5.2. Legacy Memory Management Schemes¶

5.2.1. Single Contiguous Allocation¶

../_images/single_contig.png

../_images/address_relocation.png

5.2.2. Partitioned Allocation¶

../_images/partition_mem.png

../_images/limit_relocation.png

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.

5.2.3. 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