Tech Report: A Virtualized Scratchpad-Based Architecture for Real-time Event-Triggered Applications

Systems-on-a-Chip (SoC) devices integrating hard processing cores with programmable logic (PL) are becoming increasingly available. While these platforms have been originally designed for high performance computing applications, their rich feature set can be exploited to efficiently implement mixed criticality domains serving both critical hard real-time tasks, as well as soft real-time tasks. In this paper, we take a deep look at COTS-based heterogeneous SoCs that incorporates PL and a multicore processor. We show how one can tailor these processors to support a mixed/full criticality system, where cores are strictly isolated to avoid contention on shared resources such as Last-Level Cache (LLC) and main memory. In order to avoid conflicts in LLC, we propose the use of cache coloring, implemented in the Jailhouse hypervisor. In addition, we employ ScratchPad Memory (SPM) inside the PL to support a multi-phase execution model for realtime tasks that avoids conflicts in shared memory. We provide a full-stack, working implementation on a latest-generation SoC platform, and show results based on both a set of data intensive tasks, as well as a complete case study based on an anomaly detection application for an autonomous vehicle.