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Discussion/Midterm Question

Discussion/Midterm Question. Assume a system with a two level page table. The virtual memory address space is 32 bits and the physical memory address space is 16 bits. . Factors in determining size of page. Page table fits on one page Equal sized L1 and L2 page tables

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Discussion/Midterm Question

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  1. Discussion/Midterm Question

  2. Assume a system with a two level page table. The virtual memory address space is 32 bits and the physical memory address space is 16 bits.

  3. Factors in determining size of page • Page table fits on one page • Equal sized L1 and L2 page tables • Size of a page table entry • size of physical memory (16 bit address space) • bookkeeping bits

  4. Fitting a page table on one page (size of page) (size of page table) ≥ • Size of page • # of PTE • Size of PTE (size of page table) = (# of PTEs) * (size of PTE) • (2offset) • (2(32-offset)/2) (16 bits - offset + bookkeeping ≈ 1-4 bytes) 2offset ≥ 2(32-offset)/2 (assuming 1 byte PTE) offset ≥ 10.667

  5. Fitting a page table on one page (size of page) (size of page table) ≥ • Size of page • # of PTE • Size of PTE (size of page table) = (# of PTEs) * (size of PTE) • (2offset) • (2(32-offset)/2) (16 bits - offset + bookkeeping ≈ 1-4 bytes) 2offset ≥ 2(32-offset)/2*22 (assuming 4 byte PTE) offset ≥ 12 12 bit offset works under either assumption

  6. Solutions • Offset = 12 • 4KB pages • VPN1 = VPN2 = 10 • 210 entries per page table

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