(A) memory management system for PDA

Abstract

Rapid advances in hardware technology will bring about personal digital assistants(PDAs) as small as wallet. PDAs have different storage organization from conventional portable computers since PDAs must be small, light-weight, reliable, and low-power consumed. This new organization have many multimplications for operating systems. PDAs will use DRAM as primary memory and flash memory as secondary storage. All storages offer uniform and random access read times. We designed "execute-in-place" features such that the kernel executes process on flash memory directly. That reduces copy overhead and page faults. For making simple and efficient memory manager, we designed 32-bit single virtual address space system. That makes page table management simple, reduces context switching overhead and makes sharing between processes easy. We evaluated performance improvement by means of simulation when we used "execute-in-place" feature. The page faults reduced by about 30%. Besides, we concluded that we could use clock page replacement algorithm when there were no page faults about code segment.