摘要:当前，大数据及人工智能技术向嵌入式系统发展，对嵌入式系统的存储访问能力提出了更高的要求.磁畴壁存储器凭借其高读写速度、高密度以及低功耗等优点，可以用于嵌入式系统，以满足数据密集型应用对访问速度、容量及能耗的需求.但是磁畴壁存储器在进行数据访问之前需要进行移动操作，这将极大影响其存储访问性能.而减少移动操作可以有效提升磁畴壁存储器的性能.面向运行数据密集型应用的多读/写头磁畴壁存储器系统，研究减少移动操作的最优指令调度与数据放置技术.首先提出了可获得最小移动次数的整数线性规划（integer linear programming，简称ILP）模型.由于ILP模型不能在多项式时间内求得最优解，所以提出了多项式时间的启发式算法——生成指令调度和数据放置（generation instruction scheduling and data placement，简称GISDP）算法.实验结果表明，ILP模型和GISDP算法可以有效减少移动操作的次数.在配备8个读/写头的磁畴壁存储器上，GISDP算法生成的指令调度与数据放置方案相较其他算法可以平均减少89.7%的移动操作，并且GISDP算法的结果接近ILP模型的最优解.



Abstract:Nowadays, it has become a trend that embedded systems are designed for big data and artificial intelligence applications, which demand the large capacity and high access performance of memory. Domain wall memory (DWM) is a novel non-volatile memory with high access performance, high density, and low power consumption. Thus, for data-intensive applications specific embedded systems, DWM can meet the requirements of access speed, capacity, and power consumption. However, before accessing data on DWM, data in nanowires need to be shifted to align them with read/write port, which is called shift operation. Numerous shift operations take most of time and generate much quantity of heat when accessing data on DWM. It will decrease the access speed of DWM and system performance further. In that case, reducing shift operations of DWM can significantly improve the system performance. This study aims at data-intensive application specific embedded systems with multi-port DWM, and explores optimal instruction schedule and data placement strategy which achieve minimum shift operations. An integer linear programming (ILP) model is firstly proposed to obtain minimum number of shifts. Since ILP model cannot find the optimal solution in polynomial time, a heuristic algorithm is proposed to reduce the number of shifts on DWM—generation instruction scheduling and data placement (GISDP) algorithm. The experimental results show that ILP model and GISDP algorithm can effectively reduce shift operation. On target system with 8 read/write ports DWM, GISDP can reduce shift operations by 89.7% on average when compared with other algorithms, and the results of GISDP are close to the optimal solutions of ILP.



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