Parallelizing Shared File I/O Operations of NVM File System for Manycore Servers

NOVA, a state-of-the-art non-volatile memory (NVM) file system, has limited performance due to its coarse-grained per-file lock when multiple threads perform I/Os to a shared file in a manycore environment. For instance, a writer lock blocks other threads attempting to access the same file, although they access different regions of a file. When multiple threads reading the same file share a cache line containing a reader counter, performance can be significantly degraded due to cache consistency protocol as we increase the number of readers. This paper proposes a fine-grained segment-based range lock (SRL) that divides a file into multiple segments and manages a lock variable dynamically for each segment. Consequently, write operations can be parallelized without blocking unless there is a conflict in accessing the same range in a file. Moreover, SRL maintains a reader counter per segment that allows multiple reader threads to perform read operations without causing a performance bottleneck. We evaluated an SRL-based NOVA on an Intel Optane DC persistent memory (PM) manycore server. The benchmarking results showed that the average write throughput of the SRL-based NOVA is $3\times $ higher than the original NOVA, and the average read throughput scales linearly, while the original NOVA does not scale.