Enabling zero-copy OpenMP offloading on the PULP many-core accelerator

Abstract

Many-core heterogeneous designs are nowadays widely available among embedded systems. Initiatives such as the HSA push for a model where the host processor and the accelerator(s) communicate via coherent, Unified Virtual Memory (UVM). In this paper we describe our experience in porting the OpenMP v4 programming model to a low-end, heterogeneous embedded system based on the PULP many-core accelerator featuring lightweight (software-managed) UVM support. We describe a GCC-based toolchain which enables: i) the automatic generation of host and accelerator binaries from a single, high-level, OpenMP parallel program; ii) the automatic instrumentation of the accelerator program to transparently manage UVM. This enables up to 4x faster execution compared to traditional copy-based offload mechanisms.