US 5,390,318 A · Managing the fetching and replacement of cache entries associated with a file system

Abstract

Information needed by application programs from a secondary storage is cached in a cache memory which is organized in multiple levels, each level having multiple entries, the entries of each level receiving information of a predetermined category, each entry being accessible independently. Links are defined between entries of one level of the cache memory and entries at another level of the cache memory, the links corresponding to information relationships specified by a user of information stored in the secondary storage. In response to a request to a file system from an application for needed information, the needed information is fetched into the cache, and in connection with fetching the needed information, other information is prefetched from the system of files which is not immediately needed. Quotas are established on information which may be fetched from a secondary storage into the cache, the quotas being applicable to file contents within a file and to the number of files within a directory. Upon a request from an application program to open a file, an entry is created in a cache corresponding to the file, the entry including file header information. The file header information is retained in the cache so long as the file remains open, whether or not any file contents of the file remain in cache. The entries of three level of the cache respectively receive directory information, file header information, and file contents information.

Claims62

Dependent claims

A method for managing the use and re-use of entries of a cache, said entries containing data retrieved from a mass storage into said cache to be thereafter available for use by a computer system, comprising the computer system

grouping entries;
assigning each entry a priority for storage relative to other entries of the same group;
identifying at least a first entry and a second entry belonging to different respective said groups which are related in a system of files in said mass storage;
and
selecting one of said entries of said cache for re-use according to the priority for storage assigned to said entry and the priority for storage assigned to identified related entries.

2 more elements

A method for caching information retrieved by application programs from files organized in a file system in mass storage, comprising

organizing a cache in at least two levels having multiple cache entries, including an upper level comprising directory entries storing directory file information and representing directories in said file system, and a lower level comprising file header entries storing file header information and representing files in said file system,
identifying file header and directory entries related such that the identified directory entry represents the directory containing the file represented by the identified file header entry, and storing pointers in the cache linking the related entries,
assigning each entry a priority for storage relative to the other entries in the same level, and
managing use and re-use of said cache entries according to the priority for storage assigned to said entries.

1 more element

Dependencies are inferred from the claim text.

Managing the fetching and replacement of cache entries associated with a file system

Life of this patent

Managing the fetching and replacement of cache entries associated with a file system

Life of this patent

Abstract

Claims62