Abstract: Softwareization of network function (NF) provides flexibility for the implementation and deployment of new network applications. However, duo to more complex program structure and running environment compared with NF hardware, NF software introduces various performance issues, such as, short-term throughput anomalies and long-tail delays, degrades user experience. Once NF performance problem occurs, it is necessary to quickly locate problematic modules and determine the cause of the problems through performance measurement. Facing to NF's complex operating environments, increasingly expanding code size, and diverse root causes of problems, coarse-grained performance measurement cannot meet the requirement of problem location and analysis. More efficient fine-grained NF performance measurement is necessary. For the two types of widely used NF performance measurement methods: sampling-based and instrumentation-based, we first prove through actual measurement analysis that, the sampling-based performance measurement method is not suitable for fine-grained NF performance measurement, and the instrumentation-based method will generate a large amount of additional measurement overhead, affecting the measurement results. To this end, we propose a function-level dynamic instrumentation method that combines dynamic library piling and function-level fast breakpoints. Compared with static instrumentation, dynamic instrumentation can execute instrumentation on demand in runtime. It is more suitable for use in the production environment. Our dynamic instrumentation method reduces the instrumentation overhead by an average of 70% compared to baseline fast breakpoints. On this basis, we design and implement the packet-level NF performance measurement method LProfile, based on lightweight probes and storage optimization. Compared with TAU, a general-purpose performance measurement tool, LProfile reduces the single-point measurement overhead by 82%.