Collaborative operating system and compiler power management for real-time applications

Abstract

Managing energy consumption has become vitally important to battery-operated portable and embedded systems. Dynamic voltage scaling (DVS) reduces the processor's dynamic power consumption quadratically at the expense of linearly decreasing the performance. When reducing energy with DVS for real-time systems, one must consider the performance penalty to ensure that deadlines can be met. In this paper, we introduce a novel collaborative approach between the compiler and the operating system (OS) to reduce energy consumption. We use the compiler to annotate an application's source code with path-dependent information called power-management hints (PMHs). This fine-grained information captures the temporal behavior of the application, which varies by executing different paths. During program execution, the OS periodically changes the processor's frequency and voltage based on the temporal information provided by the PMHs. These speed adaptation points are called power-management points (PMPs). We evaluate our scheme using three embedded applications: a video decoder, automatic target recognition, and a sub-band tuner. Our scheme shows an energy reduction of up to 57% over no power-management and up to 32% over a static power-management scheme. We compare our scheme to other schemes that solely utilize PMPs for power-management and show experimentally that our scheme achieves more energy savings. We also analyze the advantages and disadvantages of our approach relative to another compiler-directed scheme.

A Comprehensive Approach to Power Management in Embedded Systems

“…(d) Autosuspend: with accounting capabilities in hand, a power management infrastructure can deliver "autosuspend" mechanisms that automatically change the status of components that are not currently being used to energysaving modes such as standby or off ; however, suspending a component and resuming it shortly after will probably spend more energy than letting it to continue in the original mode; therefore, the heuristics used to decide which and when components should be suspended is one of the most important issues in the field and is now subject to intense research [10][11][12][13][14].…”

Controlling Energy Demand in Mobile Computing Systems

“…To illustrate this approach, we present an operating system solution that uses relatively lightweight compiler hints to convey relative progress (AbouGhazaleh et al 2006). It breaks the task into segments such that the speed and voltage can be reconsidered for each segment.…”

“…BlueFS uses ghost hints (Anand et al 2004) to address this problem of unseen requests from the disk's point of view. The problem arises when a request is directed to the currently lowest cost device, although another of the alternatives might have been preferred if it had been in an active power state at the time.…”

“…Hints have also been used in dynamic voltage scheduling (DVS), as described in Section 4.4.1 where we described the use of these hints by the OS in setting the speed and voltage during periodic interrupts called power management points (PMPs) (AbouGhazaleh et al 2006). The off-line compiler analysis annotates the program by inserting code that updates a designated memory location, the WCR.…”