Exploiting superpages in a nonvolatile memory file system

Abstract

Emerging nonvolatile memory technologies (sometimes referred as Storage Class Memory (SCM)), are poised to close the enormous performance gap between persistent storage and main memory. The SCM devices can be attached directly to memory bus and accessed like normal DRAM. It becomes then possible to exploit memory management hardware resources to improve file system performance. However, in this case, SCM may share critical system resources such as the TLB, page table with DRAM which can potentially impact SCM's performance. In this paper, we propose to solve this problem by employing superpages to reduce the pressure on memory management resources such as the TLB. As a result, the file system performance is further improved. We also analyze the space utilization efficiency of superpages. We improve space efficiency of the file system by allocating normal pages (4KB) for small files while allocating super pages (2MB on ×86) for large files. We show that it is possible to achieve better performance without loss of space utilization efficiency of nonvolatile memory.