Data processing memory space allocation and deallocation arrange

Details Data processing memory space allocation and deallocation arrange Data processing memory space allocation and deallocation arrange

1976-10-08

1978-10-17

Shaw, Gareth D.

Boots, shoes, and leggings

364900, G06F 1100

Patent

active

041212860

ABSTRACT:
When a storage block is returned to the store allocator the master capability table (MCT) entry defining the block must also be deallocated. However, an arbitrary number of capability pointers to that block may still exist in the live system and these must be cancelled before the MCT entry is re-used. The cancellation operation ideally requires a system freeze which cannot be contemplated in a real-time environment. Accordingly each MCT entry includes a "garbage" bit and "visited" bit and the garbage bit is set each time a "load capability register" instruction is performed and a garbage collection process is used to detect blocks which can be freed. The garbage collection process involves (i) re-setting the garbage and visited bits of all MCT entries (ii) testing each MCT entry (iii) setting each visited bit for each tested MCT entry having its garbage bit set and (iv) setting the garbage bit in each MCT entry listed in a segment storing a list of segments and (v) marking for release only those segments whose garbage bits are in the second state when all visited bits of the segments storing list of segments have been set.

REFERENCES:
patent: 3778776 (1973-12-01), Hakozaki
patent: 3902163 (1975-08-01), Amdahl et al.
patent: 3949379 (1976-04-01), Ball
patent: 4024507 (1977-05-01), Berkling et al.

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