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在透明计算中,服务端存储并管理着所有用户所需的操作系统、应用软件和个性化数据,并高效处理来自透明网络的用户资源请求服务。因此,服务端是透明计算系统性能的瓶颈。为制定更高效的缓存策略提供有效的依据,基于信息熵和三次指数平滑对透明计算用户行为特征进行分析和预测。首先基于信息熵策略分析用户访问行为特征,进而利用指数平滑预测算法预测将来一段时间内数据块的访问频率,在真实数据的实验结果上验证了预测方法的有效性。 相似文献
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本文针对增益透明半导体光放大器(GT-SOA)的偏振旋转效应进行了研究,并将其利用于光纤环型全光缓存器中作为偏振旋转光开关,作为全光缓存器的关键器件。本文根据增益透明半导体光放大器(GT-SOA)的偏振旋转效应理论模型编制仿真软件。建立了基于GT-SOA偏振旋转效应的全光缓存器仿真系统,将GT-SOA的仿真模块嵌入系统仿真软件中进行仿真,并对其单波长缓存系统中信号速率、传输码型、缓存时间等对系统性能的影响进行了仿真和分析。仿真分析结果表明,在该缓存系统中GT-SOA可以很好的完成光开关的作用。 相似文献
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在E级计算时代,超算系统一般使用多层存储架构以满足应用数据访问的容量和性能需求,这种架构中不同层次的存储介质差异较大,难以实现统一名字空间管理,往往需要应用修改数据访问流程才能最大程度利用到多层存储的性能和容量优势。针对多层存储统一名字空间的问题,提出针对非易失性双列存储模块(NVDIMM)的块级缓存和针对突发缓冲存储(BB)的文件级缓存技术。基于NVDIMM的块级缓存技术对缓存窗口灵活控制,以支持数据块粒度的异步读写,实现NVDIMM与BB层统一名字空间管理;基于BB的文件级缓存技术将数据缓存在BB层中,并动态迁移和管理文件副本,实现BB层与传统磁盘文件系统统一名字空间管理。在神威E级原型验证系统中的测试结果表明,所提出的两种技术较好地解决了多层存储的透明加速难题,NVDIMM块级缓存与BB相比,在缓存窗口16 MB时128 KB顺序读写带宽分别提升27%和36%,8 KB随机读写带宽分别提升20%和37%;基于BB的文件缓存技术利用BB的高带宽支撑数据访问,与全局文件系统相比,128 KB顺序读写带宽分别提升55%和141%,8 KB随机读写带宽分别提升163%和209%。此外,实际应用的测试也表明以上两种缓存技术具有透明的存储加速效果。 相似文献
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为了降低信息中心网络(Information Centric Networking, ICN)缓存冗余度和平均接入代价,提出一种基于节点中心性度量近似算法的协作缓存策略Centrality Metric Approximation Algorithm (CMAA)。考虑到精确计算最短路径的工作量对缓存性能的影响,CMAA策略利用最短路径近似估计值以提高节点中心性的计算效率,将节点中心性近似度量加权融合值、节点热度和缓存利用率三者作为缓存影响因子,计算得出兴趣包转发路径各节点的缓存优先级。在多种实验条件下对CMAA进行仿真实验,结果表明与LCE (Leave Copy Everywhere)和CLFM (Cache “Less for More”)相比,CMAA在平均缓存请求时延变化不大的情况下,可有效地提高缓存命中率,降低平均接入代价,从而改善缓存系统性能。 相似文献
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为了解决代码测试系统测试C项目的时间开销较大这一问题,本文提出了一种基于缓存估算模型的性能优化方法。该方法向代码测试系统中引入了缓存技术,并且建立了缓存规模估算模型。不相似的C项目应用该模型计算出的缓存规模是不一样的。使用缓存规模估算模型后,代码测试系统文件缓存的规模能够随着C项目的改变而发生改变,具有动态变化的能力。缓存估算模型已在系统中实现,对4个开源C项目的测试结果表明:该优化方法能有效地提高代码测试系统测试C项目时的时间性能。 相似文献
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随着大数据时代数据规模的激增,内存计算框架得到了长足发展。主流内存计算框架Apache Spark使用内存来缓存中间结果,大幅度地提升了数据处理速度。同时,具有较快的读写速度和较大容量的非易失性存储器NVM在内存计算领域展现出了巨大的发展前景,使用DRAM和NVM构建Spark混合缓存系统成为一种可行方案。文中提出了一种基于DRAM-NVM混合内存的Spark缓存系统,该系统选择平面混合缓存模型作为设计方案,然后为缓存块管理系统设计了专用的数据结构,并提出了适用于Spark的混合缓存系统整体设计架构。另外,为了将频繁访问的缓存块保存在DRAM缓存中,提出了基于缓存块最小重用代价的混合缓存管理策略。首先从DAG信息中获取RDD的未来重用次数,未来重用次数多的缓存块将被优先保存在DRAM缓存中,并在缓存块迁移时考虑了迁移成本。设计实验表明,DRAM-NVM混合缓存相比原有缓存系统的性能平均提升了53.06%,对于相同的混合内存,所提策略相比默认缓存策略有平均35.09%的提升。同时,使用文中设计的混合系统只需要1/4的DRAM和3/4的NVM作为缓存,就能达到全部DRAM缓存约79%的性能... 相似文献
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随着计算规模越来越大,网络存储系统应用领域越来越广泛,对网络存储系统I/O性能要求也越来越高.在存储系统高负载的情况下,采用低速介质在客户机和网络存储系统的I/O路径上作为数据缓存也变得具有实际的意义.设计并实现了一种基于磁盘介质的存储系统块一级的缓存原型D-Cache.采用两级结构对磁盘缓存进行管理,并提出了相应的基于块一级的两级缓存管理算法.该管理算法有效地解决了因磁盘介质响应速度慢而带来的磁盘缓存管理难题,并通过位图的使用消除了磁盘缓存写Miss时的Copy on Write开销.原型系统的测试结果表明,在存储服务器高负载的情况下,缓存系统能够有效地提高系统的整体性能. 相似文献
