The Research On Memory Management System And Its Implementation In Extensible OS

With the development of science and technology, applications in recent scopes bring forward much new requirement. Operating systems at present can support general applications to certain extends, although they can not guarantee some special applications, such as multimedia based on network, large-scale DBMS, distributed computing and so on. Under this background, extensible operating system is evolved and in progress.Firstly, this paper introduces the history of extensible OS, and then analyses three key issues in memory management under extensible OS, which are performance, extensibility and integrity. And we explore the models of extensibility and safety in different categories.Secondly, based on the study, we adopt a orthogonal model of memory management subsystem under extensible OS. The model is comprised of two layers, which are application-dependent and application-independent. According to the functions, the layer of application-dependent handles with the high-level abstracts; the layer of application-independent supplies the machine-dependent interfaces of resources and servers. In the model, we use an upcall mechanism based on event, which advances the extensibility and performance of the system; use a protection mechanism based on capability, which guarantees the secure multiplex of resources in the system.Thirdly, we design and implement an executable memory management subsystem that supports self-paging. In this subsystem, we present a bran-new architecture and scheme of design. To support extensibility, we abstract the physical address space and the virtual address space in a different way; at the same time we expose these abstracts. To save the cost of space and time, we implement a kind of lazy management mechanism of application-cache on virtual address space. To implement self-paging, a new strategy is given that caches physical pages in application level and kernel level, which improves the performance of the subsystem. Because of changing the structure of UVM, we design the physical mapping and the management of kernel address space over again.Lastly, we analyze the subsystem in aspect of performance, extensibility and integrity. We also take simple tests about it.