ZonFS: A Storage Class Memory File System with Memory Zone Partitioning on Linux

초록

Recent developments in storage class memory such as PCM, MRAM, RRAM, and STT-RAM have strengthened their leadership as storage media for memory-based file systems. Traditional Linux memory-based file systems such as Ramfs and Tmpfs utilize the Linux page cache as a file system. These file systems, when adopted for SCM, have the following problems. First, current implementations of Ramfs and Tmpfs have no mechanism to explicitly allocate pages from specific memory. Second, memory pages allocated from SCM do not follow the Linux kernel's page allocation process exactly, resulting in unnecessary performance overhead. To resolve the aforementioned challenges, we propose the development of a new memory-based file system using Memory Zone Partitioning for SCM called ZonFS. ZonFS is implemented by extending the Linux Ramfs. In particular, we define a storage zone for SCM, modify the Ramfs to allocate a file system page from SCM. ZonFS avoids running unnecessary Linux VM kernel codes such as (i) inserting pages allocated from SCM into the LRU list for VM page replacement and (ii) checking dirty pages for write-back to disk. We also modify the Ramfs to allocate inode cache in SCM and eliminate the risk of inode cache loss in case of power failure. Extensive evaluations indicate that ZonFS has up to 9.1% and 14.1% higher I/O throughputs than native Ramfs and Tmpfs.