Concurrent garbage collectors require write barriers to preserve consistency, but these barriers impose significant direct and indirect costs. While there has been a lot of work on optimizing write barriers, we present the first study of their elision in a concurrent collector. We show conditions under which write barriers are redundant, and describe how these conditions can be applied to both incremental update or snapshot-at-the-beginning barriers. We then evaluate the potential for write barrier elimination with a trace-based limit study, which shows that a significant percentage of write barriers are redundant. On average, 54% of incremental barriers and 83% of snapshot barriers are unnecessary.
@inproceedings{vechev2004write, title={Write barrier elision for concurrent garbage collectors}, author={Vechev, Martin T and Bacon, David F}, booktitle={Proceedings of the 4th international symposium on Memory management}, pages={13--24}, year={2004}, organization={ACM}}