Simultaneous Requests Research Articles

A priority-based polling scheduling algorithm for arbitration policy in Network on Chip

A solution is imperatively expected to meet the efficient contention resolution schemes for managing simultaneous access requests to the communication resources on the Network on Chip (NoC). Based on the ideas of conflict-free transmission, priority-based service, and dynamic self-adaptation to loading, this paper presents a novel scheduling algorithm for Medium Access Control (MAC) in NoC with the researches of the communication structure features of 2D mesh. The algorithm gives priority to guarantee the Quality of Service (QoS) for local input port as well as dynamic adjustment of the performance of the other ports along with input load change. The theoretical model of this algorithm is established with Markov chain and probability generating function. Mathematical analysis is made on the mean queue length and the mean inquiry cyclic time of the system. Simulated experiments are conducted to test the accuracy of the model. It turns out that the findings from theoretical analysis correspond well with those from simulated experiments. Further more, the analytical findings of the system performance demonstrate that the algorithm enables effectively strengthen the fairness and stability of data transmissions in NoC.

Link Stress Reduction against Bursty Arrivals of Content Requests

Content delivery networks are designed to extend the end-to-end transport capability of the Internet to cope with increases in video traffic. For further improvement, bursty request arrivals should be efficiently addressed. As opposed to previous approaches, in which the best client-server pair is individually selected (individual optimization), this paper proposes an algorithm for dealing with simultaneous arrival requests, in which client-server pairs are selected such that all requests receive good service (social optimization). The performance of the proposed algorithm is compared with that of the closest algorithm, an individual optimization algorithm, under the condition that a large number of requests arrive simultaneously. The evaluation criterion is the worst link stress, which is the largest number of streams per link. The numerical results show that the proposed algorithm is effective for large-scale networks and that the closest algorithm does not provide near-optimal solutions, especially when all requests arrive in a small part of the network or when there are many servers.

Scalability of write-ahead logging on multicore and multisocket hardware

The shift to multi-core and multi-socket hardware brings new challenges to database systems, as the software parallelism determines performance. Even though database systems traditionally accommodate simultaneous requests, a multitude of synchronization barriers serialize execution. Write-ahead logging is a fundamental, omnipresent component in ARIES-style concurrency and recovery, and one of the most important yet-to-be addressed potential bottlenecks, especially in OLTP workloads making frequent small changes to data. In this paper, we identify four logging-related impediments to database system scalability. Each issue challenges different level in the software architecture: (a) the high volume of small-sized I/O requests may saturate the disk, (b) transactions hold locks while waiting for the log flush, (c) extensive context switching overwhelms the OS scheduler with threads executing log I/Os, and (d) contention appears as transactions serialize accesses to in-memory log data structures. We demonstrate these problems and address them with techniques that, when combined, comprise a holistic, scalable approach to logging. Our solution achieves a 20–69% speedup over a modern database system when running log-intensive workloads, such as the TPC-B and TATP benchmarks, in a single-socket multiprocessor server. Moreover, it achieves log insert throughput over 2.2 GB/s for small log records on the single-socket server, roughly 20 times higher than the traditional way of accessing the log using a single mutex. Furthermore, we investigate techniques on scaling the performance of logging to multi-socket servers. We present a set of optimizations which partly ameliorate the latency penalty that comes with multi-socket hardware, and then we investigate the feasibility of applying a distributed log buffer design at the socket level.

Hardware Accelerated Impairment-Aware Control Plane for Future Optical Networks

In this letter, a hardware accelerated GMPLS based and impairment-aware control plane suitable for optical networks with concurrent lightpath requests support is proposed and evaluated. It outperforms the software version by 80 times in the order of sub-seconds. The high acceleration rate, simultaneous requests support, scalability and low computation time variance are the key features of this tool.

Heuristic Algorithm for Priority Traffic Signal Control

A heuristic algorithm is presented for traffic signal control with simultaneous multiple priority requests at isolated intersections in the context of vehicle-to-infrastructure communications being available on priority vehicles, such as emergency vehicles and transit buses. This heuristic algorithm can achieve near-optimal signal timing when all simultaneous requests are considered and can be visualized in a phase–time diagram. First, the problem with the control of multiple priority traffic signals is transformed into a network cut problem that is polynomial solvable under some reasonable assumptions. Second, a phase–time diagram is presented to visualize and evaluate priority delay given a signal plan and a collection of priority request arrival times. Microscopic traffic simulation is used to compare the heuristic with the state-of-the-practice algorithms for transit signal priority. The proposed heuristic algorithm could reduce average bus delay in congested conditions by about 50%, especially with a high frequency of conflicting priority requests.

