Virtual memory: page management
Optimizing page placement: reduces page faults
Map any virtual page to any physical page (fully-associative)
Operating system can use sophisticated algorithms and data structures
to keep track of page usage
Problem with full-associative mapping: need to search entire set of pages
Full searching is impractical: use page table
Page table stored in memory
Contains the physical page number for every virtual page number
Each program has own page table
To access page table easily, 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