Energy efficiency has become a key concern in modern computing. Major processor vendors now offer single-ISA heterogeneous processors that combine powerful and energy-efficient cores, such as Arm's big.LITTLE CPUs, Apple's M-series chips, and Intel P/E systems. However, today's OS schedulers, relying on simple cost-based thread allocation strategies, fail to fully exploit their potential.This paper presents HARP, a Linux-integrated resource-management framework for heterogeneous processors. HARP leverages application behavior through online monitoring or application descriptions and introduces a lightweight interface for two-way communication between applications and the resource manager. Through this interface, HARP learns application characteristics to guide allocation decisions, which are then relayed back to the applications so they can adapt accordingly. HARP supports various programming models, from OpenMP and Intel TBB to custom models with adaptivity features, significantly improving performance and energy efficiency, particularly in multi-application scenarios. On two representative heterogeneous systems, HARP reduces the average execution time by 12 % and the energy consumption by 28 % compared to existing methods. Overall, HARP marks a crucial step toward energy-efficient computing across diverse architectures.