嵌入式实时内存数据库故障恢复技术

故障发生后,迅速而有效地恢复对数据库系统而言是至关重要的。本文针对嵌入式实时内存数据库的特征,结合一个具体的嵌入式实时内存数据库系统（ARTs—EDB）,给出了相应基于日志的恢复策略和实现技术。     

Acceleration of Simulated Fault Injection Using a Checkpoint Forwarding Technique

Simulated fault injection (SFI) is widely used to assess the effectiveness of fault tolerance mechanisms in safety‐critical embedded systems (SCESs) because of its advantages such as controllability and observability. However, the long test time of SFI due to the large number of test cases and the complex simulation models of modern SCESs has been identified as a limiting factor. We present a method that can accelerate an SFI tool using a checkpoint forwarding (CF) technique. To evaluate the performance of CF‐based SFI (CF‐SFI), we have developed a CF mechanism using Verilog fault‐injection tools and two systems under test (SUT): a single‐core‐based co‐simulation model and a triple modular redundant co‐simulation model. Both systems use the Verilog simulation model of the OpenRISC 1200 processor and can execute the embedded benchmarks from MiBench. We investigate the effectiveness of the CF mechanism and evaluate the two SUTs by measuring the test time as well as the failure rates. Compared to the SFI with no CF mechanism, the proposed CF‐SFI approach reduces the test time of the two SUTs by 29%–45%.     

The Culture of the Copy

Is copying necessarily a bad thing? Theorists from Walter Benjamin to Richard Dawkins, and from Judith Butler to Homi Bhabha, have suggested not. Drawing on their work, Neil Leach , Professor of Digital Design at the European Graduate School and Visiting Professor at Harvard Graduate School of Design, challenges the notion of authenticity and argues that the entire history of human culture is built on a constant process of replication.     

Gallic acid induces G2/M phase cell cycle arrest via regulating 14‐3‐3β release from Cdc25C and Chk2 activation in human bladder transitional carcinoma cells

Scope: Cell cycle regulation is a critical issue in cancer treatment. Previously, gallic acid (GA) has been reported to possess anticancer ability. Here, we have evaluated the molecular mechanism of GA on cell cycle modulation in a human bladder transitional carcinoma cell line (TSGH‐8301 cell). Methods and results: Using flow cytometer analysis, exposure of the cells to 40 μM GA resulted in a statistically significant increase in G2/M phase cells, which was accompanied by a decrease in G0/G1 phase cells. GA‐treated cells resulted in significant growth inhibition in a dose‐dependent manner accompanied by a decrease in cyclin‐dependent kinases (Cdk1), Cyclin B1, and Cdc25C, but significant increases in p‐cdc2 (Tyr‐15) and Cip1/p21 by western blotting. Additional mechanistic studies showed that GA induces phosphorylation of Cdc25C at Ser‐216. This mechanism leads to its translocation from the nucleus to the cytoplasm resulting in an increased binding with 14‐3‐3β. When treated with GA, phosphorylated Cdc25C can be activated by ataxia telangiectasia‐mutated checkpoint kinase 2 (Chk2). This might be a DNA damage response as indicated by Ser‐139 phosphorylation of histine H2A.X. Furthermore, treatment of the cells with a Chk2 inhibitor significantly attenuated GA‐induced G2/M phase arrest. Conclusion: These results indicate that GA can induce cell cycle arrest at G2/M phase via Chk2‐mediated phosphorylation of Cdc25C in a bladder transitional carcinoma cell line.     

实时数据库系统的内存数据库组织与故障恢复

本文给出一种在内存数据库中能有效节约内存空间的数据组织结构--内存数据库图(MMDBG),然后给出MMDBG的物理组织形式.并重点讨论了基于MMDBG的事务恢复和系统恢复算法,在最大程度上提高系统的响应时间和支持实时事务.     

支持文件迁移的Linux检查点机制的实现

在BLCR系统的基础上实现一种支持进程打开文件迁移的检查点机制,给出该机制的总体框架、关键技术、进程打开文件保存恢复、状态保存和恢复的流程。实验结果表明,该机制支持多线程、信号、进程打开文件及管道等的保存与恢复,无需重编译内核,对用户具有良好的透明性。     

Linux下系统V共享内存的保存与恢复

设置检查点是保存和恢复进程运行状态的一种重要技术,是实现容错、卷回调试和进程迁移的重要手段。本文研究了全透明检查点系统Epckpt在系统Ⅴ共享内存方面的实现方法和不足,给出了自己的改进,从而更好地实现了系统Ⅴ共享内存的保存与恢复。     

基于异步消息记录(CMLA)的卷回恢复算法

为了最大限度地减少检测点设置和卷回恢复的时间，空间开销，提出了基于异步消息记录的卷回恢复算法，同以前的算法相比较，该算法一方面节省了用于进程之间同步的时间开销，另一方面检测点设置及卷回过程中只涉及少量的相关进程，并且减少了保存检测点的空间开销，文中对算法的正确性进行了证明，并通过模拟实验给出了算法的开销。     

Checkpointing algorithms and fault prediction

This paper deals with the impact of fault prediction techniques on checkpointing strategies. We extend the classical first-order analysis of Young and Daly in the presence of a fault prediction system, characterized by its recall and its precision. In this framework, we provide optimal algorithms to decide whether and when to take predictions into account, and we derive the optimal value of the checkpointing period. These results allow us to analytically assess the key parameters that impact the performance of fault predictors at very large scale.     

工作流系统适应性检查点机制的研究

容错技术已经成为工作流的研究热点,设置检查点是一种常用的容错方法。针对工作流系统提出一种适应性检查点机制,该机制通过最优化检查点数量和动态设置检查点间隔,大大提高了错误发生情况下任务按时完成的比率,并通过实验验证了该机制优于传统的检查点机制。