Apple Inc.

Patrick W Dirks

Gursharan S Sidhu

Bill M Bruffey

Christopher R McFall

A memory manager for a virtual memory system maintains three lists of virtual addresses: those which are free to be mapped to a program, those which are currently mapped but no longer being used, and those which are being removed from a page table, i.e. unmapped. The allocation of free addresses to programs proceeds in parallel with the removal of old entries from the page table, such that new free addresses are guaranteed to be available at all times. Each time that a new address is allocated to a program, a limited number of entries in the page table are examined, to determine whether the addresses associated with those entries are no longer in use, and the entries can be removed from the page table. By the time that all of the available addresses in the free list have been allocated, the entire page table will have been examined and all addresses which are no longer in use will have had their corresponding page table entries removed, so that they are available as free addresses. As a result, a constant supply of free addresses are provided with only a limited amount of processing time at regular intervals during the operation of a computer.

Method for allocation of address space in a virtual memory system

A hierarchical filing system provides a cataloging of data stored in various locations within a memory device. An upside-down tree type structure provides a downwardly expanding cataloging structure wherein directories provide for further branchings. A branching from a directory is terminated when a file is reached. Each directory is assigned a unique directory identifier value. Then, each file or directory is coupled with the directory identifier value of its parent to provide the interconnection necessary to form the cataloging structure. The complete cataloging structure is organized in the leaf nodes of a B-Tree structure and distributed in an ascending order of the key values to provide a systematic search for a given key. Each file is capable of storing a predetermined number of location description information when data is segmented into non-contiguous segments in memory. A file extents record is used to maintain record of the further segmentation. File location information is kept in the form of file extents descriptors in the leaf nodes of the separate File Extents B-Tree. This extents information is sorted in an ascending order based on a key comprised of a unique file number of a file relative starting block location of the file extent.

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San Jose, CA, United States of America

Patrick W Dirks