# Andrew S. Tanenbaum (OS) Edition 4 Exercise 3 Question 12 (Page No. 255)

57 views
The amount of disk space that must be available for page storage is related to the maximum number of processes$,\: n,$ the number of bytes in the virtual address space, $v,$ and the number of bytes of $RAM,\: r$. Give an expression for the worst-case disk-space requirements. How realistic is this amount?

1 vote

The total virtual address space for all the processes $=\mathrm {nv}$

$\therefore$ amount of storage needed for pages $= \mathrm {nv}$

If an amount $\mathbf r$ is in the RAM, then the disk storage required $=\mathrm {nv-r}$

## Related questions

1
35 views
Suppose that a machine has $438-bit$ virtual addresses and $32-bit$ physical addresses. What is the main advantage of a multilevel page table over a single-level one? With a two-level page table, $16-KB$ pages, and $4-byte$ entries, how many bits should be allocated for the top-level page table field and how many for the next level page table field? Explain.
You are given the following data about a virtual memory system: The $TLB$ can hold $1024$ entries and can be accessed in $1$ clock cycle $(1\: nsec).$ A page table entry can be found in $100$ clock cycles or $100\: nsec.$ The average page replacement time is $6\: msec.$ ... by the $TLB\:\: 99\%$ of the time, and only $0.01\%$ lead to a page fault, what is the effective address-translation time?
Suppose that a machine has $48-bit$ virtual addresses and $32-bit$ physical addresses. If pages are $4\: KB$, how many entries are in the page table if it has only a single level? Explain. Suppose this same system has a $TLB$ (Translation Lookaside Buffer ... and it sequentially reads long integer elements from an array that spans thousands of pages. How effective will the $TLB$ be for this case?
A machine has a $32-bit$ address space and an $8-KB$ page. The page table is entirely in hardware, with one $32-bit$ word per entry. When a process starts, the page table is copied to the hardware from memory, at one word every $100\: nsec.$ If each process runs for $100\: msec$ (including the time to load the page table), what fraction of the $CPU$ time is devoted to loading the page tables?