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.

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

“…Our results showed that our scheme is up to 57% better than no-power-management and up to 32% better than static power-management on several embedded applications. Furthermore, we demonstrated that our compiler-directed scheme can achieve better energy reductions than a scheme that relies on the programmer and semantic information about an application (see AbouGhazaleh et al [2002] for more details). …”

“…To do so, we introduce an ISR for setting the speed [AbouGhazaleh et al 2003b] and a system call to set the application's power-management parameters in the OS. In addition, more information is stored in the process's context to support the multiprocess preemption.…”

Execution context optimization for disk energy

“…For example, hints may help ascertain the CPU demand in order to adjust voltage and frequency levels [1]. Hints have also been useful to aggressively prefetch and cache data from disk while comparing different cache policies [24,29].…”

Minimizing expected energy in real-time embedded systems

“…AbouGhazaleh et al [1] proposed a hybrid compiler-operating system intra-task DVS scheme for energy consumption of timesensitive embedded applications. Our scheme is implemented at the operating system level and assumes no access to application source codes.…”