1,227 research outputs found
Increasing throughput in IEEE 802.11 by optimal selection of backoff parameters
Engineering and Physical Sciences Research Council. Grant Number: EP/G012628/
Quality-of-service management in IP networks
Quality of Service (QoS) in Internet Protocol (IF) Networks has been the subject of
active research over the past two decades. Integrated Services (IntServ) and
Differentiated Services (DiffServ) QoS architectures have emerged as proposed
standards for resource allocation in IF Networks. These two QoS architectures
support the need for multiple traffic queuing systems to allow for resource
partitioning for heterogeneous applications making use of the networks. There have
been a number of specifications or proposals for the number of traffic queuing
classes (Class of Service (CoS)) that will support integrated services in IF Networks,
but none has provided verification in the form of analytical or empirical investigation
to prove that its specification or proposal will be optimum.
Despite the existence of the two standard QoS architectures and the large volume of
research work that has been carried out on IF QoS, its deployment still remains
elusive in the Internet. This is not unconnected with the complexities associated with
some aspects of the standard QoS architectures. [Continues.
PARALLELIZING TIME-SERIES SESSION DATA ANALYSIS WITH A TYPE-ERASURE BASED DSEL
The Science Information Network (SINET) is a Japanese academic backbone network. SINET consists of more than 800 universities and research institutions. In the operation of a huge academic backbone network, more flexible querying technology is required to cope with massive time series session data and analysis of sophisticated cyber-attacks. This paper proposes a parallelizing DSEL (Domain Specific Embedded Language) processing for huge time-series session data. In our DESL, the function object is implemented by type erasure for constructing internal DSL for processing time-series data. Type erasure enables our parser to store function pointer and function object into the same *void type with class templates. We apply to scatter/gather pattern for concurrent DSEL parsing. Each thread parses DSEL to extract the tuple timestamp, source IP, and destination IP in the gather phase. In the scattering phase, we use a concurrent hash map to handle multiple thread outputs with our DSEL.
In the experiment, we have measured the elapsed time in parsing and inserting IPv4 address and timestamp data format ranging from 1,000 to 50,000 lines with 24-row items. We have also measured CPU idle time in processing 100,000,000 lines of session data with 5, 10 and 20 multiple threads. It has been turned out that the proposed method can work in feasible computing time in both cases
ATAMM enhancement and multiprocessing performance evaluation
The algorithm to architecture mapping model (ATAAM) is a Petri net based model which provides a strategy for periodic execution of a class of real-time algorithms on multicomputer dataflow architecture. The execution of large-grained, decision-free algorithms on homogeneous processing elements is studied. The ATAAM provides an analytical basis for calculating performance bounds on throughput characteristics. Extension of the ATAMM as a strategy for cyclo-static scheduling provides for a truly distributed ATAMM multicomputer operating system. An ATAAM testbed consisting of a centralized graph manager and three processors is described using embedded firmware on 68HC11 microcontrollers
Performance by Unified Model Analysis (PUMA)
Evaluation of non-functional properties of a design (such as performance, dependability, security, etc.) can be enabled by design annotations specific to the property to be evaluated. Performance properties, for instance, can be annotated on UML designs by using the UML Profile for Schedulability, Performance and Time (SPT) . However the communication between the design description in UML and the tools used for non-functional properties evaluation requires support, particularly for performance where there are many alternative performance analysis tools that might be applied. This paper describes a tool architecture called PUMA, which provides a unified interface between different kinds of design information and different kinds of performance models, for example Markov models, stochastic Petri nets and process algebras, queues and layered queues. The paper concentrates on the creation of performance models. The unified interface of PUMA is centered on an intermediate model called Core Scenario Model (CSM), which is extracted from the annotated design model. Experience shows that CSM is also necessary for cleaning and auditing the design information, and providing default interpretations in case it is incomplete, before creating a performance model
Predictive analysis and optimisation of pipelined wavefront applications using reusable analytic models
Pipelined wavefront computations are an ubiquitous class of high performance parallel algorithms
used for the solution of many scientific and engineering applications. In order to aid
the design and optimisation of these applications, and to ensure that during procurement platforms
are chosen best suited to these codes, there has been considerable research in analysing
and evaluating their operational performance.
