30590203
Efficient State-Saving Architectures for Power-Mode Switching
Time and energy is expended in switching between power modes (e.g., active, hibernate, sleep, etc.). Powering off cache is one major reason for this. When there is a switch in the power-mode involving cache power-off, the system spends time and energy in filling the cache with new data (inherent cache misses). In our technique, before powering off the cache, we save its state in Embedded DRAM and bring it back when the previous power mode is restored. Our experiments have showed that in a majority of cases the cache contents are too valuable to be erased. By saving the contents we can reduce switching speed and energy. We present a heuristic to save the most relevant cache contents so that power and delay overheads are minimized. To measure the area overhead a synthesizable VHDL model was designed.
40618061
Transaction Recovery in Distributed DB/DC Systems: A Progressive Approach
26676459
Progressive Transaction Recovery in Distributed DB/DC Systems
The demand for on-line transaction processing has grown rapidly in recent years. To meet the transaction demand, several DB (database management) and DC (data communication management) subsystems can be coupled together to form a distributed DB/DC system. A key problem is to provide these distributed systems with effective means to recover transactions upon failure while paying little performance penalty during normal processing. Also, there should be minimal interference of fault-free components, during the recovery of failed component. By decentralizing recovery management, and using transaction level structural information to eliminate costly lower level handshaking protocols, proposed progressive transaction recovery protocols seek to solve the problem. A queueing model for evaluating the transaction response time during normal processing for the progressive and pessimistic protocols is developed and solved, via simulation. The progressive recovery protocols are shown to reduce normal processing overhead and lead to performance improvement over the pessimistic protocol.
8777661
Adaptive transaction routing in a heterogeneous database environment
The issue of transaction routing in a heterogeneous database environment is examined where transaction characteristics like reference locality implies that certain processing systems can be identified as being, in general, more suitable than others for a given transaction class. Routing which ignores these distinctions in an attempt to balance system load can degrade system performance. An adaptive routing strategy is considered which: (1) estimates the response time based on a steady-state analysis; (2) monitors how well actual response time conforms to the estimate; and (3) adaptively adjusts future estimates through a feedback control based on (2). It is found that the adaptive strategy greatly enhances performance robustness as compared to the results of the strategy without feedback. The feedback process used alleviates the sensitivity to accurate estimations of workload and system parameters. Various simulation studies are used to illustrate the adaptive strategy's robustness.<<ETX>>
31591898
Scanning the issue - special issue on real-time systems
10753893
Evaluation of Error Recovery Blocks Used for Cooperating Processes
Three alternatives for implementing recovery blocks (RB's) are conceivable for backward error recovery in concurrent processing. These are the asynchronous, synchronous, and the pseudorecovery point implementations. Asynchronous RB's are based on the concept of maximum autonomy in each of concurrent processes. Consequently, establishment of RB's in a process is made independently of others and unbounded rollback propagations become a serious problem. In order to completely avoid unbounded rollback propagations, it is necessary to synchronize the establishment of recovery blocks in all cooperating processes. Process autonomy is sacrificed and processes are forced to wait for commitments from others to establish a recovery line, leading to inefficiency in time utilization. As a compromise between asynchronous and synchronous RB's we propose to insert pseudorecovery points (PRP's) so that unbounded rollback propagations may be avoided while maintaining process autonomy. We developed probabilistic models for analyzing these three methods under standard assumptions in computer performance analysis, i.e., exponential distributions for related random variables. With these models we have estimated 1) the interval between two successive recovery lines for asynchronous RB's, 2) mean loss in computation power for the synchronized method, and 3) additional overhead and rollback distance in case PRP's are used.
16022713
Query based event extraction along a timeline
In this paper, we present a framework and a system that extracts events relevant to a query from a collection C of documents, and places such events along a timeline. Each event is represented by a sentence extracted from C, based on the assumption that "important" events are widely cited in many documents for a period of time within which these events are of interest. In our experiments, we used queries that are event types ("earthquake") and person names (e.g. "George Bush"). Evaluation was performed using G8 leader names as queries: comparison made by human evaluators between manually and system generated timelines showed that although manually generated timelines are on average more preferable, system generated timelines are sometimes judged to be better than manually constructed ones.
850911
Usability-based caching of query results in OLAP systems
In this paper we propose a new cache management scheme for online analytical processing (OLAP) systems based on the usability of query results in rewriting and processing other queries. For effective admission and replacement of OLAP query results, we consider the benefit of query results not only for recently issued queries but for the expected future queries of a current query. We exploit semantic relationships between successive queries in an OLAP session, which are derived from the interactive and navigational nature of OLAP query workloads, in order to classify and predict subsequent future queries. We present a method for estimating the usability of query results for the representative future queries using a probability model for them. Experimental evaluation shows that our caching scheme using the past and future usability of query results can reduce the cost of processing OLAP query workloads effectively only with a small cache size and outperforms the previous caching strategies for OLAP systems.
37385528
A framework for handling dependencies among web services transactions
This paper proposes an effective Web services (WS) transaction management framework to automatically manage inconsistencies occurred by relaxing isolation of WS transactions.
14282973
Closing the Gap: Learning-Based Information Extraction Rivaling Knowledge-Engineering Methods
In this paper, we present a learning approach to the scenario template task of information extraction, where information filling one template could come from multiple sentences. When tested on the MUC-4 task, our learning approach achieves accuracy competitive to the best of the MUC-4 systems, which were all built with manually engineered rules. Our analysis reveals that our use of full parsing and state-of-the-art learning algorithms have contributed to the good performance. To our knowledge, this is the first research to have demonstrated that a learning approach to the full-scale information extraction task could achieve performance rivaling that of the knowledge engineering approach.
7927244
GM-WTA: An efficient workflow task allocation method in a distributed execution environment
A workflow is a collection of units of work called workflow tasks which cooperatively realize a business objective by utilizing system resources such as databases. The roles of workflow tasks are performed in the order driven by a computer representation of the workflow logic. During completing each task's role, the remote control transfers and the remote resource accesses may often occur in a distributed workflow system. Hence, the efficient distribution of workflow components, especially workflow tasks, is so effective as to improve the performance of workflow processing. If we can place adjacent workflow tasks as close as possible and locate workflow tasks near to the required resources, we can significantly reduce the overhead of workflow processing.In this paper, we propose an efficient workflow task allocation method in a distributed workflow system, which is based on the locality principle. The method that utilizes the concept of graph partitioning can improve the performanace of workflow processing by minimizing the remote processing costs incurred during workflow execution. In addition, we perform several experiments to evaluate our proposed method.