Optimizing a FIFO, scalable spin lock using consistent memory

Abstract

The paper presents a FIFO queue based, scalable spin lock (FSSL) that: (1) uses only one atomic swap operation; (2) is scalable as it requires a constant amount of communication; (3) runs without a coherent cache support; and (4) provides a timing guarantee suitable for real time applications. The algorithm is optimal in the number of atomic operations required to solve the scalable mutual exclusion problem in NUMA architectures, improving on T. Craig's (1993) spin lock that uses four atomic swap operations. The FSSL algorithm minimizes the number of atomic operations by replacing them with non atomic read and write operations, and takes good advantage of recent multiprocessors where non atomic memory operations are much more optimized than atomic operations. The algorithm runs correctly in various weakly consistent memories, providing a potentially significant speedup over algorithms with more atomic operations.