A stealing mechanism for delegation methods

Modern multi-core architectures exhibit non-uniform memory access (NUMA) behavior, where access by a core to data cached locally on a NUMA node is much faster than access to data cached on a remote node. Prior work has shown that on the NUMA multi-core system, delegation is the highly efficient solution to address the generally poor performance of locking methods on highly contended locks due to delegating the execution of critical section to one thread, reducing the movement of shared data between cores. However, we observe that delegation methods exhibit sub-par single-thread performance due mainly to the overheads of the communication between the server and client threads and request array traversal. To address this problem, this paper proposes a stealing mechanism that under no contention the clients can directly enter the critical section by enabling lock stealing. Meanwhile, under contention it employs delegation protocol by disabling lock stealing. Furthermore, we apply stealing mechanism to the state-of-the-art delegation methods: FFWD and RCL. The evaluation shows that delegation augmented with lock stealing can significantly improve the performance in the non-contended case, while matching the performance of their original counterparts in the contended circumstances.