UGC NET CSE | January 2017 | Part 2 | Question: 39

Question

Which of the following scheduling algorithms may cause starvation ?

1. First-come-first-served

2. Round Robin

100. Priority

500. Shortest process next

5. Shortest remaining time first 

• A. a, c and e
• B. c, d and e
• C. b, d and e
• D. b, c and d

Answer 1

1. First-come-first-served- No starvation
2. Round Robin-  No starvation
3. Priority- starvation if higher priority process called again and again, lower priority starves
4. Shortest process next -starvation possible
5. Shortest remaining time first -starvation possible as its a preemptive version of shortest process next casuing apotential for longer processes to starve.

so option 2---  c,d,e

Comments

how is it true for 5?

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As the Shortest remaining time first scheduling is a preemptive version of shortest job scheduling. It may cause starvation as shorter processes may keep coming and a long CPU burst process never gets CPU.

from wiki:- Like shortest job first, it has the potential for process starvation; long processes may be held off indefinitely if short processes are continually added. This threat can be minimal when process times follow a heavy-tailed distribution.^[1] A similar algorithm which avoids starvation at the cost of higher tracking overhead is Highest response ratio next.

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In FIFO how starvation not possible, as if first process takes longer time then last process can cause starvation.

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1. In First Come First Serve(FCFS) if a process with a very large Burst Time comes before other processes, the other process will have to wait for a long time but it is clear that other process will definitely get their chance to execute, so it will not suffer from starvation.

Answer 2

answer is (2)c,d and e

Answer 3

Out of the given protocols, only round-robin is sure of not getting the starvation. However, we can assume FCFS to be starvation-free (Only by looking at the options).

option is B

Answer 4

 Starvation is the name given to the indefinite postponement of a process because it requires some resource before it can run, but the resource,
though available for allocation, is never allocated to this process.
1. Priority: A process ready to run for CPU can wait indefinitely because of low priority.
2. Shortest process next : longest process possibility to get starvation.
3. Shortest remaining time first: longest process possibility to get starvation.
Solution: Aging
FCFS and Round Robin scheduling never happen indefinite blocking.

ANS B