GATE CSE Operating System PYQs & Answers — Page 4

Questions 31–40 of 65. Imported answers require independent review unless marked reviewed.

Which one of the following statements is FALSE?

Your answerChoose one option.

The TLB performs an associative search in parallel on all its valid entries using page number of incoming virtual address.

If the virtual address of a word given by CPU has a TLB hit, but the subsequent search for the word results in a cache miss, then the word will always be present in the main memory.

The memory access time using a given inverted page table is always same for all incoming virtual addresses.

In a system that uses hashed page tables, if two distinct virtual addresses V1 and V2 map to the same value while hashing, then the memory access time of these addresses will not be the same.

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Consider four processes P, Q, R, and S scheduled on a CPU as per round robin algorithm with a time quantum of 4 units. The processes arrive in the order P, Q, R, S, all at time t = 0. There is exactly one context switch from S to Q, exactly one context switch from R to Q, and exactly two context switches from Q to R. There is no context switch from S to P. Switching to a ready process after the termination of another process is also considered a context switch. Which one of the following is NOT possible as CPU burst time (in time units) of these processes?

Your answerChoose one option.

P = 4, Q = 10, R = 6, S = 2

P = 2, Q = 9, R = 5, S = 1

P = 4, Q = 12, R = 5, S = 4

P = 3, Q = 7, R = 7, S = 3

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Consider two file systems

and

, that use contiguous allocation and linked allocation, respectively. A file of size 100 blocks is already stored in A and also in B. Now, consider inserting a new block in the middle of the file between the 50ᵗʰ and 51ˢᵗ block, whose data is already available in the memory. Assume that there are enough free blocks at the end of the file and that the file control blocks are already in memory. Let the number of disk accesses required to insert a block in the middle of the file in

and

are

and

, respectively, then the value of

is __________.

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Consider a demand paging system with four page frames (initially empty) and LRU page replacement policy. For the following page reference string

7, 2, 7, 3, 2, 5, 3, 4, 6, 7, 1, 5, 6, 1

the page fault rate, defined as the ratio of number of page faults to the number of memory accesses (rounded off to one decimal place) is __________.

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In the context of operating systems, which of the following statements is/are correct with respect to paging?

Your answerSelect all correct options. You can choose more than one.

Paging helps solve the issue of external fragmentation.

Page size has no impact on internal fragmentation.

Paging incurs memory overheads.

Multi-level paging is necessary to support pages of different sizes.

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Which of the following standard C library functions will always invoke a system call when executed from a single-threaded process in a UNIX/Linux operating system?

Your answerSelect all correct options. You can choose more than one.

exit

malloc

sleep

strlen

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Which of the following statement(s) is/are correct in the context of CPU scheduling?

Your answerSelect all correct options. You can choose more than one.

Turnaround time includes waiting time.

The goal is to only maximize CPU utilization and minimize throughput.

Round-robin policy can be used even when the CPU time required by each of the processes is not known apriori.

Implementing preemptive scheduling needs hardware support.

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Consider a linear list based directory implementation in a file system. Each directory is a list of nodes, where each node contains the file name along with the file metadata, such as the list of pointer to the data blocks. Consider a given directory foo. Which of the following operations will necessarily require a full scan of foo for successful completion?

Your answerSelect all correct options. You can choose more than one.

Creation of a new file in foo

Deletion of an existing file from foo

Renaming of an existing file in foo

Opening of an existing file in foo

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Three processes arrive at time zero with CPU bursts of 16, 20 and 10 milliseconds. If the scheduler has prior knowledge about the length of the CPU bursts, the minimum achievable average waiting time for these three processes in a non-preemptive scheduler (rounded to nearest integer) is ________ milliseconds.

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Consider the following multi-threaded code segment (in a mix of C and pseudo-code), invoked by two processes P1 and P2, and each of the processes spawns two threads T1 and T2:

int x = 0; // global

Lock L1; // global

main() {

create a thread to execute foo(); // Thread T1

create a thread to execute foo(); // Thread T2

wait for the two threads to finish execution;

print (x);

}

foo() {

int y = 0;

Acquire L1;

x = x + 1;

y = y + 1;

Release L1;

print (y);

}

Which of the following statement(s) is/are correct?

Your answerSelect all correct options. You can choose more than one.

Both P1 and P2 will print the value of x as 2.

At least one of P1 and P2 will print the value of x as 4.

At least one of the threads will print the value of y as 2.

Both T1 and T2, in both the processes, will print the value of y as 1.

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GATE CSE Operating System PYQs

Question 38

Question 42

Question 63

Question 64

Question 11

Question 14

Question 14

Question 15

Question 25

Question 42