A Runtime Solution for Online Contention Detection and Response

In our recent paper, Contention Aware Execution: Online Contention Detection and Response, we have made a big step forward in addressing an important and pressing problem in the field of Computer Science today. This work appears in the 2010 Proceedings of the International Symposium on Code Generation and Optimization (CGO) and was awarded the CGO 2010 Best Presentation Award at the conference.

One of the greatest challenges when using multicore processors arise when critical resources, such as the on-chip caches, are shared by multiple executing programs. If these programs simultaneously place heavy demands on shared resources, the may be forced to "take turns," and as a result, unpredictable and abrupt slowdowns may occur. This unexpected "cross-core interference" is especially problematic when considering the latency sensitive applications that are found in Google's datacenters, such as web-search. The commonly used solution is to dedicate separate machines to each application, however this leaves the processing capabilities of multicore processors underutilized. In our work, we present the Contention Aware Execution Runtime (CAER) environment that provides a lightweight runtime solution that minimizes cross-core interference, while maximizing utilization. CAER leverages the ubiquitous performance monitoring capabilities present in current state-of-the-art multicore processors to infer and respond to cross-core interference and requires no added hardware support. Our experiments show that when using our CAER system, we are able to increase the utilization of the multicore CPU by 58% on average. Meanwhile CAER brings the performance penally due to allowing co-location from 17% down to just 4% on average.