Operating System

Variable partition memory allocation can lead to?
(i) external fragmentation
(ii) internal fragmentation
(iii) both (i) and (ii)
(iv) none of these

Virtual memory is
(i) an extremely large main memory
(ii) an extremely large secondary memory
(iii) an illusion of an extremely large memory
(iv) a type of memory used in supercomputer

In which of the following page replacement policy Belady's anomaly occurs?

(i) FIFO
(ii) LRU
(iii) LFU
(iv) NRU

In demand paging, pages are:
(i) Loaded only when they are required during execution
(ii) Loaded all at once before execution begins
(iii) Never removed from main memory
(iv) Loaded in random order

If a process has 24 k bytes logical address space and the page size is 4096 bytes then the number of frames of that process is?
(i) 12
(ii) 6
(iii) 8
(iv) 16

Internal fragmentation occurs when

(i) Processes are swapped out
(ii) Pages are missing
(iii) Memory is completely utilized
(iv) Unused space exists within an allocated memory partition

Which page replacement algorithm replaces the page that will not be used for the longest period in the future?

(i) Optimal
(ii) Second Chance
(iii) FIFO
(iv) NRU

Which memory allocation policy allocates the largest hole to the process?

(i) Best-fit
(ii) Worst-fit
(iii) First-fit
(iv) None of the above.

Physical memory is broken into fixed-sized blocks called

(i) frames
(ii) pages
(iii) backing store
(iv) None of the above

What do you understand by address binding, Explain the various address binding schemes.

Consider the virtual page reference string 0, 4, 8, 20, 24, 36, 44, 12, 68, 72, 80, 84, 28, 32, 88, 92 on a demand paged virtual memory system running on computer system that has main memory of size 4 page frames which one initially empty. The CPU uses LRU page replacement policy.
(i) How many page faults does this sequence cause?
(ii) What are the page numbers of the pages present in the main memory at the end of the sequence?

Compare between compile-time, load-time and execution-time address binding.

What is virtual memory? How is it implemented? Explain TLB in virtual memory with neat diagram.

What is the purpose of modify bit in page table.

What is the difference between fixed partition and variable partition also explains the need of compaction.

Explain paging with translation look-aside buffer (TLB) scheme with suitable diagrams.

What is thrashing. Explain the main cause of thrashing. How can we limit the effects of thrashing.

Consider the following page reference string:
7, 2, 3, 1, 2, 5, 3, 4, 6, 7, 7, 1, 0, 5, 4, 6, 2, 3, 0, 1.
How many page faults would occur for the FIFO, LRU and Optimal page replacement algorithms, assuming demand paging with four frames? Remember that all frames are initially empty, so first unique pages will cost one fault each.

What is the cause of thrashing? How does the system detect thrashing and once detected what can the system do to eliminate it

What is Belady's Anomaly? Why LRU and Optimal Page Replacement algorithm doesn't suffer from this problem.

Consider the main memory with the capacity of 4 page frames. Assume that the pages of a process are referenced in the order as given below:
1, 3, 4, 4, 3, 2, 1, 7, 5, 6, 4, 2, 1, 2

Which of FIFO or LRU would be better in this case as a page replacement policy? Why?

How many page faults would occur for the following reference string for four page frames and three page frames using LRU and FIFO algorithms:

1, 2, 3, 4, 5, 5, 3, 4, 1, 6, 7, 8, 7, 8, 9, 7, 8, 9, 5, 4, 5, 4, 2.

What do you understand by fragmentation. Explain the difference between internal and external fragmentation.

What is Thrashing? When does it occur? How can one avoid it?

Consider a paging hardware with a TLB. Assume that the entire page table and all the pages are in the physical memory. It takes 10 milliseconds to search the TLB and 80 milliseconds to access the physical memory. If the TLB hit ratio is 0.6, find the effective memory access time (in milliseconds).

Consider the main memory with the capacity of 4 page frames. Assume that the page of process are referenced in the order as given below:
1, 3, 4, 4, 3, 2, 1, 7, 5, 6, 4, 2, 1, 2
Which of FIFO or LRU would be better in this case as a page replacement policy? Why?

Explain the Address Translation mechanism in Paging. Why is the page size normally some power of two?

Explain the use of TLB in paging hardware and its benefits.

Given five memory partition of 100 KB, 500 KB, 200 KB, 300 KB, and 600 KB(in order), how would the first-fit and best-fit algorithms place processes of 212 KB, 417 KB, 112 KB, and 426 KB (in order)? Which algorithm makes the most efficient use of memory?

Write short notes on: Inverted Page Table

Write short notes on: Paging

Write a short note on:

Paging and segmentation

Write a short note on:

Contiguous Memory allocation

Write short notes on: Belady's Anomaly