Research And Implementation Of Optimization Method For NVM-DRAM Hybrid Memory System

Non-Volatile Memory(NVM)is a new type of random access memory witch has developed rapidly in recent years.The advantages of NVM,such as high storage density,low power consumption,fast read/write speed and non-volatile,have attracted many researchers to study the application of nonvolatile memory(NVM)in computer systems,for example,using NVM to replace the traditional memory directly or in combination with traditional memory for a hybrid-memory to instead the main memory.However,NVM also has many drawbacks,for example,the write latency of NVM is nearly 10 times more than that of DRAM,and the lifetime of NVM is far less than DRAM,thus NVM is not suitable for direct instead of DRAM as main memory and is more suitable for combining with DRAM to be the main memory in the computer system.Therefore,this paper aims to control the memory access operations in the NVM-DRAM hybrid main memory system,to effectively reduce the write times of NVM,extend the lifetime of NVM,reduce the power consumption of the system and guarantee the consistency of the system.Firstly,this thesis proposes a new memory management algorithm,called DMA(Dynamic Measure Allocation).DMA is an algorithm which can evenly distribute store locations for the programs with different pressure of writes,and it moves the programs with high pressure of writes to DRAM for enhancing NVM lifetime,meanwhile,it also can reduce the number of writes on NVM.The basic idea of DMA is periodically move the programs with high pressure of writes from NVM to DRAM and keep the others in NVM.According to the experimental results,DMA can reduce the number of writes on NVM by 40%?60% compared with the case without this algorithm.Furthermore,this result also proves that DMA is able to extend NVM lifetime for DRAM-NVM hybrid main memory systems.Besides,this thesis presents a page replacement method based on NVM-DRAM hybrid main memory system for low power and consistency guarantees,called EAPR(Energy-Aware Page Replacement).EAPR is based on NVM-DRAM hybrid main memory architecture,and it analyzed the features of energy consumption during migrating the pages between DRAMs and NVMs.Meanwhile,this thesis also presents an improved transaction scheme for satisfying the consistency guarantees when system failure occurred.The energy consumption of page access in DRAMs and NVMs can be calculated according to the memory access,and the pages are migrated according to their energy consumption,by which the pages are determined to migrate from NVM to DRAM or from DRAM to NVM to satisfy low power.Furthermore,EAPR guarantees the consistency of the hybrid memory architecture by optimizing the structure of logs after the transactions of the applications are submitted.Finally,the experimental results show that EAPR can not only reduce the energy consumption but also guarantee the consistency of transactions in the NVM-DRAM hybrid memory system.