ARC: A Bottom-Up Approach to Negotiated QoS

Mobile systems operate in a resource-scarce environment and thus must adapt to external conditions; all layers must make cost-based decisions about what mode of operation to use in response to performance feedback. This paper focuses on the generic interface between adjacent layers (client and server) in a multi-level hierarchy. The Adaptive Research Contracts (ARC) framework uses a bottom-up approach in which the server exposes a range of quality/cost modes to the client above. This allows the client to trade off various algorithms generating different workloads for multiple resources. A case study shows that control can be distributed effectively over multiple layers with ARC; global cost-effective solutions can be obtained by exchanging a small fraction of all possible control settings

Design space analysis for modeling incentives in distributed systems

Distributed systems without a central authority, such as peer-to-peer (P2P) systems, employ incentives to encourage nodes to follow the prescribed protocol. Game theoretic analysis is often used to evaluate incentives in such systems. However, most game-theoretic analyses of distributed systems do not adequately model the repeated interactions of nodes inherent in such systems. We present a game-theoretic analysis of a popular P2P protocol, Bit-Torrent, that models the repeated interactions in such protocols. We also note that an analytical approach for modeling incentives is often infeasible given the complicated nature of most deployed protocols. In order to comprehensively model incentives in complex protocols, we propose a simulation-based method, which we call Design Space Analysis (DSA). DSA provides a tractable analysis of competing protocol variants within a detailed design space. We apply DSA to P2P file swarming systems. With extensive simulations we analyze a wide-range of protocol variants and gain insights into their robustness and performance. To validate these results and to demonstrate the efficacy of DSA, we modify an instrumented BitTorrent client and evaluate protocols discovered using DSA. We show that they yield higher system performance and robustness relative to the reference implementation

SP@CE - An SP-Based Programming Model for Consumer Electronics Streaming Applications

Abstract. Consumer Electronics (CE) devices are becoming the favorite target platforms for multimedia streaming applications, but finding the right solutions for efficient programming, both in terms of development time and application performance is not trivial. In this context, we presen

Aristotle: A performance impact indicator for the OpenCL kernels using local memory

Due to the increasing complexity of multi/many-core architectures (with their mix of caches and scratch-pad memories) and applications (with different memory access patterns), the performance of many workloads becomes increasingly variable. In this work, we address one of the main causes for this performance variability: the efficiency of the memory system. Specifically, based on an empirical evaluation driven by memory access patterns, we qualify and partially quantify the performance impact of using local memory in multi/many-core processors. To do so, we systematically describe memory access patterns (MAPs) in an application-agnostic manner. Next, for each identified MAP, we use OpenCL (for portability reasons) to generate two microbenchmarks: a "naive" version (without local memory) and "an optimized" version (using local memory). We then evaluate both of them on typically used multi-core and many-core platforms, and we log their performance. What we eventually obtain is a local memory performance database, indexed by various MAPs and platforms. Further, we propose a set of composing rules for multiple MAPs. Thus, we can get an indicator of whether using local memory is beneficial in the presence of multiple memory access patterns. This indication can be used to either avoid the hassle of implementing optimizations with too little gain or, alternatively, give a rough prediction of the performance gain

The Globe Infrastructure Directory Service

To implement adaptive replication strategies for Web documents, we have developed a wide area resource management system. This system allows servers to be managed on a local and global level. On a local level the system manages information about the resources and services provided by the servers, while on a global level the system allows servers to be searched for, added to, and removed from the system. As part of the system, and also in order to implement adaptive replication strategies, we introduce a hierarchical location representation for network elements such as servers, objects, and clients. This location representation allows us to easily and efficiently find and group network elements based on their location in a worldwide network. Our resource management system can be implemented using standard Internet technologies and has a broader range of applications besides making adaptive replication strategies possible for Web documents

Analysis of local enumeration and storage schemes in HPF

In this paper, we analyze the properties and efficiency of three basic local enumeration and three storage compression schemes for cyclic(m) data distributions in High Performance Fortran (HPF). The methods are presented in a unified framework, showing the relations between the various methods. We show that for array accesses that are affine functions of the loop bounds, efficient local enumeration and storage compression schemes can be derived. Furthermore, the basic set enumeration and storage techniques are shown to be orthogonal, if the local storage compression scheme is collapsible. This allows choosing the most appropriate method in parts of the computation and communication phases of parallel loops. Performance figures of the methods show that programs with cyclic(m) data distributions can be executed efficiently even without compile-time knowledge of the relevant access, alignment, and distribution parameters