Importance

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Abstract

A system for mostly concurrent compaction in a garbage collection system is disclosed. Objects that have been allocated to a program are relocated by first identifying those variables pointing to a selected set of objects that are in use within a subset of memory. As these pointers are identified, they are added to a data structure. The selection of the objects, identification of the pointers, and addition of the pointers to the data structure may all be performed concurrently with execution of the program. At the same time, a write barrier marks as 'dirty' those memory regions in which one or more pointers are modified by the program. A number of locations outside the subset of memory are reserved to be used to store the selected objects. Execution of the program is then suspended. The memory regions marked as 'dirty' are examined to identify any further variables pointing to the selected objects. Any such identified variables are added to the data structure. Those variables contained in the data structure that continue to point to the selected objects are modified to point to corresponding locations outside of the subset of memory. The selected set of objects is then copied to the locations outside of the subset of memory, the subset of memory is returned to the free list, and the program is restarted.

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First Claim