Lock-based synchronization for GPU architectures

Abstract

Modern GPUs have shown promising results in accelerating compute-intensive and numerical workloads with limited data sharing. However, emerging GPU applications manifest ample amount of data sharing among concurrently executing threads. Often data sharing requires mutual exclusion mechanism to ensure data integrity in multithreaded environment. Although modern GPUs provide atomic primitives that can be leveraged to construct fine-grained locks, the existing GPU lock implementations either incur frequent concurrency bugs, or lead to extremely low hardware utilization due to the Single Instruction Multiple Threads (SIMT) execution paradigm of GPUs. To make more applications with data sharing benefit from GPU acceleration, we propose a new locking scheme for GPU architectures. The proposed locking scheme allows lock stealing within individual warps to avoid the concurrency bugs due to the SMIT execution of GPUs. Moreover, it adopts lock virtualization to reduce the memory cost of fine-grain GPU locks. To illustrate the usage and the benefit of GPU locks, we apply the proposed GPU locking scheme to Delaunay mesh refinement (DMR), an application involving massive data sharing among threads. Our lock-based implementation can achieve 1.22x speedup over an algorithmic optimization based implementation (which uses a synchronization mechanism tailored for DMR) with 94% less memory cost.