Task support was introduced into OpenMP to address irregular parallelism in shared memory architectures. Creating tasks that are extremely fine granular in applications, however, impedes performance. In this paper, a methodology for analyzing the performance of task-based OpenMP programs and its implementation in Periscope is presented. The paper unveils and concentrates on the newly formulated high-level performance properties that formalize typical performance bottlenecks of task-based programs. In addition, the paper reports on the experimental results which were accomplished for the codes of the Barcelona OpenMP Tasks Suite (BOTS) using Periscope in the SuperMUC supercomputing machine at Garching, Germany.