Wavefront codes exhibit complex computation, communication, synchronisation patterns,
and as a result there exist a large variety of such codes and possible optimisations. The
problem is compounded by each new generation of high performance computing system,
which has often introduced a previously unexplored architectural trait, requiring previous
performance models to be rewritten and reevaluated.
In this thesis, we address the performance modelling and optimisation of this class of
application, as a whole. This differs from previous studies in which bespoke models are applied
to specific applications. The analytic performance models are generalised and reusable,
and we demonstrate their application to the predictive analysis and optimisation of pipelined
wavefront computations running on modern high performance computing systems.
The performance model is based on the LogGP parameterisation, and uses a small
number of input parameters to specify the particular behaviour of most wavefront codes. The
new parameters and model equations capture the key structural and behavioural differences
among different wavefront application codes, providing a succinct summary of the operations
for each application and insights into alternative wavefront application design.
The models are applied to three industry-strength wavefront codes and are validated
on several systems including a Cray XT3/XT4 and an InfiniBand commodity cluster. Model
predictions show high quantitative accuracy (less than 20% error) for all high performance
configurations and excellent qualitative accuracy.
The thesis presents applications, projections and insights for optimisations using the
model, which show the utility of reusable analytic models for performance engineering of
high performance computing codes. In particular, we demonstrate the use of the model for:
(1) evaluating application configuration and resulting performance; (2) evaluating hardware
platform issues including platform sizing, configuration; (3) exploring hardware platform design
alternatives and system procurement and, (4) considering possible code and algorithmic
optimisations
Web page performance analysis
Computer systems play an increasingly crucial and ubiquitous role in human endeavour by carrying out or facilitating tasks and providing information and services. How much work these systems can accomplish, within a certain amount of time, using a certain amount of resources, characterises the systemsā performance, which is a major concern when the systems are planned, designed, implemented, deployed, and evolve. As one of the most popular computer systems, the Web is inevitably scrutinised in terms of performance analysis that deals with its speed, capacity, resource utilisation, and availability. Performance analyses for the Web are normally done from the perspective of the Web servers and the underlying network (the Internet). This research, on the other hand, approaches Web performance analysis from the perspective of Web pages. The performance metric of interest here is response time. Response time is studied as an attribute of Web pages, instead of being considered purely a result of network and server conditions. A framework that consists of measurement, modelling, and monitoring (3Ms) of Web pages that revolves around response time is adopted to support the performance analysis activity. The measurement module enables Web page response time to be measured and is used to support the modelling module, which in turn provides references for the monitoring module. The monitoring module estimates response time. The three modules are used in the software development lifecycle to ensure that developed Web pages deliver at worst satisfactory response time (within a maximum acceptable time), or preferably much better response time, thereby maximising the efficiency of the pages. The framework proposes a systematic way to understand response time as it is related to specific characteristics of Web pages and explains how individual Web page response time can be examined and improved
Modelling of Information Flow and Resource Utilization in the EDGE Distributed Web System
The adoption of Distributed Web Systems (DWS) into modern engineering design process has dramatically increased in recent years. The Engineering Design Guide and Environment (EDGE) is one such DWS, intended to provide an integrated set of tools for use in the development of new products and services. Previous attempts to improve the efficiency and scalability of DWS focused largely on hardware utilization (i.e. multithreading and virtualization) and software scalability (i.e. load balancing and cloud services). However, these techniques are often limited to analysis of the computational complexity of the algorithms implemented.
This work seeks to improve the understanding of efficiency and scalability of DWS by modelling the dynamics of information flow and resource utilization by characterizing DWS workloads through historical usage data (i.e. request type, frequency, access time). The design and implementation of EDGE is described. A DWS model of an EDGE system is developed and validated against theoretical limiting cases. The DWS model is used to predict the throughput of an EDGE system given a resource allocation and workflow. Results of the simulation suggest that proposed DWS designs can be evaluated according to the usage requirements of an engineering firm, ultimately guiding an informed decision for the selection and deployment of a DWS in an enterprise environment. Recommendations for future work related to the continued development of EDGE, DWS modelling of EDGE installation environments, and the extension of DWS modelling to new product development processes are presented
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