7770599
Improving soft real-time performance through better slack reclaiming
Modern operating systems frequently support applications with a variety of timing constraints including hard real-time, soft real-time, and best-effort. To guarantee performance, critical applications typically over-reserve resources based on worst-case resource usage estimates, while others may reserve based on average-case or other estimates. When resources are fully subscribed, the performance of soft- and non-real-time applications depends upon the effective distribution of dynamic slack - reserved, but unused resources - from other tasks. Motivated by several representative examples, we derive four general principles for the effective management of slack. We have implemented these principles in four progressively better slack schedulers that demonstrate their effectiveness. BACKSLASH, which employs all four principles, misses fewer soft realtime deadlines than all of the other slack schedulers we examined
7754068
Optimal state feedback based resource allocation for resource-constrained control tasks
In many application areas, including control systems, careful management of system resources is key to providing the best application performance. Most traditional resource management techniques for real-time systems with multiple control loops are based on open-loop strategies that statically allocate a constant CPU share to each controller, independent of their current resource needs. This provides average control performance with minimal overhead but in general fails to provide the best performance possible within the available resources. We show that by using feedback to dynamically allocate resources to controllers as a function of the current state of their controlled systems, control performance can be significantly improved. We present an optimal resource allocation policy that maximizes control performance within the available resources and provide experimental results showing that the optimal policy 1) significantly increases control performance compared to traditional control system implementations (by more than 20% in our experiments), 2) maximizes control performance over other feedback-based policies, 3) saves resources when perturbations occur infrequently, and 4) incurs negligible overhead.
5057977
ZPL: A Machine Independent Programming Language for Parallel Computers
The goal of producing architecture-independent parallel programs is complicated by the competing need for high performance. The ZPL programming language achieves both goals by building upon an abstract parallel machine and by providing programming constructs that allow the programmer to "see" this underlying machine. This paper describes ZPL and provides a comprehensive evaluation of the language with respect to its goals of performance, portability, and programming convenience. In particular, we describe ZPt's machine-independent performance model, describe the programming benefits of ZPL's region-based constructs, summarize the compilation benefits of the language's high-level semantics, and summarize empirical evidence that ZPL has achieved both high performance and portability on diverse machines such as the IBM SP-2, Cray T3E, and SGI Power Challenge.
11960535
Performance Modeling of Grid Resource Management and Scheduling Systems
Performance evaluation of grid resource management and scheduling system is of key importance to the success of the grid. In this paper, we introduce a generalized stochastic Petri net (GSPN) model for such purpose. The model is simple with clarity and can be applied to other research issues on grid to provide them with performance evaluation capabilities.
9988109
An Adaptive Distance Learning System Based on Media Streaming
This paper presents the design and development of an adaptive real-time multimedia distance learning system:EasyLearning®, which supports both online learning and courseware on demand through the Internet. By combining the innovative ideas and best features of scalable video coding, screen share algorithm, session control signaling, and TCP-friendly multicast protocol, EasyLearning® is capable of achieving good Quality of Service (QoS) of video and audio, efficiency, and reliability of media delivery. According to the experimental comparison between EasyLearning® and Microsoft media service based system (MMS), Easylearning® provides better performance.
13476763
CPU/power-constrained mobile devices
Due to the limited processing capability, memory constraints, and the power budget of mobile clients, multimedia coders and/or decoders are often difficult to implement on wireless handheld PDAs. In this Universal Tuner project, we designed and implemented a wireless video streaming system that transcodes MPEG-1/2 videos or live TV broadcasting videos to the BW or indexed color Palm OS devices. In our system, the complexity of multimedia compression and decompression algorithms is adaptively partitioned between the encoder and decoder. A mobile client would selectively disable or reenable stages of the algorithm to adapt to the device's effective processing capability. Our variable-complexity strategy of selective disabling of modules supports graceful degradation of the complexity of multimedia coding and decoding into a mobile client's low-power mode, i.e. the clock frequency of its next-generation low power CPU has been scaled down to conserve power. We modified the structure of the standard motion-compensated DCT video codecs to implement a simplified the encoder on a PC server and the decoder on a complexity-constrained PDA viewing client.
43707062
A Dependable Task Scheduling Strategy for a Fault Tolerant Grid Model
Grid provides an integrated computer platform composed of differentiated and distributed systems. In this paper, aiming at the heterogeneity and dynamism of a grid system, a novel fault-tolerant grid-scheduling model is presented based on Stochastic Petri Net. On the other hand, a new grid-scheduling strategy, the united strategy for the availability factor and expected accomplishing time (USAT), is put forward, In the end, the performance of the scheduling strategy based on the fault-tolerant grid-scheduling model is analyzed by SPNP software package. The numerical results show that USAT strategy can reduce these bad effects of dynamic and autonomic resources to some extent so as to guarantee quality of service (QoS).