Reducing Power Consumption for Mobile Platforms via Adaptive Traffic Coalescing

Battery life remains to be a critical competitive metric for today's mobile platforms that offer ubiquitous connectivity through their wireless communication interfaces. With most usage models being driven by always-on communication activities, e.g, Internet video streaming, web browsing, etc., it is imperative to understand the impact of network activities on the overall platform power, and optimize power consumption for such activities. As shown by our investigation, various real-world network-driven workloads exhibit bursty and random behavior, which motivates our work on regulating and coalescing incoming packets to reduce platform wake events. To understand the performance impact of packet coalescing, we conduct an extensive investigation to study how coalescing may affect the throughput and user experience. Armed with the deep understandings, we propose, implement and evaluate an Adaptive Traffic Coalescing (ATC) scheme that monitors the incoming traffic at the Network Interface Card (NIC), and adaptively coalesces the packets for a limited duration in the NIC buffer, thus requiring no network or eco-system support. The proposed ATC scheme effectively reduces platform wake events, and enables the platform to enter and stay in the low-power state longer for energy efficiency. We have implemented the scheme in commercial wireless NICs. Using various mobile platforms, we evaluate the power savings and performance impact of the proposed ATC scheme. Experiments show that ATC achieves significant power saving for major platform components, around 20% for real-world Internet workloads, without impacting performance and user experience.