Towards Concurrent Execution of Real-time and Interactive Jobs in NAND Flash Based Portable Devices

With enhanced capabilities of portable devices such as PMPs and MP3 players, the application range supported by a single portable device is extended widely. For example, not only traditional realtime programs like a video player, but also interactive applications such as web browsers and text editors are supported together. This requires the redesign of legacy portable devices that have been developed for a real-time application. In this paper, we present an effective memory management technique, called the adaptive borrowing policy, to support heterogeneous applications in portable devices based on NAND flash memory. The idea is to allow interactive jobs to use memory area reserved for a real-time task when the real-time task is inactive, which is based on the periodic characteristic of real-time tasks and uniform access time of NAND flash memory. To maximize the benefit from this policy, the borrowing size is adjusted effectively in terms of cost and benefit through periodic investigation using Belady’s life time model. Simulation studies demonstrate that the borrowing policy reduces the overall I/O time of interactive jobs by up to 64.33%, whereas providing a deadline-guaranteed service for the real-time task.