Design of an optical packet switch for real-time applications

Network switches are typically designed for best- effort Internet traffic. Most of existing studies have been focused on improving throughput and delay performance in an average sense rather than providing guaranteed delay bound that is critical for real-time applications. It has not been fully investigated how to design an efficient packet switching algorithm for real-time applications. In this paper, we propose a design framework for a real-time optical switch that is intended for use as an optical switch fabric. Our contributions are two folds: First, by introducing a clearance-time optimal switching together with clock-based scheduling, our switching design guarantees any feasible real-time traffic to be switched in two- clock periods. Second, we investigate key implementation issues of an optical packet switch such as packet size and buffering for real-time applications, and take account of these issues in design and performance evaluation of a switching algorithm. Our numerical study shows that the proposed switching algorithm provides a larger schedulability region with significantly reduced delay compared to the well-known iSLIP scheme. © 2012 IEEE

ClusterFetch: A lightweight prefetcher for general workloads

Application loading times can be reduced by prefetching disk blocks into the buffer cache. Existing prefetching schemes for general workloads suffer from significant overheads and low accuracy. ClusterFetch is a lightweight prefetcher that identifies continuous sequences of I/O requests and identifies the files that trigger them. The next time that the same files are opened, the corresponding disk blocks are prefetched. In experiments, ClusterFetch reduced the launch time, by which we refer to the latency that occurs when a programfirst runs, by 15.2 to 30.9%, and loading times, meaning the delays that are incurred while additional data is loaded from the disk during program execution, by 15.9%. Copyright © 2015 AC

File-system-level flash caching for improving application launch time on logical hybrid disks

Application launch time is an important performance metric to user experience in desktop environment. The launch time mostly depends on the performance of secondary storage. There is a cost-performance trade-off in using hard disk drive (HDD) or solid-state drive (SSD). Thus, application launch times can be reduced by utilizing SSDs as caches for slow HDDs. We propose a new SSD caching scheme which migrates data blocks from HDDs to SSDs. Since our scheme operates entirely in the file system level and does not require an extra layer for mapping SSD-cached data, which is essential in most other schemes, our scheme does not incur mapping overheads that cause significant burdens on main memory, CPU, and SSD cache itself. Experimental results demonstrate our scheme yields 56% of performance gain in application launch

Guaranteeing the End-to-End Latency of an IMA System with an Increasing Workload

New features are often added incrementally to avionics systems to minimize the need for redesign and recertification. However, it then becomes necessary to check that the timing constraints of existing as well as new applications are met. We facilitate these checks by introducing a new data switch that bounds the latency of end-to-end communications across a network. This switch runs a clock-driven switching algorithm that is throughput-optimal with a bounded worst-case delay for all feasible traffic. We propose associated heuristics that determine whether the timing constraints of an integrated modular avionics (IMA) system network that uses this switch are met, even if new features have caused traffic to increase, and then search for alternative network configurations if necessary. Virtual integration is used to make a combined analysis of the worst-case delay in the network and the local buses of individual computing modules. This analysis considers the shared network topology, local hardware architectures, and specified IMA configurations. Our approach can be used by a system architect as an effective method for quickly determining which possible system architectures should be pursued to meet timing constraints, and it allows the cascading effects of changes to be tracked and managed. We demonstrate how these heuristics work through an example in which changes are made to an environmental monitoring facility within an avionics system that uses our switch. © 2013 IEEE.