# Recent questions tagged page-replacement

1 vote
1
Non-contiguous memory allocation splits program into blocks of memory called ________ that can be loaded in non-adjacent holes in main memory. Pages Frames Partition Segments
2
Determine the number of page faults when references to pages occur in the following order: $1,2,4,5,2,1,2,4$. Assume that the main memory can accommodate $3$ pages and the main memory already has the pages $1$ and $2$, with page $1$ having been brought earlier than page $2$.(LRU algorithm is used). $3$ $5$ $4$ None of these.
3
Working set$(t,k)$ at an instant of time, $t$,is The set of $k$ future references that the operating system will make The set of future references that the operating system will make in the next $'k'$ time units The set of $k$ references with high frequency The set of pages that have been referenced in the last $k$ time units
4
In which one of the following pages replacement policies, Belady's anomaly may occur? FIFO LRU Optimal MRU
5
The total number of page faults for the reference string $1,2,3,4,5,6,7,8,9,10$ using FIFO page replacement policy for a process, if $3$ frames are allocated to it are $9$ $10$ $8$ $11$
6
Consider the following page reference string. $1\ 2\ 3\ 4\ 2\ 1\ 5\ 6\ 2\ 1\ 2\ 3\ 7\ 6\ 3\ 2\ 1\ 2\ 3\ 6\$ What are the minimum number of frames required to get a single page fault for the above sequence assuming LRU replacement strategy? $7$ $4$ $6$ $5$
7
Write a program that will demonstrate the difference between using a local page replacement policy and a global one for the simple case of two processes. You will need a routine that can generate a page reference string based on a statistical model. This model has $N$ ... a global policy instead of a local one. Also, contrast the per-process page fault rate with that of the local policy approach.
8
One of the first timesharing machines, the $DEC\: PDP-1,$ had a (core) memory of $4K\: 18-bit$ ... drum. The drum could start writing (or reading) at any word, rather than only at word $0.$ Why do you suppose this drum was chosen?
1 vote
9
Consider the following two-dimensional array: int X[64][64]; Suppose that a system has four page frames and each frame is $128$ words (an integer occupies one word). Programs that manipulate the $X$ array fit into exactly one page and always occupy page $0.$ The data are swapped in and out of the other three frames ... B for (int i = 0; i < 64; i++) for (int j = 0; j < 64; j++) X[i][j] = 0;
10
Suppose that two processes $A$ and $B$ share a page that is not in memory. If process $A$ faults on the shared page, the page table entry for process $A$ must be updated once the page is read into memory. Under what conditions should the page table update ... of process $A's$ page fault will bring the shared page into memory? Explain. What is the potential cost of delaying the page table update?
11
A computer has four page frames. The time of loading, time of last access, and the $R$ and $M$ bits for each page are as shown below (the times are in clock ticks): Which page will NRU replace? Which page will FIFO replace? Which page will LRU replace? Which page will second chance replace?
1 vote
12
How long does it take to load a $64-KB$ program from a disk whose average seek time is $5\: msec,$ whose rotation time is $5 msec,$ and whose tracks hold $1\: MB$ for a $2-KB$ page size? for a $4-KB$ page size? The pages are spread randomly around the disk and the number of cylinders is so large that the chance of two pages being on the same cylinder is negligible.
13
A student has claimed that ‘‘in the abstract, the basic page replacement algorithms (FIFO, LRU, optimal) are identical except for the attribute used for selecting the page to be replaced.’’ What is that attribute for the FIFO algorithm? LRU algorithm? Optimal algorithm? Give the generic algorithm for these page replacement algorithms.
14
Suppose that the $\text{WSClock}$ page replacement algorithm uses a $\tau$ of two ticks, and the system state is the following: where the three flag bits $V, R,$ and $M$ ... to a read request to page $4.$ Show the contents of the new table entries. Explain. (You can omit entries that are unchanged.)
15
In the $\text{WSClock}$ algorithm of Fig. $3-20(c),$ the hand points to a page with $R = 0.$ If $\tau = 400,$ will this page be removed? What about if $\tau = 1000?$
16
Give a simple example of a page reference sequence where the first page selected for replacement will be different for the clock and $LRU$ page replacement algorithms. Assume that a process is allocated $3=\text{three}$ frames, and the reference string contains page numbers from the set $0, 1, 2, 3.$
17
A small computer on a smart card has four page frames. At the first clock tick, the $R$ bits are $0111\:\: ($page $0$ is $0,$ the rest are $1).$ At subsequent clock ticks, the values are $1011, 1010, 1101, 0010, 1010, 1100,$ and $0001.$ If the aging algorithm is used with an $8-bit$ counter, give the values of the four counters after the last tick.
18
Consider the page sequence of Fig. $3-15(b)$. Suppose that the $R$ bits for the pages $B$ through $A$ are $11011011,$ respectively. Which page will second chance remove?
19
If $FIFO$ page replacement is used with four page frames and eight pages, how many page faults will occur with the reference string $0172327103$ if the four frames are initially empty? Now repeat this problem for$LRU.$
20
Suppose that the virtual page reference stream contains repetitions of long sequences of page references followed occasionally by a random page reference. For example, the sequence$: 0, 1, \dots, 511, 431, 0, 1, \dots , 511, 332, 0, 1, \dots$ consists of ... $500$ page frames, describe a page replacement approach that would perform much better than the $\text{LRU, FIFO, or clock}$ algorithms.
21
A student in a compiler design course proposes to the professor a project of writing a compiler that will produce a list of page references that can be used to implement the optimal page replacement algorithm. Is this possible? Why or why not? Is there anything that could be done to improve paging efficiency at run time?
1 vote
22
Consider that a process has been allocated $3$ frames and has a sequence of page referencing as $1, 2, 1, 3, 7, 4, 5, 6, 3, 1$. What shall be the difference in page faults for the above string using the algorithms of LRU and optimal page replacement for referencing the string? $2$ $0$ $1$ $3$
23
24
Can anyone explain me the working of NRU & SECOND CHANCE REPLACEMENT ALGORITHM.
25
Assume there are 5 frames and consider the following reference string find the number of page faults using NRU page replacement algorithm. 3,2,3, 0,8,4,2,5,0,9,8,3,2
26
What is the reason for Belady’s Anomaly,I am aware that it is not a stack based algorithm and for a certain set of pages it shows this anomaly where the increase in page frame increases the page fault rate.