PPT Slide
Virtual Memory
- Combines the advantage of swapping (multiple programs space-sharing memory) and overlays (only keep the parts of a program in memory that are currently needed).
- Take the paging hardware we’ve already learned and add these rules:
- a program doesn’t have to have all it’s page table entries mapped before it runs.
- A reference to a missing page frame will cause an interrupt (a page fault), which will transfer control to the O/S.
- The page fault handler will fill in the page table entry and restart the process.
- The result is an illusion to the program of virtual memory (Figure 11.21).