Deck 18: Understanding Virtual Memory and Page Replacement Algorithms

Question 1

Virtual memory allows___________

A)execution of a process that may not be completely in memory
B)a program to be smaller than the physical memory
C)a program to be larger than the secondary storage
D)execution of a process without being in physical memory

Answer 1

execution of a process that may not be completely in memory

Question 2

A process is thrashing if___________

A)it is spending more time paging than executing
B)it is spending less time paging than executing
C)page fault occurs
D)swapping can not take place

Answer 2

it is spending more time paging than executing

Question 3

The ability to execute a program that is only partially in memory has benefits like

A)the amount of physical memory cannot put a constraint on the program
B)programs for an extremely large virtual space can be created
C)throughput increases
D)all of the mentioned

Answer 3

all of the mentioned

Question 4

Virtual memory is normally implemented by___________  

A)demand paging
B)buses
C)virtualization
D)all of the mentioned

Question 5

Segment replacement algorithms are more complex than page replacement algorithms because___________

A)segments are better than pages
B)pages are better than segments
C)segments have variable sizes
D)segments have fixed sizes

Question 6

A swapper manipulates___________         whereas the pager is concerned with individual___________of a process.

A)the entire process, parts
B)all the pages of a process, segments
C)the entire process, pages
D)none of the mentioned

Question 7

Using a pager___________

A)increases the swap time
B)decreases the swap time
C)decreases the swap time & amount of physical memory needed
D)increases the amount of physical memory needed

Question 8

The valid - invalid bit, in this case, when valid indicates?

A)the page is not legal
B)the page is illegal
C)the page is in memory
D)the page is not in memory

Question 9

A page fault occurs when?

A)a page gives inconsistent data
B)a page cannot be accessed due to its absence from memory
C)a page is invisible
D)all of the mentioned

Question 10

When a page fault occurs, the state of the interrupted process is___________

A)disrupted
B)invalid
C)saved
D)none of the mentioned

Question 11

When a process begins execution with no pages in memory?

A)process execution becomes impossible
B)a page fault occurs for every page brought into memory
C)process causes system crash
D)none of the mentioned

Question 12

If the memory access time is denoted by 'ma' and 'p' is the probability of a page fault (0 <= p <= 1). Then the effective access time for a demand paged memory is

A)p x ma + (1-p) x page fault time
B)ma + page fault time
C)(1-p) x ma + p x page fault time
D)none of the mentioned

Question 13

When the page fault rate is low

A)the turnaround time increases
B)the effective access time increases
C)the effective access time decreases
D)turnaround time & effective access time increases

Question 14

Locality of reference implies that the page reference being made by a process

A)will always be to the page used in the previous page reference
B)is likely to be one of the pages used in the last few page references
C)will always be one of the pages existing in memory
D)will always lead to page faults

Question 15

Which of the following page replacement algorithms suffers from Belady's Anomaly?

A)optimal replacement
B)lru
C)fifo
D)both optimal replacement and fifo

Question 16

A memory page containing a heavily used variable that was initialized very early and is in constant use is removed, then the page replacement algorithm used is___________

A)lru
B)lfu
C)fifo
D)none of the mentioned

Question 17

Users___________that their processes are running on a paged system.

A)are aware
B)are unaware
C)may unaware
D)none of the mentioned

Question 18

If no frames are free,___________page transfer(s) is/are required.

A)one
B)two
C)three
D)four

Question 19

A FIFO replacement algorithm associates with each page the___________

A)time it was brought into memory
B)size of the page in memory
C)page after and before it
D)all of the mentioned

Question 20

What is the Optimal page - replacement algorithm?

A)replace the page that has not been used for a long time
B)replace the page that has been used for a long time
C)replace the page that will not be used for a long time
D)none of the mentioned

Question 21

LRU page - replacement algorithm associates with each page the___________  

A)time it was brought into memory
B)the time of that page's last use
C)page after and before it
D)all of the mentioned

Question 22

What are the two methods of the LRU page replacement policy that can be implemented in hardware?

A)counters
B)ram & registers
C)stack & counters
D)registers

Question 23

When using counters to implement LRU, we replace the page with the___________

A)smallest time value
B)largest time value
C)greatest size
D)none of the mentioned

Question 24

There is a set of page replacement algorithms that can never exhibit Belady's Anomaly, called___________

A)queue algorithms
B)stack algorithms
C)string algorithms
D)none of the mentioned