.. _legacy_mem:

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Legacy Memory Management Schemes
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Single Contiguous Allocation
===============================

.. figure:: single_contig.png
   :align: center

----------------------------

.. figure:: address_relocation.png
   :align: center

Partitioned Allocation
=================================

.. figure:: partition_mem.png
   :align: center

----------------------------

.. figure:: limit_relocation.png
   :align: center

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

.. describe:: First-fit

    Allocate the first hole that is big enough.

.. describe:: Best-fit

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

.. describe:: Worst-fit

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

Fragmentation
=================================

.. describe:: External fragmentation

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

.. describe:: Internal fragmentation

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