Power Sandbox: Power Awareness Redefined

Many apps benefit from knowing their power consumption and adapting their behaviors on the fly. To offer apps power knowledge at run time, an OS often meters system power and divides it among apps. Since the impacts of concurrent apps on system power are entangled, this approach not only makes it difficult to reason about power but also results in power side channels, a serious vulnerability. To this end, we introduce a new OS principal called power sandbox, which enables one app to observe the fine-grained power consumption of itself running in its vertical slice of the hardware/software stack. The observed power is insulated from the impacts of other apps. Our contribution is a set of lightweight kernel extensions that simultaneously i) enforce the power sandbox boundaries and ii) confine entailed performance loss to the sandboxed apps. Our experiences on two embedded platforms show that power sandboxes simplify reasoning about power, maintain fairness among apps, and minimize power side channels, thus facilitating construction of power-aware apps.