Integrating multiple cores into a processor increases the heat density significantly, which often constrains the maximum performance of such a processor. There have been many techniques using dynamic voltage and frequency scaling (DVFS) and thread migration to manipulate heat dissipation in thermally-constrained multi-core processors. However, most of them were analyzed and applied individually for optimizing the performance of the multicore processors while their computational cost for the optimization was not studied well. In this paper, we argue that a coherent organization of two techniques can maximize the performance of the multi-core processors with the least performance overheads associated with the thermal management techniques. Furthermore, we also propose an efficient method to optimize the performance of thermal-constrained multi-core processors. According to our experiment, we achieved 5% throughput improvement with negligible computation cost.