微型温差电池的无线传感器节点自供电系统

伴随全球性的能源危机,利用环境中的动态能量为无线传感器网络供电已经成为一种趋势.本文设计了一个基于BQ25504芯片的无线传感器节点自供电系统,该系统可以在330mV电压下启动,在工作时以最大功率跟踪方式采集低至80 mV的温差能量,并能够动态地将能量通过能量缓冲器电路供给无线传感器节点使用.该系统有效地解决了基于微型温差电池的无线传感器节点自供电的问题.     

Reducing cache and TLB power by exploiting memory region and privilege level semantics

The L1 cache in today’s high-performance processors accesses all ways of a selected set in parallel. This constitutes a major source of energy inefficiency: at most one of the N fetched blocks can be useful in an N-way set-associative cache. The other N-1 cachelines will all be tag mismatches and subsequently discarded.We propose to eliminate unnecessary associative fetches by exploiting certain software semantics in cache design, thus reducing dynamic power consumption. Specifically, we use memory region information to eliminate unnecessary fetches in the data cache, and ring level information to optimize fetches in the instruction cache. We present a design that is performance-neutral, transparent to applications, and incurs a space overhead of mere 0.41% of the L1 cache.We show significantly reduced cache lookups with benchmarks including SPEC CPU, SPECjbb, SPECjAppServer, PARSEC, and Apache. For example, for SPEC CPU 2006, the proposed mechanism helps to reduce cache block fetches from the data and instruction caches by an average of 29% and 53% respectively, resulting in power savings of 17% and 35% in the caches, compared to the aggressively clock-gated baselines.     

存储器行缓冲区命中预测研究

存储系统已经成为提高计算机系统性能的一个瓶颈.现利用DRAM存储器的访问特性来减少存储器访问操作的平均延迟.首先对存储器行缓冲区的控制策略进行研究,提出了读写分离式页模式预测器,并提出了双饱和计数器预测器和2级预测器等两种预测器方案;然后以SimpleScalar搭建的仿真平台对提出的预测方案进行了性能评估.结果显示,与缓冲区"关"策略相比,平均访问延迟减少了26%,IPC平均提高了4.3%;与缓冲区"开"策略相比,平均访问延迟减少了19.6%,IPC平均提高了2.5%.     

ORACLE数据库SQL优化原则

Oracle数据库是当前应用最广泛的大型数据库之一,其系统结构复杂,性能受多方面因素影响,其中SQL语句的执行效率是影响其性能的关键因素。以一个省级通信运营商的ORACLE ERP系统为例,从ORACLE数据库的SQL共享原理和SQL执行过程入手,指出合理配置数据库参数,提高SQL语句共享、提高数据缓存命中率是SQL语句性能提高的前提;并在此基础提出了SQL语句优化的四个原则。     

体检系统中尿液检查接口的设计与实现

在尿常规检查中,将检查结果自动上传到体检数据库,这不仅可以提高工作效率、服务质量还可以提升医院体检工作的信息化管理水平。在接口设计的时候,通过对传统串口数据接收方法进行分析,结合数据缓存思想,提出一种基于缓冲区的实时串口数据接收方法,同时采用多线程技术实现FA-200型尿液分析仪数据的批量接收。本设计在我校医院一年多的体检中得到了有效的验证,实现了预期的目标。     

TB级地形数据实时漫游核心算法研究

TB级数据时代已经到来,如何有效地在普通PC机上实现TB级地形数据漫游,已逐渐成为GIS（地理信息与系统）学术界的研究热点。海量数据组织管理是3维地形数据漫游的核心机制,传统四叉树、八叉树等数据结构,一定程度上解决绘制瓶颈问题,但是结构复杂,很难适应TB级地形场景实时、稳定的漫游需求。通过实施多级缓冲机制、采用动态LOD（levels of detail）与显存调度技术,以及引入多核CPU并行计算策略,最终构建出一套与数据大小无关的实时地形绘制算法。通过对1 GB、10 GB、200 GB、500 GB级等海量数据进行实验,平均绘制速率可达到30帧/s以上,比一般算法高出23倍,从而验证本文算法的实用性。     

Performance enhancement of TCP in high-speed networks

GridFTP is a secure and reliable high-performance parallel data transfer protocol used for transferring massive amounts of widely distributed data. Currently it allows users to configure the number of parallel streams and socket buffer size. However, its tuning procedure for optimal combination is a time consuming task. The socket handlers and buffers are important system resources and must therefore be carefully managed. In this paper, we propose a scheme to achieve high throughput even with a smaller buffer size, and also derive a regression equation to predict the optimal combination of resources for a connection. To improve the performance, the TCP based on our scheme obtains higher throughput and spends less memory for the same throughput than the original TCP scheme. In addition, the regression equation is verified by comparing measured and predicted values, and we apply the equation to an actual experiment on the KOrea advanced REsearch Network (KOREN). The result demonstrates that the equation provides excellent predictions with only an 8% error boundary.     

Determination of optimal size of the de-jitter buffer of a receiving router

The influence of the size of the de-jitter buffer of a receiving router and of the network load on the transmission quality of voice traffic is investigated by means of simulation modeling. The optimal size of the de-jitter buffer that supports an acceptable level of loss of voice packets and a propagation time of the voice signal that corresponds to accepted standards is determined.     

一种高效嵌入式协议栈缓冲区管理机制

提出一种MYBUF高效嵌入式协议栈两级缓冲区管理机制,该机制基于内存保护模式,具有可配置性,支持静态、动态分配和回收.使用该缓冲区管理机制可使嵌入式TCP/IP协议栈各层之间实现零拷贝数据传递.在基于自主开发的HDTV(High Definition Television)双向系统平台上的测试结果表明,该管理机制完全满足嵌入式系统网络通信的应用需求,是一种高效、简洁、可靠的缓冲区管理机制.不失一般性,本文设计的MYBUF缓冲区管理机制可适用于其它嵌入式网络通信系统.     

基于状态图的缓冲区溢出攻击分析

结合缓冲区溢出攻击产生的原理,分析缓冲区溢出攻击代码的结构,论述Snort规则对缓冲区溢出攻击的检测,在此基础上构建一个基于状态图的缓冲区溢出攻击的分析模型。该模型对于进一步明确缓冲区溢出攻击过程和完善缓冲区溢出攻击的检测和防御有很大的理论和实际意义。