Aether

The shift to multi-core hardware brings new challenges to database systems, as the software parallelism determines performance. Even though database systems traditionally accommodate simultaneous requests, a multitude of synchronization barriers serialize execution. Write-ahead logging is a fundamental, omnipresent component in ARIES-style concurrency and recovery, and one of the most important yet-to-be addressed potential bottlenecks, especially in OLTP workloads making frequent small changes to data. In this paper, we identify four logging-related impediments to database system scalability. Each issue challenges different level in the software architecture: (a) the high volume of small-sized I/O requests may saturate the disk, (b) transactions hold locks while waiting for the log flush, (c) extensive context switching overwhelms the OS scheduler with threads executing log I/Os, and (d) contention appears as transactions serialize accesses to in-memory log data structures. We demonstrate these problems and address them with techniques that, when combined, comprise a holistic, scalable approach to logging. Our solution achieves a 20%-69% speedup over a modern database system when running log-intensive workloads, such as the TPC-B and TATP benchmarks. Moreover, it achieves log insert throughput over 1.8GB/s for small log records on a single socket server, an order of magnitude higher than the traditional way of accessing the log using a single mutex.

Leveraging World Bank Resources for the Poorest: IDA Blended Financing Facility Proposal

With the Millennium Development Goals deadline only five years away, the international donor community faces significant challenges due to the global economic crisis, record government deficits, and simultaneous funding requests from nearly every multilateral development institution. This paper proposes a new World Bank financing model for creditworthy emerging economies, such as India and Vietnam, which currently receive billions of dollars in IDA assistance. In contrast to the current IDA-centric financing model, the IBRD would provide the same loan volumes to qualifying emerging economies while IDA would provide grant subsidies to buy down the concessionality level of these IBRD loans. As such, these countries would be held harmless both in terms of aid volumes and lending terms. By better leveraging the IBRD’s balance sheet for loan capital, IDA then could re-allocate what it otherwise would have provided to emerging economies. For the current IDA-15 replenishment period, this would mean up to $7.5 billion in additional assistance for the world’s poorest, most vulnerable countries. In relative terms, this would entail a 30 percent increase over existing levels. Of this, African countries would have received an additional $5.5 billion in IDA assistance. If donor governments find a way to scrape together increased contributions to IDA, then the allocation pie would grow by an even larger margin. The Inter-American Development Bank already successfully utilizes a similar approach for its lower middle-income and low-income country clients. It is time for World Bank shareholders to seriously consider the same resource-maximizing model. With the IDA-16 replenishment and IBRD general capital increase negotiations currently underway, they have an excellent window of opportunity to implement this win-win-win approach.

Analysis of Informal Credit Operations among Farmers In Atisbo Local Government Area of Oyo State, Nigeria

The study explored the operations, (savings and loan procurement), as well as the problems and prospects of the informal financial institutions in ATISBO Local Government Area of Oyo State, Southwest Nigeria. The sampling technique used was Stratified Random Sampling to select threevillages from the area and Systematic Random Sampling of respondents was conducted to select 120 respondents. With a mean age of 41.4 years, most of the respondents’ ages fell between 40 and 60 years. Some of the respondents (16.7%) had no formal education though they were managingfairly large household sizes, with a mean of 10 members/ household). 72.5% have no formal education, though the vast farming experience of the respondents; (mean 21.5 years) has been a facilitating factor in productivity improvement in the locality. Savings mobilized per year rangedfrom N 96,000 to N115, 000.00 with a mean saving of N 72,840.00. The results showed that the age, years of residency in the locality, education of the farmers, farm size and gender, all have significant relationships at 5 % with the volume of loan procured by the respondents. R2 value and adjusted R2 were 67% and 64%, F values were calculated as 13.2 respectively. The Linear function was selected as the equation of best fit. From the estimated linear lead equation, F-value was significant at 1% level of confidence, implying that the variables all have collective impact on the volume of savings mobilized from the informal sources by the respondents, hence the goodness of fit of the selected function. Some of the problems discovered on the operation of the informal services were short term expectation on loans repayment, inhibiting attitudes of group members, unsynchronized contributions to savings due to non-aligned cash flow in farming, elusive attitudes of money collectors and group coordinators and simultaneous requests by members for funds (loans), due to specific timing in farm operations and domestic requirements. The prospects of the informal financial services and groups in Nigeria could be improved if relevant policies are formulated and geared towards support for agricultural sectors and increase in the net farm income of farmers in such a way that the marginal propensity to save and invest more on farming could increase. The need to implement policies to ensure sustainable integration of the indigenous savings institutions into the operations of the Community Banks through the mobile rural banking strategies was suggested. Intensive use of extension services to facilitate adult literacy and learning among rural dwellers; especially farmers, to reduce illiteracy and empower farmers for savings, investment on agriculture as well as improved livelihood were also suggested.Key words: Informal Credit Operation, Savings, ATISBO L.G.A, farmers, Oyo State.

