A NUMA-Aware Recoverable Mutex Lock

The mutual exclusion (ME) problem has been of interest to the scientific community since it was first defined by Dijkstra. Various algorithms have been developed to solve the problem, like the MCS and CLH queue-based locks. The problem was generalized into the recoverable mutual exclusion (RME) problem by Golab and Ramaraju to accommodate the possibility of process crash failures. Since then, multiple RME algorithms have been presented in the literature that vary in design and performance. Furthermore, non-uniform memory access (NUMA) architecture has become mainstream in designing modern distributed systems, stimulating the development of NUMA-aware mutex locks. None of the existing NUMA-aware mutex locks are recoverable to the best of our knowledge. In addition, none of the transformation techniques in the literature, such as flat-combining and cohort-locking, is a black-box transformation. Precisely, each of the existing transformation techniques requires specific characteristics of, and possible modifications to, the underlying NUMA-oblivious lock. In this work, we propose the Recoverable Filter (RF) lock, a black-box transformation approach that exploits memory locality to transform a NUMA-oblivious recoverable mutex lock into a NUMA-aware one. Practical experiments are conducted using two existing RME algorithms, Golab and Hendler's (GH) and Jayanti, Jayanti, and Joshi's (JJJ). The two RME locks are transformed into NUMA-aware locks using the proposed RF and the existing cohort algorithms. Results show that, in multi-socket configurations, our transformation boosts the performance of the NUMA-oblivious RME locks by up to 45%. The RME locks transformed using the proposed RF lock are slower than their non-recoverable cohort variants by up to 9%. Outcomes demonstrate that the overhead of our algorithm is minimal when using a single socket. Moreover, a deeper empirical assessment shows that the gap in performance between GH and JJJ is due to the entry section of JJJ, not its exit section.