PLock: A Fast Lock for Architectures with Explicit Inter-core Message Passing

Abstract

Synchronization is a significant issue for multi-threaded programs. Mutex lock, as a classic solution, is widely used in legacy programs and is still popular for its intuition. The SW26010 architecture, deployed on the supercomputer Sunway Taihulight, introduces hardware-supported inter-core message passing mechanism and exposes explicit interfaces for developers to use its fast on-chip network. This emerging architectural feature brings both opportunities and challenges for mutex lock implementation. However, there is still no general lock mechanism optimized for architectures with this new feature. In this paper, we propose pLock, a fast lock designed for architectures that support Explicit inter-core Message Passing (EMP). pLock uses partial cores as lock servers and leverages the fast on-chip network to implement high-performance mutual exclusive locks. We propose two new techniques - chaining lock and hierarchical lock - to reduce message count and mitigate network congestion. We implement and evaluate pLock on an SW26010 processor. The experimental results show that our proposed techniques improve the performance of EMP-lock by up to 19.4× over a basic design.