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Choose the correct alternatives (more than one can be correct) and write the corresponding letters only:

Indicate all the false statements from the statements given below:

(a). The amount of virtual memory available is limited by the availability of the secondary memory

(b). Any implementation of a critical section requires the use of an indivisible machine- instruction ,such as test-and-set.

(c). The use of monitors ensure that no dead-locks will be caused .

(d). The LRU page-replacement policy may cause thrashing for some type of programs.

(e). The best fit techniques for memory allocation ensures that memory will never be fragmented.

asked in Operating System by Veteran (68.8k points) | 1.2k views
The use of monitors ensure mutual exclusion but not deadlock

The LRU page-replacement policy may cause thrashing for some type of programs.

somone pls help.wht does it mean

if u consider the sequence like 12341234......... assume no of frames is 3 then here every page results page fault in LRU It leads to lot of page movements so it causes thrashing
Option b is true. Peterson solution cannot guarantee mutual exclusion. This line is mentioned in Galvin itself. In fact without the use of atomic instruction synchronization cannot be guaranteed.

4 Answers

+16 votes
Best answer
A) A is true.

B) This is false. Example :- Peterson's solution is purely software based solution without use of hardware.

https://en.wikipedia.org/wiki/Peterson's_algorithm

C) False. Reference -> https://en.wikipedia.org/wiki/Monitor_(synchronization)

D) True. This will happend if page getting replaced is immediately refered in next cycle.

E) False.Memory can get fragmented with First fit.
answered by Veteran (48.5k points)
selected by
Updated.

why b is false?

option b should be true.
B is false- reason already given in answer.

Arjun Sir , 

In Option B) 

This is false. Example :- Peterson's solution is purely software based solution without use of hardware.

Sir but the context here is if we need indivisible machine instructions or not ?

So both {test and set (which uses hardware) } and {peterson's solution (which uses Software Implementation) } will fall in the same category according to the context.So it should be true.

Where am I going wrong ?

Can you explain option E.It asks about best fit and your are saying first fit.It can be a typeo.Please verify
@Arjun sir. How can monitor causes deadlock?
Whatever be the case "External Fragmentation" can occur is all three types i.e best fit, first fit, wrost fit.

That might be an typeo in the answer for part E. But answer is correct the statement is false.
+2 votes

before answering some points to know:-

  • Monitor is one of the ways to achieve Process synchronization. Monitor is supported by programming languages to achieve mutual exclusion between processes.
  • Peterson's solution is the purely software-based solution without the use of hardware.
     
  • if u consider the sequence like 12341234......... assume no of frames is 3 then here every page results page fault in LRU It leads to a lot of page movements so it causes thrashing
  • now go and see selected answer 
answered by Boss (7.3k points)
+1 vote
A is true as amount of virtual memory is limited by length of MAR and available secondary storage.

D is false as best fit technique causes internal fragmentation.

Not sure about B and C.
answered by Veteran (35.8k points)
+1 vote

a) True.Link

b)False

c)

d)In any replacement policy thrashing could happen, but it mainly causes in time sharing system

thrashing

e) False. It minimize fragmentation onlyLink

answered by Veteran (76.6k points)
@srestha in best fit there will be external fragmentation right
Please explain option c!!!

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