10,312 views
7 votes
7 votes

Which of the following algorithm leads convoy effect?

  1. FCFS
  2.   SJF
  3.   Priority scheduling
  4.   All of the above

3 Answers

11 votes
11 votes

Not a answer but Personal Opinion (Actually for this question, every student is just giving opinions only because No one can answer it with 100% certainty, Some students have assumed their own opinion on this question as The Answer , But I don't have that delusion) : 

I have nowhere found where SJF is said to suffer from Convoy effect in any standard text so far. I have done extensive research on internet about this question and I have not found a single standard text in which SJF is said to be suffering from convoy effect. But I have found one standard book in which it is written that SJF doesn’t suffer from Convoy effect.
https://books.google.co.in/books?id=XRf5vw9xlsQC&pg=PA281&lpg=PA281&dq=sjf+convoy+effect&source=bl&ots=3zov2vPeVH&sig=4oQNVodjSxBy3CElxFBxE09Jok0&hl=en&sa=X&ved=0ahUKEwjWvuP4wMLVAhXGK48KHWuxDywQ6AEIjwEwFA#v=onepage&q=sjf%20convoy%20effect&f=false

But I’d say this : Every year many students come up with this doubt and waste significant amount of time arguing yes or no with other students. You shouldn’t do it. This won’t be asked in GATE and If it is asked, Answer only FCFS.

Adding Arjun Sir's comment which tells why answer is Not Clear for this question : 

Currently the answer is not clear as to what convoy effect really means. If that is clear, it can be better understood why FCFS suffers from it and others don't.

edited by
9 votes
9 votes

Convoy Effect: If a process has very high Burst Time, then all other processes which come after that will go to starvation.

FCFS: If first process has very large BT, then all will go to starvation.

SJF: Let P1 come at t=0 having BT=50, after 1 second other processes come having BT=1. all other will go to starvation, bcz there is no preemption.

Priority: If the process having highest priority has BT=50, and all other lower priority processes have BT=1, all other will go to starvation.

Anwer should be All

4 votes
4 votes
FCFS - When first process is large enough then it increases the waiting time of the remaining process

SJF- Would initiallly choose smalller process from the ready queue

Priority Scheduling - It depends solely on the priority assigned by the process thus it may or may not lead to

So the answer is FCFS

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