RCC高速缓存一致性协议的带参验证

Godson-T众核处理器的RCC高速缓存一致性协议是一种非常有特色的带参并发系统,对此协议的带参验证是一个很大的挑战。 Cubicle是最近出现的基于SMT求解器的带参模型检测工具。我们使用了Cubicle带参模型检测工具,成功对RCC协议进行了建模和验证。实验结果表明, RCC协议在结点个数为任意规模时均满足协议的各种安全性质。     

Godson-T众核体系结构上的Broadcast性能优化

Godson-T是中国科学院计算技术研究所计算机系统结构重点实验室先进微系统组正在研制开发的适合于超深亚微米工艺实现的大规模片上众核系统.Godson-T片上存储的单端口结构节省了芯片面积但制约了共享数据的读取效率.直接在Godson-T上实现传统的Broadcast算法需要大量的同步互斥开销,无法达到很好的性能提升.基于Godson-T体系结构,对数据共享的重要并行算法Broadcast进行优化,提高了Godson-T体系结构下的数据共读的效率.主要采取了以下3项技术：消除大规模的线程同步,建立源地址到目的地址的映射表和用汇编语言实现Broadcast的核心部分.优化后Broadcast在小核数为32时即可达到5.8倍加速比.     

H.264去块滤波算法在众核结构上的并行优化

在H.264视频解码中,去块滤波是运算量很大的一部分.由于去块滤波过程中,数据之间存在复杂的依赖性,现有的很多去块滤波并行方案存在着并行度小、同步互斥开销大的缺点.本文结合去块滤波算法及众核处理器Godson-T的结构特性,提出了一种可以减少数据依赖的去块滤波算法并行优化方案.相对于以前的很多方法,此并行方案首先在算法上增大了并行度,减少了同步开销,同时,我们通过片上众核处理器Godson-T的硬件支持,采用计算与通信重叠等优化策略,使得优化后的算法达到了数倍的性能提升.     

Fast and scalable lock methods for video coding on many-core architecture

Many-core processors are good candidates for speeding up video coding because the parallelism of these applications can be exploited more efficiently by the many-core architecture. Lock methods are important for many-core architecture to ensure correct execution of the program and communication between threads on chip. The efficiency of lock method is critical to overall performance of chipped many-core processor. In this paper, we propose two types of hardware locks for on-chip many-core architecture, a centralized lock and a distributed lock. First, we design the architectures of centralized lock and distributed lock to implement the two hardware lock methods. Then, we evaluate the performance of the two hardware locks and a software lock by quantitative evaluation micro-benchmarks on a many-core processor simulator Godson-T. The experimental results show that the locks with dedicated hardware support have higher performance than the software lock, and the distributed hardware lock is more scalable than the centralized hardware lock.     

StreamTMC: Stream compilation for tiled multi-core architectures

Tiled multi-core architectures have become an important kind of multi-core design for its good scalability and low power consumption. Stream programming has been productively applied to a number of important application domains. It provides an attractive way to exploit the parallelism. However, the architecture characteristics of large amounts of cores, memory hierarchy and exposed communication between tiles have presented a performance challenge for stream programs running on tiled multi-cores. In this paper, we present StreamTMC, an efficient stream compilation framework that optimizes the execution of stream applications for the tiled multi-core. This framework is composed of three optimization phases. First, a software pipelining schedule is constructed to exploit the parallelism. Second, an efficient hybrid of SPM and cache buffer allocation algorithm and data copy elimination mechanism is proposed to improve the efficiency of the data access. Last, a communication aware mapping is proposed to reduce the network communication and synchronization overhead. We implement the StreamTMC compiler on Godson-T, a 64-core tiled architecture and conduct an experimental study to verify the effectiveness. The experimental results indicate that StreamTMC can achieve an average of 58% improvement over the performance before optimization.     

基于软硬件的协同支持在众核上对1-DFFT算法的优化研究

随着高性能计算需求的日益增加,片上众核(many-core)处理器成为未来处理器架构的发展方向.快速傅立叶变换(FFT)作为高性能计算中的重要应用,对计算能力和通信带宽都有较高的要求.因此基于众核处理器平台,实现高效、可扩展的FFT算法是算法和体系结构设计者共同面临的挑战.文中在众核处理器Godson-T平台上对1-D FFT算法进行了优化和评估,在节省几乎三分之一L2 Cache存储开销的情况下,通过隐藏矩阵转置,计算与通信重叠等优化策略,使得优化后的1-D FFT算法达到3倍以上的性能提升.并通过片上网络拥塞状况的实验分析,发现对于像FFT这样访存带宽受限的应用,增加L2 Cache的访问带宽,可以缓解因为爆发式读写带给片上网络和L2 Cache的压力,进一步提高程序的性能和扩展性.