This interactive video presents the TAU Performance System to help computational scientists in tuning their codes. After describing and demonstrating how performance data is collected using TAU’s automated instrumentation, we present ways to analyze the performance data collected and how to drill down to find performance bottlenecks. TAU can internally use PAPI and LIKWID tools to generate valuable data from hardware performance counters on Intel® Xeon Phi™ (KNL) cpus in Theta that can help developers gain insight into the inner workings of the processor and memory.