面向非易失内存写优化的重计算方法

A Write-Optimized Re-computation Scheme for Non-Volatile Memory

非易失存储(non-volatile memory,NVM)技术的兴起给计算机存储系统带来了很多机遇与挑战.与DRAM相比,NVM作为持久性内存具有非易失、低能耗以及高存储密度等优点,但同时它也具有擦写次数有限以及写操作延迟高等缺点,故以NVM为内存的系统需要减少对内存的写操作,以提升NVM寿命和系统性能.为了解决这个问题,提出了基于结点出度的重计算方法(re-computation scheme based on the out degree of computing nodes,ROD),由于CPU与内存间的性能差距会导致CPU计算资源的浪费,为此ROD方法选择性地丢弃本需要存储到内存的计算结果,需要时再重新计算得到,利用计算换存储的方式减少写NVM的次数.实验采用powerstone测试集,在搭载了NVMain的Gem5模拟器中对ROD方法与贪心重计算方法和以存储为主导的无重计算方法做性能对比.结果表明ROD方法相比于存储主导的方法平均减少44.3%(最高68.5%)的写操作.ROD方法的运行耗时比存储主导的方法平均减少28.1%(最高68.6%),比贪心重计算的方法平均减少9.3%(最高19.4%).

The rise of non-volatile memory(NVM)technology brings many opportunities and challenges to computer storage systems.Compared with DRAM,NVM has the advantages of non-volatility,low energy consumption and high storage density as persistent memory.However,it has the disadvantages of limited erase write times and high write latency.Therefore,it is necessary to reduce the write operations to the non-volatile main memory to improve system performance and extend the lifetime of NVM.To address this problem,this paper proposes ROD,which is a re-computation scheme based on the out degree of computing nodes.Due to the performance gap between CPU and memory leading to computing resources waste,ROD selectively discards the computed results which should be stored into the NVM and re-computes them when needed.By swapping the storage with computation,ROD reduces the number of writes to the NVM.We have implemented ROD and evaluated it on Gem5 simulator with NVMain.We also implemented the greedy re-computation scheme and the store-only scheme as state-of-the-art work to be compared with ROD.Experimental results from powerstone benchmark show that ROD reduces write operations by 44.3%on average(up to 68.5%)compared with the store-only scheme.The execution time is reduced by 28.1%on average(up to 68.6%)compared with the store-only scheme,and 9.3%on average(up to 19.4%)compared with the greedy scheme.