Книга: Distributed operating systems

7.4.1. Segments

7.4.1. Segments

Processes have several calls available to them for managing segments. Most important among these is the ability to create, destroy, read, and write segments. When a segment is created, the caller gets back a capability for it. This capability is used for reading and writing the segment and for all the other calls involving the segment.

When a segment is created it is given an initial size. This size may change during process execution. The segment may also be given an initial value, either from another segment or from a file.

Because segments can be read and written, it is possible to use them to construct a main memory file server. To start, the server creates a segment as large as it can. It can determine the maximum size by asking the kernel. This segment will be used as a simulated disk. The server then formats the segment as a file system, putting in whatever data structures it needs to keep track of files. After that, it is open for business, accepting requests from clients.

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