LIKWID is a Linux-focused HPC performance tool suite used in production for reading and programming CPU/GPU hardware performance counters, measuring RAPL power/energy, pinning threads and MPI ranks, controlling CPU features and frequency scaling, and running synthetic microbenchmarks. It ships mature command-line tools such as likwid-perfctr, likwid-topology, likwid-pin, likwid-powermeter, likwid-bench, and likwid-mpirun, plus Marker APIs for instrumenting C, C++, Fortran, OpenMP, TBB, CUDA, and ROCm applications. The code confirms that this is a systems tool, not a data/research pipeline: its data are hardware event definitions and group files, but its primary deliverables are executables, daemons, libraries, and runtime instrumentation hooks.