Inverted Page Table
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With very large address spaces,
page tables can become too large.
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The inverted page table limits the
page table size.
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The inverted page table has one
entry for each physical frame.
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TLB + Hashing improves the effective
memory access time
Example:
Inverted page table of RS/6000
Segmentation
Pure Segmentation:
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Supports user's view of memory as
collection of segments
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Segments such as function bodies,
data structures, main ..
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Address: | #seg | offset
|
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Segment table maps #seg to physical
memory frame
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Segment table limit register
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Segment table base register
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Sharing of segments
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External Fragmentation
Page every segment:
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Eliminates external fragmentation
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Every segment is composed of multiple
pages
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'offset' in pure segmentation now
includes a page number
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Address: | #seg | #page
| offset |
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Now you have a segment table and
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A page table for every segment entry
in the segment table
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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
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Address: | #page | offset
| #page | offset |
Example: MULTICS segmentation
with paging