Energy Efficiency Through Burstiness

OS resource management policies traditionally employ buffering to “smooth out ” fluctuations in resource demand. By minimizing the length of idle periods and the level of contention during non-idle periods, such smoothing tends to maximize overall throughput and minimize the latency of individual requests. For certain important devices, however (disks, network interfaces, or even computational elements), smoothing eliminates opportunities to save energy using low-power modes. As devices with such modes proliferate, and as energy efficiency becomes an increasingly important design consideration, we argue that OS policies should be redesigned to increase burstiness for energysensitive devices. We are currently experimenting with techniques to increase the disk access pattern burstiness of the Linux operating system. Our results indicate that the deliberate creation of bursty activity can save up to 78.5 % of the energy consumed by a Hitachi DK23DA disk (in comparison with current policies), while simultaneously decreasing the negative impact of disk congestion and spin-up latency on application performance. 1