NVMFS-IOzone: Performance Evaluation for the New NVMM-based File Systems

With the emerging of NVM (Non-Volatile Memories) technologies, NVMM-based (Non-Volatile Main Memories) file systems have attracted more and more attention. Compared to traditional file systems, most NVMM-based file systems bypass the page cache and the I/O software stack. With the new mmap interface known as the DAX-mmap interface (DAX: direct access), the CPU can access the NVMM much faster by loading from/storing to it directly. However, the existing file system benchmark tools are designed for traditional file systems and do not support the new features of NVMM-based file systems, so the returned results are very often not accurate. In this paper, a new benchmark tool called NVMFS-IOzone is proposed. The behavior of the tool is redesigned to reflect the new features of NVMM-based file systems. The NVM-lib from Intel is used instead of traditional msync() to keep data consistent when evaluating the performance of the DAX-mmap interface. Experimental results show that the new benchmark tool can reveal a hidden improvement of 1.4~2.1 times in NVMM-based file systems, which cannot be seen by the traditional evaluation tools. The data paths of direct load/store to NVMM and bypassing CPU cache are also provided to support the new ##features of NVMM-based file systems for multidimensional evaluation. Furthermore, embedded cleaning-ups has also been added to NVMFS-IOzone to support convenient evaluation consistency, which benefits both NVMM-based and non-NVMM-based file system benchmarking even for quick and casual tests. The whole experimental evaluation is based on real physical NVMs rather than simulated NVMs, and the experimental results confirm the effectiveness of our design.