly focused on communication issues (e.g. bus vs. networks-on-chip). Real-time operating systems for MPSoCs however, have gotten very little attention. Existing techniques like rate-monotonic scheduling from the real-time community are rarely applicable, because contemporary high-performance media processors (like Cell, graphics processors) do not support preemption. Furthermore, rate-monotonic scheduling cannot deal with multiple (heterogeneous) processors, data dependencies, and dynamically varying execution times that characterize modern media applications. This paper proposes new techniques to manage the computational resources of MPSoCs at run-time. We compare a centralized resource manager (RM) to two versions (Credit based and Rate based) of a novel, more distributed RM. The distributed RMs are developed to cope with a larger number of processors as well as concurrently executing applications. Experiments show that our distributed resource managers are more scalable, deal better with application and user dynamics, and require less buffering, while effectively enforcing throughput constraints.

This paper describes the hardware and system software support for multi-tasking a dual-processor used in a multimedia system. One of the two processors is a conventional RISC processor, the other is a vector processor of new design. There is no commonality in the instruction sets of the two processors. We schedule the former preemptively and the latter cooperatively via check points, resulting in an asymmetric scheduling algorithm. Media processing requires predictable scheduling behaviors. Programmers can inform our scheduler of the Real Time requirements of their computations using time-constraints. Scheduling decisions are very fine-grained, and place strong efficiency demands on the system implementation.

IEEE Transactions on Circuits and Systems for Video Technology, 2016

To challenge real-time encoding of high-definition video sequences on heterogeneous desktop systems, a collaborative central processing units (CPU) + graphics processing unit (GPU) framework for interloop video encoding is proposed herein. The proposed framework considers the overall complexity of the collaborative interloop encoding as a unified optimization problem. Several functional blocks are integrated for simultaneous execution control, automatic data access management, performance characterization, and adaptive scheduling and load balancing. These blocks aim at fully exploiting the performance of heterogeneous devices, asymmetric bandwidth of communication links, and several levels of concurrency between computation and communication. To support a wide range of CPU and GPU architectures, a specific encoding library is developed with highly optimized algorithms for all interloop modules. The experimental results show that the proposed framework allows achieving a real-time encoding of full high-definition sequences in several CPU + GPU systems. It also delivers performance improvements of up to 61.2% over the state-of-the-art solution, while outperforming individual GPU and quad-core CPU executions by more than 2 and 5 times, respectively. Index Terms-General-purpose computation on graphics processing units, heterogeneous systems, load balancing, video coding.

Proceedings of the 1999 International Conference on Parallel Processing, 1999

Soft-real time applications, such as continuous media CM systems, have an important property, namely, they allow for graceful adaptation of the application Quality-of-Service QoS, and therefore are able to have acceptable performance with reduced resource utilization. This can be used by the admission control process to decide if an application can be admitted, even if the resource is congested. In this paper, we present a Soft-QoS framework for Continuous Media servers, which provides a dynamic and adaptive admission control and scheduling algorithm. Using our policy, we could increase the number of simultaneously running clients that could be supported and could ensure a g o od r esponse ratio and better resource utilization under heavy tra c requirements. The observations and ndings from the model are validated with simulation studies.

A distributed real-time or embedded system consists of a large number of applications that interact with the physical environment and must satisfy end-to-end timing constraints. Applications in such system may offer different quality levels (such as higher or lower frame rates for a video conferencing application) across multiple factors or dimensions (such as frame rate, resolution). The end-user derives different degrees of satisfaction (known as utility) from these quality levels.

2003

Abstract—This paper presents the embedded realization and experimental evaluation of a media stream scheduler on Network Interface (NI) CoProcessor boards. When using media frames as scheduling units, the scheduler is able to operate in real-time on streams traversing the CoProcessor, resulting in its ability to stream video to remote clients at real-time rates. The contributions of this paper are its detailed evaluation of the effects of placing application or kernel-level functionality, like packet scheduling on NIs, rather than the host machines to which they are attached. The main benefits of such placement are 1) that traffic is eliminated from the host bus and memory subsystem, thereby allowing increased host CPU utilization for other tasks, and 2) that NI-based scheduling is immune to host-CPU loading, unlike host-based media schedulers that are easily affected even by transient load conditions. An outcome of this work is a proposed cluster architecture for building scalable ...

ACM Transactions on Embedded Computing Systems, 2011

We propose an adaptive scheduling technique to schedule highly dynamic multimedia tasks on a CPU. We use a combination of two techniques: the first one is a feedback mechanism to track the resource requirements of the tasks based on "local" observations. The second one is a mechanism that operates with a "global" visibility, reclaiming unused bandwidth. The combination proves very effective: resource reclaiming increases the robustness of the feedback, while the identification of the correct bandwidth made by the feedback increases the effectiveness of the reclamation. We offer both theoretical results and an extensive experimental validation of the approach.

Proceedings. Eighth IEEE Real-Time and Embedded Technology and Applications Symposium

In constant-bandwidth server (CBS) systems, several different applications are executed upon a shared computing platform in such a manner that each application seems to be executing on a slower dedicated processor. CBS systems have thus far only been implemented upon uniprocessors; here, a multiprocessor extension, which can be implemented upon computing platforms comprised of several identical preemptable processors, is proposed and proven correct.

IEEE Transactions on Circuits and Systems for Video Technology, 2000

State of the art digital video compression produces bursty, variable bit rate video. The bursty nature of compressed video raises challenges in the design of video servers. In this paper, we first present a method for the efficient retrieval of bursty video data from the disk system to the memory of a digital video server. For a single video stream, the proposed retrieval schedule minimizes the buffer requirement for continuous retrieval, given that a fixed disk bandwidth is reserved for the entire duration of retrieval. Secondly, we present an optimal resource reservation algorithm for multiple video streams based on the proposed retrieval schedule. The resource reservation algorithm maximizes the number of bursty video streams that can be supported by a video server, given any disk bandwidth and memory resource. Thirdly, we present a progressive display scheme for scalable video that is based on the retrieval schedule and resource reservation algorithm. Performance evaluations based on simulations using MPEG-2 trace data are presented. For a PC with four disks and a memory resource of 120 MBytes, our approach can support 50%-275% more video streams than previously proposed approaches, depending on the pre-fetch delay that users are willing to tolerate in interactive viewing of videos.

2010

The problem of scheduling a set of tasks on a multiprocessor architecture is addressed. Tasks are assumed to be sporadic with arbitrary deadlines and may migrate between processors. The execution of migrating tasks is controlled by a bandwidth reservation scheme so that schedulability is guaranteed by EDF. Task migration costs are taken into consideration. Results from experiments indicate that the proposed approach performs well in terms of schedulability.