Approximate memory support for Linux early allocators in ARM architectures

Approximate computing is a new paradigm for energy efficient design, based on the idea of designing digital systems that trade off computational accuracy for energy consumption. The paradigm can be applied to different units (i.e. internal units of the CPU, floating point coprocessors, memories). Considering the memory subsystem, approximate memories are physical memories where circuit-level or architecture-level techniques are implemented in order to reduce energy at the expense of errors occurring in bit cells. Supporting approximate memories at operating system level is required for managing them efficiently and for allowing user level applications to use it directly, but its implementation is subject to specific requirements and constraints, sometimes architecture dependent. In this paper we describe the introduction of approximate memory support on ARM architectures, which are widely adopted in low power embedded systems. While Linux support for approximate memory has already been introduced for main allocators, porting it to ARM architectures required the introduction of its specific support in the Linux early allocators, that are a fundamental function of the Linux kernel startup phase, before instantiation of the main allocators.