Hardware-assisted software event tracing

Event tracing is a reliable and a low-intrusiveness method to debug and optimize systems and processes. Low overhead is particularly important in embedded systems where resources and energy consumption is critical. The most advanced tracing infrastructures achieve a very low footprint on the traced software, bringing each tracepoint overhead to less than a microsecond. To reduce this still non-negligible impact, the use of dedicated hardware resources is promising. In this paper, we propose complementary methods for tracing that rely on hardware modules to assist software tracing. We designed solutions to take advantage of CoreSight STM, CoreSight ETM, and Intel BTS, which are present on most newer ARM-based systems-on-chip and Intel x86 processors. Our results show that the time overhead for tracing can be reduced by up to 10 times when assisted by hardware, as compared to software tracing with LTTng, a high-performance tracer for Linux. We also propose a modification to the Perf tool to speed BTS execution tracing up to 65%.

Mots clés

ARM CoreSight; debugging; dedicated hardware; event tracing; Intel BTS; LTTng