Research On Persistent Memory File System Optimization

Emerging byte-addressable non-volatile memories(NVMMs)offer performance close to DRAM with data persistence,promoting them to be used as persistent memory.However,due to the characteristics of persistent memory,the traditional management methods of memory and storage is not suitable for it,it is a new challenge to manage the persistent memory,to be compatible with the existing applications,reduce the cost and improve the performance of the system.The state-of-the-art NVM-based file systems utilize the characteristic that the persistent memory can be directly accessed by the central processing unit(CPU)to construct a page table,mapping process virtual address to physical address of the persistent memory.Users thus can bypass cache and directly get access to the memory-mapped file on the persistent memory.But this still causes huge cost due to page fault,affecting the performance of NVM-based file system.To address the issue above,we propose mapping structure unified memory-mapped file mechanism.The new memory-mapped file mechanism combines the advantages of memory page table and file data block index,and adopts the page-table-structure-based file data index as the unified address mapping structure,thus avoid the trigger of page fault during the file access and improves the file access performance.we designed a memory map method that reuse the mapping structure,to migrate the file data index into page table and construct a address mapping relation during memory map process,a fast unmap method,to efficiently release the address mapping structure,a new mapping option and a virtual memory flag,to enable the use of mapping-structure-unified memory map method and fast unmap method through legacy interface by the user process.Using a persistent memory emulator,we evaluated the performance of mapping-structure-unified memory-mapped file with several workloads.The result shows that the new structure and methods can effectively improve the read and write performance of the memory-mapped file,reduce the time of memory map release and reduce the space consumption of the addressing structure in the read and write process of the memory-mapped file compared to the page fault management method.