L4oprof: A System-Wide Profiler Using Hardware PMU in L4 Environment

The recent advance of L4 microkernel technology enables building a secure embedded system with comparable performance to a traditional monolithic kernel-based system. According to the different system software architecture, the execution behavior of an application in microkernel environment differs greatly from that in traditional monolithic environment. Therefore, we need a performance profiler to improve performance of the application in microkernel environment. Currently, L4's profiling tools provides only program-level information such as the number of function calls, IPCs, context switches, etc. In this paper, we present L4oprof, a system-wide statistical profiler in L4 microkernel environment. L4oprof leverages the hardware performance counters of PMU on a CPU to enable profiling of a wide variety of hardware events such as clock cycles and cache and TLB misses. Our evaluation shows that L4oprof incurs 0~3% higher overhead than Linux OProfile. Moreover, the main cause of performance loss in L4Linux applications is shown compared with Linux applications.