NUDA: A Non-Uniform Debugging Architecture and non-intrusive race detection for many-core

Traditional debug methodologies are limited in their ability to provide debugging support for many-core parallel programming. Synchronization problems or bugs due to race conditions are particularly difficult to detect with software debugging tools. Most traditional debugging approaches rely on globally synchronized signals, but these pose problems in terms of scalability. The first contribution of this paper is to propose a novel non-uniform debug architecture (NUDA) based on a ring interconnection schema. Our approach makes debugging both feasible and scalable for many-core processing scenarios. The key idea is to distribute the debugging support structures across a set of hierarchical clusters while avoiding address overlap. This allows the address space to be monitored using non-uniform protocols. Our second contribution is a non-intrusive approach to race detection supported by the NUDA. A non-uniform page-based monitoring cache in each NUDA node is used to watch the access footprints. The union of all the caches can serve as a race detection probe. Using the proposed approach, we show that parallel race bugs can be precisely captured, and that most false-positive alerts can be efficiently eliminated at an average slowdown cost of only 1.4%~3.6%. The net hardware cost is relatively low, so that the NUDA can readily scale increasingly complex many-core systems.