OS memory management

1. Which one of the following is the address generated by CPU?

• physical address

• absolute address

• logical address

• none of the mentioned

2.Run time mapping from virtual to physical address is done by ____________

• Memory management unit

• CPU

• PCI

• None of the mentioned

3.The address of a page table in memory is pointed by ____________

• stack pointer

• page table base register

• page register

• program counter

4.Which of the following page replacement algorithms suffers from Belady’s anomaly?

• FIFO

• LRU

• Optimal

• Both LRU & FIFO

5.What is the swap space in the disk used for?

• Saving temporary html pages
  
  

• Saving process data

• Storing the super-block

• Storing device drivers
  

6.A CPU generates 32-bit virtual addresses. The page size is 4 KB. The processor has a translation look-aside buffer (TLB) which can hold a total of 128 page table entries and is 4-way set associative. The minimum size of the TLB tag is:

• 11 bits
  
  

• 13 bits

• 15 bits

• 20 bits

7.Thrashing occurs when

• When a page fault occurs
  
  
  

• Processes on system frequently access pages not memory

• Processes on system are in running state

• Processes on system are in waiting state

8.Consider the virtual page reference string 1, 2, 3, 2, 4, 1, 3, 2, 4, 1 On a demand paged virtual memory system running on a computer system that main memory size of 3 pages frames which are initially empty. Let LRU, FIFO and OPTIMAL denote the number of page faults under the corresponding page replacements policy. Then

• OPTIMAL < LRU < FIFO
  

• OPTIMAL < FIFO < LRU

• OPTIMAL = LRU

• OPTIMAL = FIFO

9.Let the page fault service time be 10ms in a computer with average memory access time being 20ns. If one page fault is generated for every 10^6 memory accesses, what is the effective access time for the memory?

• 21ns
  
  
  

• 30ns

• 23ns

• 35ns

10.A process has been allocated 3 page frames. Assume that none of the pages of the process are available in the memory initially. The process makes the following sequence of page references (reference string): 1, 2, 1, 3, 7, 4, 5, 6, 3, 1 If optimal page replacement policy is used, how many page faults occur for the above reference string?

• 7
  

• 8

• 9

• 10