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设计并实现了一个基于透明计算模式的I/O Server系统,I/O Server和I/O Client是一个在透明计算环境下,支持多操作系统远程启动和运行的网络存储访问服务I/O Manager的2个软件模块,I/O Server工作在服务器端,I/O Client工作在客户端。在透明计算模式中,各客户机硬件与操作系统分离,用户需要的操作系统的应用程序存储在服务器端。在客户机启动时,I/O Server和启动协议将I/O Client下载到端系统上运行,然后I/O Client向I/O Server发出I/O请求,I/O Server对收到的I/O请求加以分析,进行优先级分类,在优先级分时轮转调度I/O请求、操作服务器上的虚拟硬盘文件,并通过预取和缓存策略减少磁盘I/O操作,将处理结果返回给客户端,支持操作系统的远程启动,并为系统运行时的各种请求提供服务。 相似文献
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Location Dependent Information Services (LDISs), through which mobile clients can access location sensitive data such as weather
information, traffic reports, and local news, are gaining increasing popularity in recent years. Due to limited client power
and intermittent connectivity, caching is an important approach to improve the performance of LDISs. In this paper, we propose
a cache replacement policy called Location Dependent Cooperative Caching (LDCC). Unlike existing location dependent cache
replacement policies, the LDCC strategy applies a prediction model to approximate client movement behavior and a probabilistic
transition model to analyze the communication cost. These models are used in the design of a cache replacement policy to improve
system overall performance. Simulation results demonstrate that the proposed strategy significantly outperforms existing caching
policies in providing LDIS in mobile ad hoc networks. 相似文献
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分布式文件系统需要有一种机制对来自各个客户端的并发访问进行控制,维护文件数据的一致性。锁是实现并发控制最流行的机制。研究了Lustre文件系统的分布式I/O范围锁的模型,并对它的各种应用进行了优化。介绍了Lustre分布式锁的基本概念,对基于锁实现数据客户端写回缓冲以及多写者文件大小的动态获取的算法进行了分析;提出自适应I/O锁策略,基于区间树的范围锁冲突检测优化策略以及客户端锁淘汰策略来增强Lustre锁服务的性能和扩展性。 相似文献
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Data caching is used to improve the response time and the power consumption of a mobile client in a mobile computing environment. To enhance the performance of data caching, one needs to improve the hit ratio and to reduce the cost in processing a cache miss. In a mobile computing environment, a cached data item of a mobile client needs to remain up-to-date with respect to its corresponding data item in the server. A cached data item which is out of date is called a cached invalidated data item. Accessing a cached invalidated data item can be regarded as processing a cache miss. To access a cached invalidated data item, a mobile client needs to download the new content of the data item from the broadcast channel. This operation is called a re-access operation in this paper. Re-accessing a cached invalidated data item incurs large tuning time overhead. In this paper, we propose a re-access scheme that reduces this overhead by allowing a mobile client to access a cached invalidated data item from the broadcast channel without accessing indices. We analyze the performance of the proposed scheme and validate the analysis through experiments. The experiments showed that the proposed scheme significantly reduces the tuning time of a mobile client. Furthermore, the proposed scheme is robust in the sense that it allows changes on the broadcast structure in data broadcasting. 相似文献
