Paged Segmentation in Memory Management, Summaries of Data Mining

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Shared Pages

Example

Sharing of Segments

Paged Segmentation

 Divide every segment in a process into fixed size pages  Need for a page table per segment  CPU’s memory management unit must support both segmentation and paging

Paged Segmentation

1 3 2 4 logical memory 5 physical memory

Paged Segmentation

 Logical address is still <s,d>, with s used to index the segment table  Each segment table entry consist of the tuple <segment-length, page-table-base>  The logical address is legal if d < segment-length

Paged Segmentation

 Segment offset, d, is partitioned into two parts: p and d’, where p is used to index the page table associated with segment, s, and d’ is used as offset within a page

Paged Segmentation

 GE 345 processor  Logical address = 34 bits  Page size = 1 KB  s is 18 bits and d is 16 bits  Size of p and d’, largest segment size, and max. number of segments per process?

s d p d’ 18 bits 6 bits 10 bits

 Consider a process with its segment 15 having 5096 bytes. The process generates a logical address (15,3921).  Is it a legal address?  How many pages does the segment have?  What page does the logical address refer to?

 What are the value of d’ and the physical address if page number 3 (i.e., the fourth page) is in frame 12? d’ = 3921 – 31K = 849 Physical address = 121K + 849 = 13137

15 3921 3 849 s p d’ d page table for segment 15 0 1 2 3 4 12