CSP methods for identifying atomic actions in the design of fault tolerant concurrent systems

Limiting the extent of error propagation when faults occur and localizing the subsequent error recovery are common concerns in the design of fault tolerant parallel processing systems, Both activities are made easier if the designer associates fault tolerance mechanisms with the underlying atomic actions of the system, With this in mind, this paper has investigated two methods for the identification of atomic actions in parallel processing systems described using CSP, Explicit trace evaluation forms the basis of the first algorithm, which enables a designer to analyze interprocess communications and thereby locate atomic action boundaries in a hierarchical fashion, The second method takes CSP descriptions of the parallel processes and uses structural arguments to infer the atomic action boundaries. This method avoids the difficulties involved with producing full trace sets, but does incur the penalty of a more complex algorithm

Distributed real-time operating system (DRTOS) modeling in SpecC

System level design of an embedded computing system involves a multi-step process to refine the system from an abstract specification to an actual implementation by defining and modeling the system at various levels of abstraction. System level design supports evaluating and optimizing the system early in design exploration.;Embedded computing systems may consist of multiple processing elements, memories, I/O devices, sensors, and actors. The selection of processing elements includes instruction-set processors and custom hardware units, such as application specific integrated circuit (ASIC) and field programmable gate array (FPGA). Real-time operating systems (RTOS) have been used in embedded systems as an industry standard for years and can offer embedded systems the characteristics such as concurrency and time constraints. Some of the existing system level design languages, such as SpecC, provide the capability to model an embedded system including an RTOS for a single processor. However, there is a need to develop a distributed RTOS modeling mechanism as part of the system level design methodology due to the increasing number of processing elements in systems and to embedded platforms having multiple processors. A distributed RTOS (DRTOS) provides services such as multiprocessor tasks scheduling, interprocess communication, synchronization, and distributed mutual exclusion, etc.;In this thesis, we develop a DRTOS model as the extension of the existing SpecC single RTOS model to provide basic functionalities of a DRTOS implementation, and present the refinement methodology for using our DRTOS model during system level synthesis. The DRTOS model and refinement process are demonstrated in the SpecC SCE environment. The capabilities and limitations of the DRTOS modeling approach are presented

Automatic User Interaction Detection and Scheduling with RSIO

Response time is one of the most important factors for the overall usability of a computer system. We present RSIO, a processor scheduling framework for improving the response time of latency-sensitive applications by monitoring accesses to I/O channels and inferring when user interactions occur. RSIO provides a general mechanism for all user interactions, including direct interactions via local HCI devices such as mouse and keyboard, indirect interactions through middleware, and remote interactions through networks. It automatically and dynamically identifies processes involved in a user interaction and boosts their priorities at the time the interaction occurs to improve system response time. RSIO detects processes that directly handle a user interaction as well as those indirectly involved in processing the interaction, automatically accounting for dependencies and boosting their priorities accordingly. RSIO works with existing schedulers, processes that may mix interactive and batch activities, and requires no application modifications to identify periods of latency-sensitive application activity. We have implemented RSIO in Linux and measured its effectiveness on microbenchmarks and real applications. Our results show that RSIO is easy to use and can provide substantial improvements in system performance for latency-sensitive applications

Parallel processing for scientific computations

The main contribution of the effort in the last two years is the introduction of the MOPPS system. After doing extensive literature search, we introduced the system which is described next. MOPPS employs a new solution to the problem of managing programs which solve scientific and engineering applications on a distributed processing environment. Autonomous computers cooperate efficiently in solving large scientific problems with this solution. MOPPS has the advantage of not assuming the presence of any particular network topology or configuration, computer architecture, or operating system. It imposes little overhead on network and processor resources while efficiently managing programs concurrently. The core of MOPPS is an intelligent program manager that builds a knowledge base of the execution performance of the parallel programs it is managing under various conditions. The manager applies this knowledge to improve the performance of future runs. The program manager learns from experience

A model of time dependent behavior in concurrent software systems

A great difficulty in building distributed systems lies in being able to predict what the systems behavior will be. A distributed or communicating system is defined here to be one in in which the hardware consists of a set of processors each with their own memory, connected by some communication medium (there is no shared memory), and the software is assumed to be of the CSP (Hoare's Communicating Sequential Processes) type.In the past few years some theories have been proposed to model features of communicating systems. Milner's Calculus of communicating Systems (CCS), Winskel's Synchronization Trees (ST), Hennessy's Acceptance Trees (AT), and Hoare and Brookes's theory of communicating processes are examples of formal models of such systems. All of these models concentrate on modelling observable properties of a system.Event Dependency Trees (EDT) is a new representation of communicating systems that models the time dependent nature of such systems. None of the representations mentioned above explicitly represent time but time is precisely the factor that introduces so much variability and complexity into such software and systems. EDT provides a representation based on trees and a set of operations over the EDT trees that can be used to produce deadlock-free software. The model supplies potentially important information for the design and construction of distributed, parallel software systems

Efficient processor management strategies for multicomputer systems

Multicomputers are cost-effective alternatives to the conventional supercomputers. Contemporary processor management schemes tend to underutilize the processors and leave many of the processors in the system idle while jobs are waiting for execution;Instead of designing faster processors or interconnection networks, a substantial performance improvement can be obtained by implementing better processor management strategies. This dissertation studies the performance issues related to the processor management schemes and proposes several ways to enhance the multicomputer systems by means of processor management. The proposed schemes incorporate the concepts of size-reduction, non-contiguous allocation, as well as job migration. Job scheduling using a bypass-queue is also studied. All the proposed schemes are proven effective in improving the system performance via extensive simulations. Each proposed scheme has different implementation cost and constraints. In order to take advantage of these schemes, judicious selection of system parameters is important and is discussed

3D Mapping of indoor environments using RGB-D Kinect camera for robotic mobile application

RGB-D cameras are new, low cost, sensors that provide depth information for every RGB pixel acquired. Combining this information, it is possible to develop 3D perception in an indoor environment. In this paper we investigate how this technology can be used for building 3D maps. Such maps can gain more importance in the context of mobile robotics, as it can be used for many applications such as robot navigation. We present how, knowing the robot's pose, it is possible to build such maps and extract useful information like recognize objects and determine their position within the map.Outgoin

Automatic User Interaction Detection and Scheduling with RSIO

Response time is one of the most important factors for the overall usability of a computer system. We present RSIO, a processor scheduling framework for improving the response time of latency-sensitive applications by monitoring accesses to I/O channels and inferring when user interactions occur. RSIO provides a general mechanism for all user interactions, including direct interactions via local HCI devices such as mouse and keyboard, indirect interactions through middleware, and remote interactions through networks. It automatically and dynamically identifies processes involved in a user interaction and boosts their priorities at the time the interaction occurs to improve system response time. RSIO detects processes that directly handle a user interaction as well as those indirectly involved in processing the interaction, automatically accounting for dependencies and boosting their priorities accordingly. RSIO works with existing schedulers, processes that may mix interactive and batch activities, and requires no application modifications to identify periods of latency-sensitive application activity. We have implemented RSIO in Linux and measured its effectiveness on microbenchmarks and real applications. Our results show that RSIO is easy to use and can provide substantial improvements in system performance for latency-sensitive applications