Summary

• In order to effectively manage virtual memory the operating system adopts the following memory management strategies:

  Demand Paging

  only pages that a process demands are brought into memory,

  Swapping

  Pages that have been modified are swapped out to a swap file when the system starts to run out of memory,

  Discarding Pages

  Pages that can easily be re-read from an image or data file are discarded when the system starts to run out of memory,

  Shared Libraries

  Useful code is put into shared libraries so that it is not duplicated.

• There has to be a close interaction between the operating system and the CPU in order to correctly utilize virtual memory. Linux runs on a number of very different hardware platforms and so it must separate out the hardware specific code and data structures from the operating specific code and data structures.
• The operating system runs from physical memory.