Internet and IoT applications have generated increasing amounts of data that require efficient storage. Many persistent memory file systems have been designed to handle high-performance storage demands by fully exploiting the senior features of persistent memory (PM). However, PMs suffer from limited write endurance. Existing PM file systems achieve PM wear-leveling by designing wear-leveling-aware allocators. These allocators focus on providing higher-balanced writes to PMs while neglecting the overhead. Moreover, they cause serious request conflicts in parallel block requests by multiple threads in modern multiprocessor computer systems. In this paper, we propose an efficient wear-leveling-aware parallel allocator, WPAlloc, for persistent memory file systems to achieve wear-leveling of PM and high parallel performance. The essential idea of WPAlloc is to allocate blocks with lower write counters for each allocation request and to provide parallel block allocation and deallocation for multiple threads via one free list per logical processor. WPAlloc consists of two key techniques: the bucket sort-based range management scheme (BRMS) and the parallel allocation and deallocation scheme (PADS). First, we design the BRMS to obtain the less worn free blocks. Based on BRMS, an online wear range adjustment algorithm has been designed to adjust the wear range dynamically. Then, we present the PADS to avoid request conflicts by multiple threads. We implement WPAlloc based on PMFS. Experimental results show that WPAlloc can reduce the maximum write by 54.2%, 10.2%, and 55.7%, while achieving average performance improvements of 5.68%, 54.18%, and 11.28% compared to PMFS, DWARM, and WASA, respectively.

Emerging byte-addressable non-volatile memory (NVM) has the advantages of fast, cheap and persistent, and is considered as the next generation of persistent memory. However, existing NVM-based filesystems cannot adapt well for mobile devices, and not to mention the consideration for mobile application characteristics. In this paper, we propose an efficient and durable in-memory file system named as Mobi-PMFS for mobile devices. Proposed Mobi-PMFS is not only adaptive to ARM architecture, but also customized according to mobile application features. A wear-aware three-list space management scheme including a switching allocation algorithm is proposed to provide optimum performance for mobile systems while keeping the durability of NVM. Experimental results show that Mobi-PMFS is 8x times and 1.2x faster than EXT4-SSD and EXT4-DAX, and provides 11x wear-leveling improvement compared with the original PMFS.

Emerging file systems have been designed for fully exploring NVM's advanced features. However, with the development of big data, these file systems suffer from the performance degradation in highly concurrent environment, which are caused by serious access conflicts in space management. To solve this problem, we propose an efficient concurrency-oriented space management scheme named as COSMA. Along with novel data structure design, COSMA is able to greatly reduce request congestion among multiple threads through hierarchical space allocation scheme. Furthermore, COSMA provides 3 reclamation strategies to improve space utilization, and can also adapt to different systems which varied in NVM capacities. To ensure the system reliability, COSMA is capable of keeping wear leveling among multiple NVMs slots. We implement COSMA in a representative persistent file system, PMFS. Experimental results show that COSMA can improve the IOPS of PMFS by 15%, the write throughput of PMFS by 7.6% and the concurrent processing performance of PMFS by 50 %. Besides, it can also achieve wear-leveling among multiple NVMs.