Designing And Improving The Hybrid PCM&DRAM-Based Memory System For Smartphones

With the rapid development of Mobile Internet,mobile devices have been popular.The performance demand of mobile devices such as smartphones has also been increased.Among these,the demand of faster speed,larger capacity for the memory brings opportunities and challenges for smartphone memory system.Traditional memory based on DRAM faces severe challenges in terms of craft size,energy consumption.The new NonVolatile Memory(NVM)such as Phase Change Memory(PCM)has advantages of large capacity,low power consumption and non-volatility,and its performance of read & write is close to DRAM.It provides some new ideas for the design and improvement of memory system.In order to further increase the capacity of memory without reducing its performance,PCM has been introduced to build the memory system with DRAM.It could overcome the limitation of the write performance and endurance of PCM and remedy the defect of DRAM refresh power consumption.In addition,there are two phenomena existing in smartphones should be considered when designing the system: the large amount of writes force writing the data from memory to flash frequently;a large number of I/O accesses from background applications diminishes the efficiency of memory access from foreground applications.In conclusion,“vertical” layered hybrid memory architecture based on PCM&DRAM is chosen.In this architecture,DRAM is the Cache of PCM and PCM is the main memory with large capacity.And designing request scheduling schemes of read & write and a background flush strategy to improve the I/O performance of smartphones,which relatively forms a complete solution for hybrid memory system.Simulation,test and analysis has been conducted.The experimental results show that with the proposed mechanisms,“vertical” layered hybrid memory architecture based on PCM&DRAM could alleviate the performance limitation of current memory system,improve the I/O efficiency,and then confirms its viability.