[Research Paper] POI: Skew-Aware Parallel Race Detection

Abstract

Multithreaded programs are prone to dataraces. Dataraces are known to be hard to detect and reproduce by manual effort, although they often have detrimental effects on program reliability. Automated techniques are thus demanded for detecting dataraces efficiently and precisely. There have been proposed a lot of datarace detectors so far, among which dynamic ones are promising because of their precision. However, existing dynamic race detectors incur high race-checking overheads. Even a state-of-the-art dynamic race detector, called Parallel FastTrack, fails to efficiently detect races under certain conditions, despite its attempt to parallelize race detection for efficiency. In this paper, we propose an efficient and precise parallel race detector. For our proposal, we first experimentally reveal that the load-distribution policy of Parallel FastTrack tends to skew race-checking loads to a few detection threads. We then present a simple but effective technique, called POI, for balancing race-checking loads among detection threads. POI takes race-checking loads of each detection thread into account and reduces the load skew by making each detection thread manage almost the same number of memory addresses to be checked. Experiments on several real multithreaded data-processing applications show that POI succeeded in reducing, on average, about 37% of race detection overheads, which the load-distribution policy of Parallel FastTrack would impose.