We present a tool for measuring network service latency times under high network load. This tool is a proof-of-concept application designed to show the viability of using programmable network data planes as a basis for both generating a high rate of network traffic and precisely measuring observed latencies. Our application uses Tofino, a network switch that is optimized for high-speed packet processing and provides a data plane architecture that has been designed to be programmed with the P4 programming language, allowing data plane designs to be mapped onto the hardware very efficiently. Our application can generate traffic that saturates Gigabit Ethernet links, and can measure observed latencies at a nanosecond-scale. Experiments we have conducted show that we can generate traffic rate patterns that closely approximate the Poisson distribution, and a practical experiment involved measuring the latency behavior of the BIND9 nameserver under various (both supported and unsupported) loads.