Virtual memory: page management

Optimizing page placement: reduces page faults

Fully-associative: map any virtual page to any physical page

Operating system can afford to use sophisticated algorithms and data structures

to keep track of page usage

Problem with fully-associative mapping: need to search entire set of pages

Full searching is impractical: use page table

Stored in memory

Contains the physical page number for every virtual page number

Each program has its own page table

To assist accessing page table, hardware has page table register

Points to start of page table

Valid bit is used as in cache

Note that page table is indexed by virtual page number: no tags needed

Fig 7.22