4.2. Legacy Memory Management Schemes

4.2.1. Single Contiguous Allocation

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4.2.2. Partitioned Allocation

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Strategies for how to satisfy a process request of size n from a list of free holes.

First-fit

Allocate the first hole that is big enough.

Best-fit

Allocate the smallest hole that is big enough; must search entire list, unless ordered by size. Produces the smallest leftover hole.

Worst-fit

Allocate the largest hole; must also search entire list. Produces the largest leftover hole.

4.2.3. Fragmentation

External fragmentation

total memory space exists to satisfy a request, but it is not contiguous

Internal fragmentation

allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used