A Trace-Driven Simulator For Palm OS Devices

Due to the high cost of producing hardware prototypes, software simulators are typically used to determine the performance of proposed systems. To accurately represent a system with a simulator, the simulator inputs need to be representative of actual system usage. Trace-driven simulators that use logs of actual usage are generally preferred by researchers and developers to other types of simulators to determine expected performance. In this paper we explain the design and results of a trace-driven simulator for Palm OS devices capable of starting in a specified state and replaying a log of inputs originally generated on a handheld. We collect the user inputs with an acceptable amount of overhead while a device is executing real applications in normal operating environments. We based our simulator on the deterministic state machine model. The model specifies that two equivalent systems that start in the same state and have the same inputs applied, follow the same execution paths. By replaying the collected inputs we are able to collect traces and performance statistics from the simulator that are representative of actual usage with minimal perturbation. Our simulator can be used to evaluate various hardware modifications to Palm OS devices such as adding a cache. At the end of this paper we present an in-depth case study analyzing the expected memory performance from adding a cache to a Palm m515 device