Advantages of Paging
Execution of any process can continue provided that the instruction it
next wants to execute, or the data location it next wants to access, is in
physical memory.
If not, the operating system must load the required memory from the
swapping (or paging) space before execution can continue.
However, the swapping space is generally on a slow device (a disk), so the
paging I/O request forces the process to be Blocked
until the required page
of memory is available.
In the interim, another process may be able to execute.
Before we consider how we can achieve this, and introduce additional
efficiency, consider what advantages are now introduced:
- More (pieces of) processes may be maintained in main physical memory
(either Ready or Running).
Most processes do not require all of their memory before they can execute:
memory may be loaded on demand.
- If the swapping space is larger than the physical memory, any single
process may now demand more memory than the amount of physical
memory installed.
This last aspect gives the technique its name: virtual memory.
CITS2002 Systems Programming, Lecture 14, p3, 12th September 2023.
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CITS2002