HybridTCache:一种基于专用事务Cache的软硬件协同事务内存系统

文中提出一种高效的软硬件协同事务内存系统HybridTCache.在通常情况下,事务完全由硬件执行,当事务大小超出了硬件限制时,操作系统将协同硬件执行.HybridTCache提出了一种新的专用事务Cache,称为TCache,缓存事务执行过程中的临时数据,由操作系统协同管理TCache溢出.文中给出了基于GEMS模拟器的HybridTCache原型系统.系统的评测显示HybridTCache比传统系统在性能、可扩展性、设计复杂度方面有较好的改进.     

基于C#语言的事务内存系统

事务内存是一种新的易于使用的同步技术,能使多线程程序高效地并行执行,目前大多数事务内存系统都处于研究实验阶段,尚未具备实际应用价值,或需要依赖特殊硬件实现。针对该现状,提出一种利用C#语言设计与实现的纯软件的事务内存系统,包括事务对象定义以及对事务对象的并行访问方法,并给出处理事务冲突的策略。实验结果表明,该系统是一种高效简洁的同步实现机制。     

集群上软件事务内存的层次化冲突检测

大多数事务内存研究都在多核处理器上进行,只有少数研究针对集群计算环境。现有的集群事务内存性能较差,因为事务内存的运行需要进行大量的远程内存访问,而集群的内存分布性使得远程内存访问的性能较差。事务内存运行中的冲突检测是进行远程内存访问最多的操作。我们提出了一种层次化的冲突检测方法,将其分为两个步骤进行,这种层次化的策略可以使集群上的软件事务内存获得高性能。     

Helenos: A realistic benchmark for distributed transactional memory

Transactional memory (TM) is an approach to concurrency control that aims to make writing parallel programs both effective and simple. The approach has been initially proposed for nondistributed multiprocessor systems, but it is gaining popularity in distributed systems to synchronize tasks at large scales. Efficiency and scalability are often the key issues in TM research; thus, performance benchmarks are an important part of it. However, while standard TM benchmarks like the Stanford Transactional Applications for Multi‐Processing suite and STMBench7 are available and widely accepted, they do not translate well into distributed systems. Hence, the set of benchmarks usable with distributed TM systems is very limited, and must be padded with microbenchmarks, whose simplicity and artificial nature often makes them uninformative or misleading. Therefore, this paper introduces Helenos, a realistic, complex, and comprehensive distributed TM benchmark based on the problem of the Facebook inbox, an application of the Cassandra distributed store.     

Automated dynamic detection of busy–wait synchronizations

With the advent of multicores, multithreaded programming has acquired increased importance. In order to obtain good performance, the synchronization constructs in multithreaded programs need to be carefully implemented. These implementations can be broadly classified into two categories: busy–wait and schedule‐based. For shared memory architectures, busy–wait synchronizations are preferred over schedule‐based synchronizations because they can achieve lower wakeup latency, especially when the expected wait time is much shorter than the scheduling time. While busy–wait synchronizations can improve the performance of multithreaded programs running on multicore machines, they create a challenge in program debugging, especially in detecting and identifying the causes of data races. Although significant research has been done on data race detection, prior works rely on one important assumption—the debuggers are aware of all the synchronization operations performed during a program run. This assumption is a significant limitation as multithreaded programs, including the popular SPLASH‐2 benchmark have busy–wait synchronizations such as barriers and flag synchronizations implemented in the user code. We show that the lack of knowledge of these synchronization operations leads to unnecessary reporting of numerous races. To tackle this problem, we propose a dynamic technique for identifying user‐defined synchronizations that are performed during a program run. Both software and hardware implementations are presented. Furthermore, our technique can be easily exploited by a record/replay system to significantly speedup the replay. It can also be leveraged by a transactional memory system to effectively resolve a livelock situation. Our evaluation confirms that our synchronization detector is highly accurate with no false negatives and very few false positives. We further observe that the knowledge of synchronization operations results in 23% reduction in replay time. Finally, we show that using synchronization knowledge livelocks can be efficiently avoided during runtime monitoring of programs. Copyright © 2009 John Wiley & Sons, Ltd.     

基于布隆过滤器的事务存储架构中的高速缓存

在基于硬件的事务存储多核处理器中,高速缓存具有暂存事务执行结果、检测事务间冲突以及当发生冲突时解决冲突的功能,是系统的核心模块.为了简化上述功能,研究并设计了一种基于布隆过滤器的高效缓存结构,提升了事务的执行效率,并且新增的硬件开销也比较小.     

一种硬件事务存储系统模拟环境的研究与实现

针对事务存储技术研究中的模拟实验问题,实现了一种专门用于硬件事务存储系统的模拟环境,该模拟环境采用执行驱动模拟方式,支持全系统模拟,利用系统结构模拟器Simics和多核扩展包GEMS实现多核处理器相关部件的功能和性能模拟,在此基础上扩展实现硬件事务存储系统各部件的建模和模拟,以模块化的方法支持多种事务存储系统的模拟实验和性能评价.论文在分析事务存储和系统结构模拟技术的基础上,讨论了事务存储系统模拟环境的设计思路和方案,给出了该模拟环境的组成结构,并通过一种目标事务存储系统结构和一组测试程序对模拟环境进行了实验测试.     

基于事务性执行的投机并行多线程软件模拟

基于事务性执行的投机并行多线程是一种适合未来多核微处理器架构的新型并行程序设计和编译技术.但在此基础上的并行程序执行过程更为复杂,程序执行过程的模拟成为关键问题之一.本文提出利用二进制代码级动态插桩技术对投机并行多线程程序进行功能性模拟,设计并实现了完整的软件平台,可精确地模拟和监控并行程序的线程级投机执行过程,检测访存冲突,从而实现投机并行多线程的语义.该软件平台同时可以作为进一步研究投机多线程并行程序真实执行过程的基础,并有效支持投机并行多线程编译器的设计和分析.     

事务存储研究

为了研究多核处理器系统上的并行编程问题,开展了对事务存储模型的研究.阐述了事务存储,介绍了事务存储系统的实现方法,利用4种事务存储系统详细阐述了事务存储的实现;重点讨论了6种影响事务存储发展的关键技术,即实现方式、数据结构组织、并发控制,冲突检测、争用管理等;提出了事务存储将向着软硬件结合、提升性能、提高正确性和满足多核应用需求的方向发展.     

事务存储系统中PGHB冲突检测算法研究

事务存储系统是一种全新的多核体系结构,为并行编程提供了一个简洁高效的编程环境。基于Signature的冲突检测算法是事务存储系统中很有前景的一种冲突检测方法,其误判率直接影响系统性能。GHB算法是一种优秀的冲突检测算法,具有较低的误判率,但硬件实现开销较大。本文对GHB冲突检测算法进行进一步改进,提出了一种PGHB算法。与GHB算法相比,PGHB算法在硬件开销和误判率两者之间取得了更好的折衷。