On-the-fly load data value tracing in multicores

Abstract

Software testing and debugging of modern multicore-based embedded systems is a challenging proposition because of growing hardware and software complexity, increased integration, and tightening time-to-market. To find more bugs faster, software developers of real-time embedded systems increasingly rely on on-chip trace and debug resources, including hefty on-chip buffers and wide trace ports. However, these resources often offer limited visibility of the system, increase the system cost, and do not scale well with a growing number of cores. This paper introduces mlvCFiat, a hardware/software mechanism for capturing and filtering load data value traces in multicores. It relies on first-access tracking in data caches and equivalent modules in the software debugger to significantly reduce the number of trace events streamed out of the target platform. Our experimental evaluation explores the effectiveness of the proposed technique as a function of cache sizes, encoding mechanism, and the number of cores. The results show that mlvCFiat significantly reduces the total trace port bandwidth. The improvements relative to the existing Nexus-like load data value tracing range from 15 to 33 times for a single core and from 14 to 20 times for an octa core.