Chapter 4 - Energy Optimized Software

Abstract

This chapter focuses on energy optimized softwares. A number of techniques are available to the developer of mobile devices to insure that energy efficient software is a key driver. These techniques range from energy efficient compilation, use of standard specifications like advanced power management (APM) and advanced configuration and power interface (ACPI), and more sophisticated techniques like dynamic power management (DPM) and its extensions. It is clear that many of the complexities, either from a technology or changing standards, drive the need for more functionality realized in software. Operating system (OS) provides services such as file systems, process control, and memory management. User programs access hardware by issuing system calls through OS. An OS manages resources, including CPU time and memory allocation. DPM reduces power consumption by dynamically adjusting performance levels to the workload. A general system can be seen as a collection of interacting resources. If workload is nonstationary, some (or many) resources may be idle when the environment does not maximally load the system. The basic idea in DPM is to put underutilized or idle resources into states of operation with reduced or null performance levels that require little or no power. DPM is an independent module of the operating system concerned with active power management. DPM policy managers and applications interact with this module using a simple application program interface (API), either from the application level or the kernel level.