Improving SoC Insight Through On-Chip Diagnosis.

To find the cause of a functional or non-functional defect (bug) in software running on a multi-processor System-on-Chip (MPSoC), developers need insight into the chip. Tracing systems provide this insight non-intrusively, at the cost of high off-chip bandwidth requirements. This I/O bottleneck limits the observability, a problem becoming more severe as more functionality is integrated on-chip. In this paper, we present the diagnosis system, a replacement for todayu0027s tracing systems. Its main idea is to partially execute the analysis of observation data on the chip; in consequence, more information and less data is sent to the attached host PC. In the diagnosis system, the data analysis is performed by the diagnosis application. Its input are events, which are generated by observation hardware at interesting points in the program execution (like a function call). Its outputs are events with higher information density. The event transformation is modeled as dataflow application. For execution, it is mapped in part to dedicated and distributed on-chip components, and in part to the host PC; the off-chip boundary is transparent to the developer of the diagnosis application. We evaluate the concept using an FPGA and software based prototype on two use cases: finding a functional software bug, and creating a lock contention profile. Our results show that on-chip analysis of software observations is feasible and can significantly lower the off-chip bandwidth requirements, while providing insight into the software execution in line with existing tracing solutions.