Hardware Support for Concurrent Detection of Multiple Concurrency Bugs on Fused CPU-GPU Architectures

Abstract

Detecting concurrency bugs, such as data race, atomicity violation and order violation, is a cumbersome task for programmers. This situation is further being exacerbated due to the increasing number of cores in a single machine and the prevalence of threaded programming models. Unfortunately, many existing software-based approaches usually incur high runtime overhead or accuracy loss, while most hardware-based proposals usually focus on a specific type of bugs and thus are inflexible to detect a variety of concurrency bugs. In this paper, we propose Hydra, an approach that leverages massive parallelism and programmability of fused CPU-GPU architectures to simultaneously detect multiple concurrency bugs in threaded software, including data race, atomicity violation and order violation. Hydra extends contemporary fused CPU and GPU by introducing two modules: 1) a trace collecting module (TCM) that instruments and collects program behavior on CPU; 2) a trace preprocessing module (TPM) that processes and then transfers the traces to GPU for bug detection. Furthermore, Hydra exploits three optimizations to improve speed and accuracy, which includes: 1). using the bloom filter to filter out unnecessary traces; 2). avoiding eviction of shared traces; 3). comparing only last-write traces for shared data with the happens-before relation. Hydra incurs small hardware complexity and requires no changes to internal critical-path processor components such as cache and its coherence protocol, and is with about 1.1 percent hardware overhead under a 32-core configuration. Experimental results show that Hydra only introduces about 0.18 percent overhead on average for detecting one type of bugs and 0.46 percent overhead for simultaneously detecting multiple bugs, yet with the similar detectability of a heavyweight software bug detector (e.g., Helgrind).