WSMeter

Abstract

Evaluating the comprehensive performance of a warehouse-scale computer (WSC) has been a long-standing challenge. Traditional load-testing benchmarks become ineffective because they cannot accurately reproduce the behavior of thousands of distinct jobs co-located on a WSC. We therefore evaluate WSCs using actual job behaviors in live production environments. From our experience of developing multiple generations of WSCs, we identify two major challenges of this approach: 1) the lack of a holistic metric that incorporates thousands of jobs and summarizes the performance, and 2) the high costs and risks of conducting an evaluation in a live environment. To address these challenges, we propose WSMeter, a cost-effective methodology to accurately evaluate a WSC's performance using a live production environment. We first define a new metric which accurately represents a WSC's overall performance, taking a wide variety of unevenly distributed jobs into account. We then propose a model to statistically embrace the performance variance inherent in WSCs, to conduct an evaluation with minimal costs and risks. We present three real-world use cases to prove the effectiveness of WSMeter. In the first two cases, WSMeter accurately discerns 7% and 1% performance improvements from WSC upgrades using only 0.9% and 6.6% of the machines in the WSCs, respectively. We emphasize that naive statistical comparisons incur much higher evaluation costs (> 4 times) and sometimes even fail to distinguish subtle differences. The third case shows that a cloud customer hosting two services on our WSC quantifies the performance benefits of software optimization (+9.3%) with minimal overheads (2.3% of the service capacity).