To cope with increasing demands for higher computational power and greater system flexibility, dynamically and partially reconfigurable logic has started to play an important role in embedded systems and systems-on-chip (SoC). However, when using traditional design methods and tools, it is difficult to estimate or analyze the performance impact of including such reconfigurable logic devices into a system design. In this work, we present a system-level framework, called Perfecto, which is able to perform rapid exploration of different reconfigurable design alternatives and to detect system performance bottlenecks. This framework is based on the popular IEEE standard system-level design language SystemC, which is supported by most EDA and ESL tools. Given an architecture model and an application model, Perfecto uses SystemC <i>transaction-level models</i> (TLMs) to simulate the system design alternatives automatically. Different hardware-software copartitioning, coscheduling, and placement algorithms can be embedded into the framework for analysis; thus, Perfecto can also be used to design the algorithms to be used in an operating system for reconfigurable systems. Applications to a simple illustration example and a network security system have shown how Perfecto helps a designer make intelligent partition decisions, optimize system performance, and evaluate task placements.