  We present a family of policies that, integrated within a runtime task
scheduler (Nanox), pursue the goal of improving the energy efficiency of
task-parallel executions with no intervention from the programmer. The proposed
policies tackle the problem by modifying the core operating frequency via DVFS
mechanisms, or by enabling/disabling the mapping of tasks to specific cores at
selected execution points, depending on the internal status of the scheduler.
Experimental results on an asymmetric SoC (Exynos 5422) and for a specific
operation (Cholesky factorization) reveal gains up to 29% in terms of energy
efficiency and considerable reductions in average power.
