面向微处理器猜测执行过程中预载入数据的Cache污染控制方法

“存储墙”问题已经成为处理器性能提升的主要障碍,而处理器内核猜测执行预测路径上访存指令时预载入的存储器数据所导致Cache污染会严重影响处理器性能.本文提出一种针对猜测执行过程中预载入数据的Cache污染控制方法CSDA.首先,利用置信度评估技术从所有预测路径中分离出错误概率较大的路径.然后,根据低置信度污染型访存指令识别历史表将低置信度预测路径上的访存指令划分为预取型和污染型,为污染型的访存指令建立低优先级Load/Store队列,并采用污染数据Cache存储污染数据.仿真结果表明,在双核模式下,CSDA策略相对于baseline结构来说,L1 D-Cache缺失率降低幅度从9％-23％,平均降低了17％;L2 Cache缺失率的下降范围从1.02％-14.39％,平均为5.67％;IPC的提升幅度从0.19％ -5.59％,平均为2.21％.     

Versioning XML-based office documents

The ability to reliably merge independent updates of a document is a crucial prerequisite to efficient collaboration in office work. However, merge support for common office document standards like OpenDocument or OfficeOpenXML is still in its infancy. In this paper, we present a consistent versioning model for XML documents in general including merge support. This is achieved by using context-aware fingerprints that identify edit operations and allow for a conflict detection. We show how to extract tracked changes from office documents and map them on our delta model. Experimental results indicate that our fingerprinting technique is efficient and reliable.     

WS-BPEL Extensions for Versioning

This article proposes specific extensions for WS-BPEL (Business Process Execution Language) to support versioning of processes and partner links. It introduces new activities and extends existing activities, including partner links, invoke, receive, import, and onmessage activities. It proposes version-related extensions to variables and introduces version handlers. The proposed extensions represent a complete solution for process-level and scope-level versioning at development, deployment, and run-time. It also provides means to version applications that consist of several BPEL processes, and to put temporal constraints on versions. The proposed approach has been tested in real-world environment. It solves major challenges in BPEL versioning.     

Versioning Support in the HyperProp System

This paper discusses version control for hypermedia models with composite nodes that allow distinct representations of the same information segment to be treated as versions. Several problems arise from the possibility of a node being contained in different nested compositions, as well as being presented (edited) with different representations. The paper discusses these issues, relating partial solutions proposed in several hypermedia models and presenting the proposal defined in the Nested Context Model of the HyperProp system.     

Speculative multithreaded processors

Speculation will overcome the limitations in dividing a single program into multiple threads that can execute on the multiple logical processing elements needed to enhance performance through parallelization     

用对象标识与版本管理机制改进关系数据库设计

分析了关系数据库在引用一致性，历史数据库管理上存在的缺陷，提出了使用对象标识与版本管理机制改进关系数据库设计的思想，并给出了具体的设计步骤，方法，标准例程。     

Selective Versioning for Transaction Management in Data Warehousing

To speed up online analytical processing, data warehousing systems materialize views derived from several operational databases. When the operational databases happen to change, the materialized views get stale. To enhance the freshness of the materialized views, this article proposes a new concurrency control scheme that makes use of selective versioning to aid analytical transactions in continuously accessing fresh data.     

本体演化及本体的版本管理机制研究

本体版本管理机制是本体管理中的一个子问题,本体随着变化不断演化,有效的维护和管理这些变化,以及维护同一本体的不同版本之间的关联是非常重要的。本文首先介绍了本体版本管理机制的背景知识和相关定义,分析了本体变化的原因及其变化的结果,提出了一个本体版本管理机制的管理框架并进行了具体阐述。     

一种基于两级缓存的协同缓存机制

信息中心网络(information-centric networking,简称ICN)将网络通信模式从当前的以地址为中心转变为以信息为中心.泛在化缓存是ICN重要特性之一,它通过赋予网络任意节点缓存的能力来缓和服务器的压力,降低用户访问延迟.然而,由于缺少内容热度的分布感知,现有ICN缓存策略仍存在缓存利用率较低、缓...     

机群代理的单一缓存映像技术

为了在Web机群代理中有效定位缓存对象在节点机中的位置，必须实现单一缓存映像，以隐藏机群的分布和异构特性，为客户提供一致的缓存资源。为解决该问题，文中首先提出一个缓存摘要管理器体系结构，该结构基于各个缓存节点机的摘要、结合负载平衡信息，可有效定位缓存节点机，然后给出了机群代理中缓存节点机与缓存摘要管理器的实现方法。     

Versioning and configuration management in an object-oriented data model

Many database applications require the storage and manipulation of different versions of data objects. To satisfy the diverse needs of these applications, current database systems support versioning at a very low level. This article demonstrates that application-independent versioning can be supported at a significantly higher level. In particular, we extend the EXTRA data model and EXCESS query language so that configurations can be specified conceptually and non-procedurally. We also show how version sets can be viewed multidimensionally, thereby allowing configurations to be expressed at a higher level of abstraction. The resulting model integrates and generalizes ideas, in CAD systems, CASE systems, and temporal databases.     

