Provide mapping from addresses in segments to physical memory Use base and

Provide mapping from addresses in segments to

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Provide mapping from addresses in segments to physical memory Use base and limit registers to translate virtual addresses to physical addresses 1 2 Physical Memory Base register Limit register cpu < limit base + Virtual Address Physical Address
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3 1 2 Physical Memory Segmentation Allocate memory for segments Provide mapping from addresses in segments to physical memory • Problems: Segments may grow Fragmentation Large processes Swapping efficiency Base register Limit register Disk Storage 3 Paging • Motivation Mapping entire segments is too coarse granularity Mapping individual bytes is too fine granularity • Pages Divide up memory into blocks, called pages (~4KB) Each virtual page can be mapped to any physical page Each translation involves two steps: Decide which physical page holds the virtual address Decide a what offset the virtual address is inside the page The physical address is formed by gluing together the physical page number and the offset within the page
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4 Paging Page table maps virtual addresses to physical addresses Silberschatz & Peterson Paging (cont) Silberschatz & Peterson
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5 Paged Segmentation Silberschatz & Peterson Swapping What happens if cumulative sizes of segments exceeds virtual memory?
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