Adaptive Interrupt Coalescing for Energy Efficiency and Performance

Energy efficiency is increasingly important for future information and communication technologies (ICT). As an effort to improve energy efficiency in communications, the IEEE 802.3 Working Group approved IEEE 802.3az standard, known as Energy Efficient Ethernet (EEE) in 2010. EEE uses a Low Power Idle (LPI) mode to reduce the energy consumption of a link when no packets are being sent, but it has been shown that EEE cannot achieve good energy efficiency when small packets are sent periodically with a gap between them. To solve this problem, coalescing techniques were proposed such as packet coalescing and interrupt coalescing. EEE with either of two coalescing techniques shows better energy efficiency but its implementations typically employ a few fixed coalescing parameters and need further optimization. The paper proposes adaptive interrupt coalescing (AIC) that could improve energy efficiency and support performance as well. EEE with AIC at the sender has been implemented with the Intel 82579 network interface card (NIC) and e1000e Linux device driver. The experiments were performed at 100 M bps bandwidth to verify the feasibility of AIC. The experimental results show that energy efficiency of AIC is improved in most cases despite performance consideration and in the best case can be improved up to 37% compared to that of conventional interrupt coalescing techniques.