Garbage collection in an object cache

Abstract

A method for garbage collection in a cache of information objects is provided. A non-volatile storage device is segmented into storage areas called pools. Each pool has a pool header and a plurality of arenas. Each arena stores one or more fragments of an object. Header information for each arena is stored in the pool header in which that arena is stored. Each fragment comprises a fragment header and fragment data. The garbage collection periodically selects a pool that is storing an amount of data greater than a minimum storage value or high water mark. Each arena in the pool is examined and selected for garbage collection according to selection criteria. Each fragment within a selected arena is examined based upon a second set of selection criteria that determine whether the fragment is retained or deleted. If the fragment is deleted, all other fragments in the storage device that relate to that fragment's object are also deleted. When a fragment arena is retained, it is moved into contiguous storage in another available arena. A computer program product, computer apparatus, and data signal embodied in a carrier wave, configured to carry out the steps of the method, are also disclosed.