• With very large address spaces, page tables can become too large.
• The inverted page table limits the page table size.
• The inverted page table has one entry for each physical frame.
• TLB + Hashing improves the effective memory access time

Segmentation

Pure Segmentation:

• Supports user's view of memory as collection of segments
• Segments such as function bodies, data structures, main ..
• Address:  | #seg  | offset |
• Segment table maps #seg to physical memory frame
• Segment table limit register
• Segment table base register
• Sharing of segments
• External Fragmentation

• Eliminates external fragmentation
• Every segment is composed of multiple pages
• 'offset' in pure segmentation now includes a page number
• Address:  | #seg  | #page | offset |
• Now you have a segment table and
• A page table for every segment entry in the segment table
• For large address spaces, the segment table could be very large

Page the segment table itself:

• If the segment table is very large, it can be paged
• The segment table is now composed of many pages
• Address:  | #page  | offset | #page | offset |