Leakage aware hardware and stochastic power scheduling for smart mobile devices

Abstract

A core requirement of effective and efficient management of energy is a good understanding of where and how the energy is used; how much of the system’s energy is consumed by which parts of the system and under what circumstances.
In this work, a Smartphone is developed, hereafter referred to as the XLP, from the ground up with modular architecture where each module is supplied through an active switch matrix which takes the module to the lowest possible energy state. The basic notion of this architecture is achieving near zero-leakage power for modules which are not being used. This significantly reduces the idle power consumption which accounts for more than 60% of the average power consumed in smart phones [1, 2]. In addition to this approach on the hardware architecture, a stochastic dynamic power scheduling and on-demand power and clock gating policies are developed. A number of possible policies are presented and, under given conditions, one of them is proved to be optimal using the energy response time product (ERP) metrics.
The XLP is compared with three commercial smart phones: Openmoko Freerunner, HTC Dream and Google’s Nexus One on similar tests and usage scenarios. The comparison is on performance versus power consumption. The XLP is proved to have the lowest power consumption (up to 3x lower) on competitive performance levels.

Keywords: Zero-leakage; on-demand power gating; active switch matrix; ERP; profile-driven; XLP.