Abstract

this paper describes a modified form of Reference Count garbage collection which removes the need for synchronisation, and gives greater locality of store accessing. This makes it attractive for parallel machines, but does not overcome the problem of reclaiming circular structures. The solution adopted for the Flagship machine is to implement the modified Reference Count scheme, and also implement a secondary Mark-Scan collector to remove circular structures (which are rarely created in this machine). Because it is not the main method of garbage collection, the efficiency of the Mark-Scan collector is not so critical, and its overheads, for example synchronisation costs, can be more readily tolerated

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