GATE Overflow Test Series | Operating Systems | Test 2 | Question: 5

Question

Which of the following is correct, regarding thrashing? (Mark all the appropriate choices)

• A. Increasing the degree of multiprogramming can help in reducing thrashing
• B. Priority page replacement can limit the effects of thrashing
• C. Thrashing can be avoided by allocating maximum number of page frames to the process needing the maximum amount of memory
• D. Thrashing decreases the CPU utilization

Answer 1

Thrashing occurs when the size of all locality (set of pages used together) across all the running processes exceeds the memory size. So, increasing the degree of multiprogramming can only worsen thrashing. Option A is false.

Option C is also false as even if the process needing the maximum number of page frames gets the maximum number of page frames, it might need further page frames causing page replacements and thus can lead to thrashing.

Options B and D are TRUE.

Comments

Can you please explain, How Priority page replacement can limit the effects of thrashing?

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Source: Galvin

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When a process is allocated the maximum number of frames and it is still causing thrashing, can such a process ever be executed in any system.? I think option c could also be true if we assume that main memory has enough frames to run a process.

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explanation of C is not satisfactory, when process already gets it”s max need done why it will allocate more. it must complete it’s execution in this case.