1,436 research outputs found
Architecture for Cooperative Prefetching in P2P Video-on- Demand System
Most P2P VoD schemes focused on service architectures and overlays
optimization without considering segments rarity and the performance of
prefetching strategies. As a result, they cannot better support VCRoriented
service in heterogeneous environment having clients using free VCR controls.
Despite the remarkable popularity in VoD systems, there exist no prior work
that studies the performance gap between different prefetching strategies. In
this paper, we analyze and understand the performance of different prefetching
strategies. Our analytical characterization brings us not only a better
understanding of several fundamental tradeoffs in prefetching strategies, but
also important insights on the design of P2P VoD system. On the basis of this
analysis, we finally proposed a cooperative prefetching strategy called
"cooching". In this strategy, the requested segments in VCR interactivities are
prefetched into session beforehand using the information collected through
gossips. We evaluate our strategy through extensive simulations. The results
indicate that the proposed strategy outperforms the existing prefetching
mechanisms.Comment: 13 Pages, IJCN
Prefetching and Caching Techniques in File Systems for Mimd Multiprocessors
The increasing speed of the most powerful computers, especially multiprocessors, makes it difficult to provide sufficient I/O bandwidth to keep them running at full speed for the largest problems. Trends show that the difference in the speed of disk hardware and the speed of processors is increasing, with I/O severely limiting the performance of otherwise fast machines. This widening access-time gap is known as the βI/O bottleneck crisis.β One solution to the crisis, suggested by many researchers, is to use many disks in parallel to increase the overall bandwidth. \par This dissertation studies some of the file system issues needed to get high performance from parallel disk systems, since parallel hardware alone cannot guarantee good performance. The target systems are large MIMD multiprocessors used for scientific applications, with large files spread over multiple disks attached in parallel. The focus is on automatic caching and prefetching techniques. We show that caching and prefetching can transparently provide the power of parallel disk hardware to both sequential and parallel applications using a conventional file system interface. We also propose a new file system interface (compatible with the conventional interface) that could make it easier to use parallel disks effectively. \par Our methodology is a mixture of implementation and simulation, using a software testbed that we built to run on a BBN GP1000 multiprocessor. The testbed simulates the disks and fully implements the caching and prefetching policies. Using a synthetic workload as input, we use the testbed in an extensive set of experiments. The results show that prefetching and caching improved the performance of parallel file systems, often dramatically
Performance of SSE and AVX Instruction Sets
SSE (streaming SIMD extensions) and AVX (advanced vector extensions) are SIMD
(single instruction multiple data streams) instruction sets supported by recent
CPUs manufactured in Intel and AMD. This SIMD programming allows parallel
processing by multiple cores in a single CPU. Basic arithmetic and data
transfer operations such as sum, multiplication and square root can be
processed simultaneously. Although popular compilers such as GNU compilers and
Intel compilers provide automatic SIMD optimization options, one can obtain
better performance by a manual SIMD programming with proper optimization: data
packing, data reuse and asynchronous data transfer. In particular, linear
algebraic operations of vectors and matrices can be easily optimized by the
SIMD programming. Typical calculations in lattice gauge theory are composed of
linear algebraic operations of gauge link matrices and fermion vectors, and so
can adopt the manual SIMD programming to improve the performance.Comment: 7 pages, 5 figures, 4 tables, Contribution to proceedings of the 30th
International Symposium on Lattice Field Theory (Lattice 2012), June 24-29,
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