Impact of a simple load balancing approach and an incentive-based scheme on MANET performance

Most reactive mobile ad hoc network (MANET) routing protocols such as AODV and DSR do not perform search for new routes until the network topology changes. But, low node mobility does not affect the MANET connectivity and the same routes may be used for a long time. This may cause concentration of traffic on few mobile stations (MSs), which results in congestion and hence longer end-to-end delay. In addition, continuous use of MSs may cause their battery power to get exhausted rapidly. Expiration of MS energy causes disruption of connections traversing through the MSs and could generate many simultaneous new routing requests. Therefore, we propose a load balancing approach called Simple Load Balancing Approach (SLBA), which can be transparently added to any current reactive routing protocol such as AODV and DSR. SLBA minimizes the traffic concentration by allowing each MS to drop RREQ or to give up packet forwarding depending on its own traffic load. Meanwhile, MSs may deliberately give up forwarding packets to save their own energy. For encouraging MSs to volunteer in forwarding packets, we introduce a reward scheme for packet forwarding, named Protocol-Independent Fairness Algorithm (PIFA). We compare the performance of AODV and DSR with and without SLBA and PIFA. Simulation results indicate that SLBA can distribute traffic very well and improve the MANET performance. PIFA is also observed to prevent MANET partitioning and any performance degradation due to selfish nodes.

A fair assignment algorithm for multiple preference queries

Consider an internship assignment system, where at the end of each academic year, interested university students search and apply for available positions, based on their preferences (e.g., nature of the job, salary, office location, etc). In a variety of facility, task or position assignment contexts, users have personal preferences expressed by different weights on the attributes of the searched objects. Although individual preference queries can be evaluated by selecting the object in the database with the highest aggregate score, in the case of multiple simultaneous requests, a single object cannot be assigned to more than one users. The challenge is to compute a fair 1--1 matching between the queries and the objects. We model this as a stable-marriage problem and propose an efficient method for its processing. Our algorithm iteratively finds stable query-object pairs and removes them from the problem. At its core lies a novel skyline maintenance technique, which we prove to be I/O optimal. We conduct an extensive experimental evaluation using real and synthetic data, which demonstrates that our approach outperforms adaptations of previous methods by several orders of magnitude.

Improving OLTP scalability using speculative lock inheritance

Transaction processing workloads provide ample request level concurrency which highly parallel architectures can exploit. However, the resulting heavy utilization of core database services also causes resource contention within the database engine itself and limits scalability. Meanwhile, many database workloads consist of short transactions which access only a few database records each, often with stringent response time requirements. Performance of these short transactions is determined largely by the amount of overhead the database engine imposes for services such as logging, locking, and transaction management. This paper highlights the negative scalability impact of database locking, an effect which is especially severe for short transactions running on highly concurrent multicore hardware. We propose and evaluate Speculative Lock Inheritance, a technique where hot database locks pass directly from transaction to transaction, bypassing the lock manager bottleneck. We implement SLI in the Shore-MT storage manager and show that lock inheritance fundamentally improves scalability by decoupling the number of simultaneous requests for popular locks from the number of threads in the system, eliminating contention within the lock manager even as core counts continue to increase. We achieve this effect with only minor changes to the lock manager and without changes to consistency or other application-visible effects.