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Po‐Cheng Chen Jyh‐Biau Chang Yen‐Liang Su Ce‐Kuen Shieh 《Concurrency and Computation》2010,22(18):2488-2513
Conventional remote data access middlewares usually provide client applications with either a pre‐staging scheme or an on‐demand access scheme to fetch data. The pre‐staging scheme uses parallel downloads to fetch a completed input file from multiple data sources, even when only a tiny file fragment is required. Such a transfer scheme consumes unnecessary data transmission time and storage space. In contrast, the on‐demand scheme downloads only the required data blocks from a single data source and does not fully utilize the downstream bandwidth of the computing nodes. This paper presents a middleware called ‘Spigot’ that facilitates legacy (grid‐unaware) applications to transparently access remote data by using native I/O function calls. Spigot uses the on‐demand concept to avoid unnecessary data transfer and adopts a co‐allocation download algorithm to improve the data transfer performance. Moreover, it uses the pre‐fetching strategy to reduce the data waiting time by overlapping data acquisition and data processing. It also provides the client application with its own user‐level cache, which is advantageous since a larger cache space is available in comparison with the kernel‐level cache. Further, it is easy to maintain data consistency between Spigot nodes. The experimental results indicate that Spigot achieves superior performance in reducing the data waiting time than the pre‐staging and the on‐demand access schemes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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A cache invalidation scheme for continuous partial match queries in mobile computing environments 总被引:1,自引:0,他引:1
Yon Dohn Chung 《Distributed and Parallel Databases》2008,23(3):207-234
The continuous partial match query is a partial match query whose result remains consistently in the client’s memory. Conventional
cache invalidation methods for mobile clients are record ID-based. However, since the partial match query uses content-based
retrieval, the conventional ID-based approaches cannot efficiently manage the cache consistency of mobile clients. In this
paper, we propose a predicate-based cache invalidation scheme for continuous partial match queries in mobile computing environments.
We represent the cache state of a mobile client as a predicate, and also construct a cache invalidation report (CIR), which
the server broadcasts to clients for cache management, with predicates. In order to reduce the amount of information that
is needed for cache management, we propose a set of methods for CIR construction (in the server) and identification of invalidated
data (in the client). Through experiments, we show that the predicate-based approach is very effective for the cache management
of mobile clients. 相似文献