Energy And Endurance Optimizations For Morphable Resistive Memory Page In Mobile Terminals

With the development of cloud computing,internet of things and edge computing,smart devices are becoming increasingly important.Traditional dynamic random-access memory(DRAM)in smart devices has a lot of disadvantages,such as high energy consumption,poor scalability and low reliability,which limit the development of smart devices.In order to solve these issues,energy-efficient morphable resistive memories,such as phase change memory,have emerged as promising alternatives to DRAM in smart devices.Morphable resistive memories have excellent features,included high density,zero leakage power and near DRAM performance.However,its high-density multiple-level cells(MLC)of morphable resistive memories incurs higher energy overhead compared with its single-level cell(SLC).Moreover,it can only sustain a limited number of write operations.Therefore,this thesis focuses on energy and endurance optimizations for morphable resistive memory.The main contributions are listed as follow.1.Morphable resistive memories can build multiple-level cells(MLC)to achieve high density and capacity,but this comes with the price of higher energy compared with SLC.Considering with the access pattern of special applications on smart devices,this thesis proposes a benefit model of SLC/MLC page conversion to dynamically adjust the number of SLC/MLC pages.The basic idea is to store the frequently accessed data in the SLC pages in order to reduce memory access latency.And the infrequently accessed data are stored in the MLC pages to expand the memory capacity,reduce the cost of page fault.2.Morphable resistive memories only sustain a limited number of write operations,the mode of MLC further reduces its endurance.Considering with the historical writing information of the MLC memory page,a novel and simple wear leveling method of MLC pages is proposed.The basic idea is to combine the write-biased-LRU algorithm and the structure of min heap on page management to improve the lifetime of MLC,while ensuring the efficiency of the application.In summary,the proposed techniques in this thesis can effectively reduce memory page faults,improve the efficiency of program execution,balance the distribution of write operations,and improve the lifetime of nonvolatile memory.