Speculative incoherent cache protocols

Multiprocessing and multithreading are becoming ubiquitous even on single chips. With increasing cache sizes, coherence misses in such systems will account for a larger fraction of all cache misses. As communication latencies increase, this larger fraction of coherence misses will cause significant and increased performance losses. Tuning coherence protocols for specific communication patterns and applications can reduce communication latencies. However, these optimizations increase a protocol's design complexity, making the protocol difficult to verify. A competing approach requires parallel programmers to tune applications to work well with simpler protocols. Speculative execution has successfully improved performance in various scenarios. We propose a new type of load speculation, called coherence decoupling. Coherence decoupling is a microarchitectural mechanism that implements separate protocols for speculative use and for the eventual verification of values. The technique reduces the effect of long communication latencies while mitigating the burdens on the coherence protocol designer and the parallel programmer     

Speculative optimizations for interpreting environments

Most constrained systems use interpreters to run mobile programs written in Java. Such interpreters are designed to minimize resource usage and often do not allow mobile code in the devices to be changed. For this reason, runtime optimization is typically not supported, even though it is completely feasible. In this paper, we propose optimistic optimization as a concept for improving application performance in restricted interpreter environments. In an optimistic optimization, a mobile program is restructured speculatively during code generation. This requires that it is possible to undo such optimizations, at runtime, if an incorrect use is detected or the set of available classes has changed when compared with compile time. Experimental results show that interpreted applications using optimistic optimizations tend to run faster when compared with their conventionally optimized counterparts. Compared with standard load elimination, reductions in runtimes of up to 9% for optimistic load elimination and up to 23% for the combined optimization were achieved. Whereas an average performance improvement of 1.87% for optimistic load elimination and 3.7% for the combined optimization could be realized. Copyright © 2013 John Wiley & Sons, Ltd.     

Speculative Memory Cloaking and Bypassing

We revisit memory hierarchy design viewing memory as an inter-operation communication mechanism. We show how dynamically collected information about inter-operation memory communication can be used to improve memory latency. We propose two techniques: (1) Speculative Memory Cloaking, and (2) Speculative Memory Bypassing. In the first technique, we use memory dependence prediction to speculatively identify dependent loads and stores early in the pipeline. These instructions may then communicate prior to address calculation and disambiguation via a fast communication mechanism. In the second technique, we use memory dependence prediction to speculatively transform DEF-store-load-USE dependence chains within the instruction window into DEF-USE ones. As a result, dependent stores and loads are taken off the communication path resulting in further reduction in communication latency. Experimental analysis shows that our methods, on the average, correctly handle 40% (integer) and 19% (floating point) of all memory loads. Moreover, our techniques result in performance improvements of 4.28% (integer) and 3.20% (floating point) over a highly aggressive, dynamically scheduled processor implementing naive memory dependence speculation. We also study the value and address locality characteristics of the values our methods correctly handle. We demonstrate that our methods are orthogonal to both address and value prediction.     

Cache Profiling技术

如何减少和隐藏cache失效的延迟,是人们关注的热点。编译器为了得到cache访问命中的情况,往往使用模拟器去跑一遍来得到结果,这样的速度很慢。为了克服以上缺点,提出了在编译器中作cache profiling来获取cache访问的信息。类似于value profiling和stride profiling,cache profiling对访存指令作插装,可以有效地提高速度,并且只需要编译器的支持即可。Cache profiling获得的信息可以用来改进指令调度、软件预取、生成cache hint和辅助线程等。     

基于缓存框架的Web缓存研究

该文重点研究了缓存框架OSCache的缓存组件与Hibernate的数据缓存管理。提出OSCache、Ehcache和Hibernate整合在一起的Web缓存方案。     

基于缓存框架的Web缓存研究

该文重点研究了缓存框架OSCache的缓存组件与Hibernate的数据缓存管理。提出OSCache、Ehcache和Hibernate整合在一起的Web缓存方案。     

基于本体指标的本体版本演变分析方法

随着语义Web的发展和Web本体语言(Web ontology language,OWL)的普及,在各个领域出现了越来越多大规模的本体,其中部分本体已历经多个版本的演变,因而需要一种简单而有效的方法,帮助人们分析和了解不同版本的本体内部的变化情况。在已有的本体指标相关工作的基础上,提出了Property层上的4个本体指标,并且选择版本更新比较完整的Open GALEN和Open Cyc本体作为数据集,基于OWL-API设计了一个实用工具,对多个版本下的本体在Ontology层、Class层和Property层的指标进行了度量。通过分析实验结果和指标所代表的意义,总结出本体指标变化所体现出的本体版本演变的规律。