Scheduling shared scans of large data files

We study how best to schedule scans of large data files, in the presence of many simultaneous requests to a common set of files. The objective is to maximize the overall rate of processing these files, by sharing scans of the same file as aggressively as possible, without imposing undue wait time on individual jobs. This scheduling problem arises in batch data processing environments such as Map-Reduce systems, some of which handle tens of thousands of processing requests daily, over a shared set of files. As we demonstrate, conventional scheduling techniques such as shortest-job-first do not perform well in the presence of cross-job sharing opportunities. We derive a new family of scheduling policies specifically targeted to sharable workloads. Our scheduling policies revolve around the notion that, all else being equal, it is good to schedule nonsharable scans ahead of ones that can share IO work with future jobs, if the arrival rate of sharable future jobs is expected to be high. We evaluate our policies via simulation over varied synthetic and real workloads, and demonstrate significant performance gains compared with conventional scheduling approaches.

A practical SSL server performance improvement algorithm based on batch RSA decryption

The secure socket layer/ transport layer security(SSL/TLS) handshake protocol uses public key cryptographic algorithms such as RSA for key establishment. Typically, public key cryptographic algorithm is computational intensive due to the modular multiplications. Therefore, SSL/TLS servers often become swamped while performing public key decryptions when the simultaneous requests increase quickly. A batch RSA decryption algorithm was proposed. The novel algorithm provides the reasonable response time and optimizes server performance significantly. The decryption speedup is proportional to the batch size b, for instance, the speedup factor is 4, while in Shacham’s scheme the acceleration rate is only 2.5 when b = 4.

BioManager: the use of a bioinformatics web application as a teaching tool in undergraduate bioinformatics training

The completion of the human genome project, and other genome sequencing projects, has spearheaded the emergence of the field of bioinformatics. Using computer programs to analyse DNA and protein information has become an important area of life science research and development. While it is not necessary for most life science researchers to develop specialist bioinformatic skills (including software development), basic skills in the application of common bioinformatics software and the effective interpretation of results are increasingly required by all life science researchers. Training in bioinformatics is increasingly occurring within the university system as part of existing undergraduate science and specialist degrees. One difficulty in bioinformatics education is the sheer number of software programs required in order to provide a thorough grounding in the subject to the student. Teaching requires either a well-maintained internal server with all the required software, properly interfacing with student terminals, and with sufficient capacity to handle multiple simultaneous requests, or it requires the individual installation and maintenance of every piece of software on each computer. In both cases, there are difficult issues regarding site maintenance and accessibility. In this article, we discuss the use of BioManager, a web-based bioinformatics application integrating a variety of common bioinformatics tools, for teaching, including its role as the main bioinformatics training tool in some Australian and international universities. We discuss some of the issues with using a bioinformatics resource primarily created for research in an undergraduate teaching environment.

Practical algorithms for scheduling video data in a local area network environment

Simultaneous transmission of multiple high quality video streams from a server to the clients is becoming an increasingly important class of traffic in a network of workstations or cluster environment. With a powerful symmetric multiprocessor (SMP) as the server and a high-speed network, such transmission is practicable from a hardware point of view. However, the actual construction of such a video data server system entails tackling a number of difficult problems related to the provision of strict quality of service (QoS) guarantees. Among others, the smoothing and scheduling of multiple video packet streams are two crucial issues. Smoothing is concerned with reducing the rate variability of video streams in view of the fact that video data are usually compressed in a variable bit rate fashion. Scheduling is important to guarantee the requested QoS levels while maximizing the utilization of the resources. Although much work on smoothing has been done, it is not clear which scheduling scheme is suitable for multiplexing smoothed video data to the network. In this paper we present an extensive performance study of the EDF and RM scheduling algorithms which are modified to provide QoS guarantees for smoothed video data. With a probabilistic definition of QoS, admission control conditions are incorporated into the two algorithms. Furthermore, a counter-based scheduling module is included as the core scheduling mechanism which adaptively adjusts the actual QoS levels assigned to requests. Our theoretical analysis of the two modified algorithms, called QEDF and QRM, shows that the QRM algorithm is more robust than the QEDF algorithm for different workload and utilization conditions. We also propose to use a new metric called meta-QoS to quantify the overall performance of a packet scheduler given a set of simultaneous requests. In our experiments based on an SMP-based Linux platform, we find that the QRM algorithm can sustain a rather stable level of meta-QoS even when the workload and utilization levels are increased. On the other hand, the QEDF algorithm, due to its conservative admission control policy, is found to be not suitable for a high level of utilization and a large number of requests. In view of the lower complexity of the QRM algorithm, it seems that the QRM approach is a more suitable candidate for packet scheduling in the client-server environment considered in our study.

