• Journal of KIISE:Computer Systems and Theory
• /
• v.27 no.2
• /
• pp.177-187
• /
• 2000

In the past several years, many systems which adopted ring topology with high-speed unidirectional point-to-point links have emerged to overcome the limit of bus for interconnection network of clustered multiprocessor system. However, rapid increase of processor speed and performance improvement of local bus and memory system limit scalability of system with point-to-point link of standard bandwidth. Therefore, necessity to extend bandwidth is emphasized. In this paper, we adopt PANDA system as base model, which is clustering-based multiprocessor system. By simulating a model adopting commercial processor and local bus specification, we show that point-to-point link is bottleneck of system performance, and bandwidth expansion by more than 200% is needed. To expand bandwidth of interconnection network, it needs excessive design cost and time to develop new point-to-point link with doubled bandwidth. As an alternative to double bandwidth, we propose several ways to implement dual ring -simple dual ring, transaction-separated dual ring, direction-separated dual ring- by using off-the-shelf point-to-point links with IEEE standard bandwidth. We analyze pros. and cons. of each model compared with doubled-bandwidth single ring by simulation.

• The KIPS Transactions:PartA
• /
• v.12A no.3 s.93
• /
• pp.253-262
• /
• 2005

Local accounting system used by UNIX-like operating system provides the accounting information of processes that are in single host. But it is impossible for this local accounting system to record the total resource consumption data of all processes for doing the same job simultaneously. In this paper, we implement accounting system to measure and manage resource usage for MPI(Message Passing Interface) job in the clustering environment. We designed and implemented the accounting system which measure resource usage of each process runs on a cluster node and record the interconnection information of the entire set of processes across network. Also we implemented accounting system which collect the resource usage data of process in the local accounting system and generate the job-level accounting information. Finally, to evaluate the resource consumption data measured by this accounting system we compare with the data collected by local scheduler that widely used in large scale clustering environment.

• Journal of IKEEE
• /
• v.1 no.1 s.1
• /
• pp.31-46
• /
• 1997

In this paper, a parallel Optimal Best-First search Branch-and-Bound(B&B) algorithm(pobs) is designed and evaluated for MIN-based multiprocessor systems. The proposed algorithm decomposes a problem into G subproblems, where each subproblem is processed on a group of P processors. Each processor group uses tile sub-Global Best-First search technique to find a local solution. The local solutions are broadcasted through the network to compute the global solution. This broadcast provides not only the comparison of G local solutions but also the load balancing among the processor groups. A performance analysis is then conducted to estimate the speed-up of the proposed parallel B&B algorithm. The analytical model is developed based on the probabilistic properties of the B&B algorithm. It considers both the computation time and communication overheads to evaluate the realistic performance of the algorithm under the parallel processing environment. In order to validate the proposed evaluation model, the simulation of the parallel B&B algorithm on a MIN-based system is carried out at the same time. The results from both analysis and simulation match closely. It is also shown that the proposed Optimal Best-First search B&B algorithm performs better than other reported schemes with its various advantageous features such as: less subproblem evaluations, prefer load balancing, and limited scope of remote communication.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.12
• /
• pp.1345-1352
• /
• 2014

Bus architecture of SoC has been replaced by NoC in recent years. Noc uses the multi-clock domains to transmit and receive data between neighbor network interfaces and they have same frequency, but a phase difference because of clock skew. So a synchronizer is used for a mesochronous frequency in interconnection between network interfaces. In this paper the metastability is defined and analyzed in a D latch and a D flip-flop to search the possibilities that data can be lost in the process of sending and receiving data between interconnects when a local frequency and a transmitted frequency have a phase difference. 180nm CMOS model parameter and 1GHz are used to simulate them in HSpice. The simulation results show that the metastability happens in a latch and a flip-flop when input data change near the clock edges and there are intermediate states for a longer time as input data change closer at the clock edge. And the next stage can lose input data depending on environmental conditions such as temperature, processing variations, power supply, etc. The simulation results are very useful to design a mescochronous synchronizer for NoC.

• Journal of KIISE:Computing Practices and Letters
• /
• v.5 no.5
• /
• pp.639-650
• /
• 1999

Generally, a performance management consists of the iterative process of performance monitoring, performance analysis, and performance tuning. In this paper, we describe the design and implementation of performance monitor and performance tuner which can be used on the top of SPAX, also known as TICOM IV. SPAX has a hierarchical structure. All nodes, each of which has a local memory, are connected to the interconnection network and constructed to form clusters. Therefore, it is necessary to develop a new performance monitor reflecting the underlying hierarchical structure of SPAX, to implement performance monitoring more effectively. Implemented performance monitor can monitor the state of nodes, clusters, and total system of SPAX at realtime. And, implemented performance tuner can change the value of variables related to the performance of SPAX. System manager can perform an effective performance management by using the proposed performance management tools.

• The KIPS Transactions:PartC
• /
• v.18C no.6
• /
• pp.423-432
• /
• 2011

Recently, OpenFlow has been paid attention to as a fundamental technology which provides a function of virtualization and programmability in network. In Korea, deployment of OpenFlow networks in campuses and the interconnection between them through tunneling in layer 3 has been performed. However, the performance of the interconnected networks is decreased due to delay in IP layer. In this paper, we design and deploy nation-wide, not local, OpenFlow networks in a pure layer 2 environment over KREONET. After that, we do end-to-end Round-trip Time measurements and TCP/UDP performance tests in OpenFlow and normal networks, and do comparison and analysis on the test results. The results show that the nation-wide OpenFlow networks provide equal performance to normal networks except for the initial packet loss for UDP streaming. In regards to the performance decrease due to early UDP packet loss, we can mitigate it by implementing exceptional procedures in a controller which deal with the same continuous "Packet_in" events.

• KIISE Transactions on Computing Practices
• /
• v.23 no.9
• /
• pp.517-534
• /
• 2017

This paper proposes an Internet of Things (IoT) middleware called Middleware for Cooperative Interaction of Things (MinT). MinT supports a fully distributed IoT environment in which IoT devices directly connect to peripheral devices, easily constructing a local or global network and sharing their data in an energy efficient manner. MinT provides a sensor abstract layer, a system layer and an interaction layer. These layers enable integrated sensing device operations, efficient resource management, and interconnection between peripheral IoT devices. In addition, MinT provides a high-level API, allowing easy development of IoT devices by developers. We aim to enhance the energy efficiency and performance of IoT devices through the performance improvements offered by MinT resource management and request processing. The experimental results show that the average request rate increased by 25% compared to existing middlewares, average response times decreased by 90% when resource management was used, and power consumption decreased by up to 68%. Finally, the proposed platform can reduce the latency and power consumption of IoT devices.