System-on-chip communication architecture: dynamic parallel fraction control bus design and test methodologies

Modern system-on-chip (SOC) designs consist of numerous heterogeneous components (embedded CPUs, dedicated hardware, FPGAs, embedded memories and so on) integrated onto a single chip. The on-chip communication is becoming the bottleneck for these SOC designs, and efficient contention resolution schemes for managing simultaneous access requests to the communication resources are required to prevent system performance degradation. A new SOC on-chip communication architecture, Dynamic Parallel Fraction Control Bus, which offers an attractive solution for the problem and addresses shortcomings of existing communication architectures is presented. To demonstrate the benefits of the proposed architecture, several existing communication architectures were compared with the proposed architecture on the basis of two application prototypes. Through experimentation it has been shown that the proposed architecture not only exhibits both hardware simplicity and system performance improvements, but also produces better bus bandwidth control and scalability properties compared with the existing communication architectures.

It Takes More Than a Practice Visit: Effective General Practice Engagement

General practice engagement (GPE) is an important function, communicating new knowledge, new treatments and new ways of working with GPs and practice staff. It is necessary for health system decision-makers to recognise that GPE takes more than a practice visit. In this case study, the Dandenong District Division of General Practice found that, to be effective, GPE must be practice-appropriate (planned) and targeted within a whole-of-practice approach. Practice visits need to be supported by other complementary strategies and delivered by a trusted representative from institutions that appreciate the business of general practice and the culture in which it operates. Strategies require coordination so that general practice is not overwhelmed by simultaneous requests for change

An Experiment on Strategic Capacity Reduction

A firm may strategically decrease capacity to gain bargaining power over its suppliers. While traditional models of bargaining imply that the incentive to do so is minimal, I report results from a laboratory experiment that suggest the existence of incentives to decrease capacity quite substantially below efficient levels, excluding at least 30% of available suppliers. The experiment is a market game in which subjects—both MBA students and executives of two large corporations—make simultaneous requests for their share of the profit if they are included among a firm’s suppliers. The lowest offers are selected with remaining subjects earning zero. Treatments vary the capacity constraint representing the number of suppliers that can be accommodated. As capacity decreases, so does the average request, but according to a pattern quite divorced from equilibrium predictions. The pattern of these requests suggests an incentive to commit to a capacity which excludes at least 30% of suppliers.

Application of soft computing techniques to adaptive user buffer overflow control on the Internet

Two novel expert dynamic buffer tuners/controllers, namely, the neural network controller (NNC) and the fuzzy logic controller (FLC) are proposed in this paper. They use soft computing techniques to eliminate buffer overflow at the user/server level. As a result they help shorten the end-to-end service roundtrip time (RTT) of the logical Internet transmission control protocol (TCP) channels. The tuners achieve their goal by maintaining the given safety margin Delta around the reference point of the {0,Delta}2 objective function. Overflow prevention at the Internet system level, which includes the logical channels and their underlying activities, cannot shorten the service RTT alone. In reality, unpredictable incoming request rates and/or traffic patterns could still cause user-level overflow. The client/server interaction over a logical channel is usually an asymmetric rendezvous, with one server serving many clients. A sudden influx of simultaneous requests from these clients easily inundates the server's buffer, causing overflow. If this occurs only after the system has employed expensive throttling and overflow management resources, the delayed overflow rectification could lead to serious consequences. Therefore, it makes sense to deploy an independent user-level overflow control mechanism to complement the preventative effort by the system. Together they form a unified solution to effectively stifle channel buffer overflow

B3A: Prompting Cooperation Among Rational Participants in P2P Bulk File Sharing Environments

Peer-to-peer (P2P) file sharing systems assume that their users download files in proportion to their sharing. Unfortunately, users are unlikely to do so without an incentive mechanism. Previous solutions to the problem required some types of centralized control, which strays from the spirit of P2P to provide long-term incentives. This paper presents the balance-based bandwidth allocation, B 3 A, an incentive framework to inspire participants to share files. In the B 3 A framework, each peer keeps the differences between the amount of data it has received from each peer and the amount it has sent to that one. When receiving simultaneous requests from various peers, the peer prefers to allocate its limited upload bandwidth to those peers with larger differences. Therefore, the downloading bandwidth perceived by a peer is positively related to its contributions to others, consequently stimulating it to share more files. The B 3 A framework is fully decentralized, scalable, and secure.