process scheduling

Question

Answer 1

Indefinite blocking or indefinite waiting means starvation and not Convoy Effect.Convoy Effect just increases the waiting time of a process but does not lead to indefinite waiting.The order in which they are in the  ready queue(ready state) , they are going to be executed in the same order although it may take more time(Convoy Effect) , but FCFS gives surety that a process will be executed.

Round robin is practically used scheduling algo since it ensures time sharing between all processes.So this also does not lead to starvation.

What we are left with SRTF and priority scheduling.Both of these may lead to starvation.Consider a process have a higher burst time and currently a process with a lower burst time is executed.As soon as this process completes execution , it is quite possible that a process with lower burst time(or higher priority) arrives in the ready queue , then it has to be transferred to "running state" first.So processes with further lower burst times or higher priorities may continue to arrive as a result of which the process which has higher burst time (or lower prioirity) will not get a chance at all.In short starvation will occur.

Hence the  correct answer should be both B) and D)

Comments

Yes, you are right.  because stream of higher-priority processes can prevent a low-priority process from ever getting the CPU

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I guess answer should be B only.

bocz in priority we use the concept of aging(increasing the priority of the process), So, even the process is waiting still its priority get increased and eventually it will get execute.

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Question asking CAN, Not always , Thats y B and D. 

Answer 2

m bit confused that indefinite blocking means convoy effect or not here..if it is convoy effect than FCFS shows it..suppose a process with very large burst time arrives ..then it will block all other short processes for very long time...SJF also shows this convoy effect..
In a multiprogramming system, if multiple processes are waiting for the CPU for execution and a slow processing process is utilizing the CPU then due to the convoy all fast processes waiting for CPU waits for unnecessarily long time. This is convoy effect.

it means indefinite blocking or not m not sure....because in SRTF there is no convoy effect...process with least burst times are selected...in round robin...(it;s not even in the scene)....

so i think SRTF and priority should be options as they are preemptive and it is possible that other processes might not get a chance and a process with least burst time keeps on arriving....or in case of priority scheduling a process with higher priority keeps on arriving..then it could starv other processes...

n sure whether convoy effect and indefinite blocking means same or not

Comments

yes , so what is ur answer?

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ill go with SRTF and priority scheduling

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my doubt is are convay effect and indefinite blocking different?

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or convoy effect means blocking for a long time but not infinite
and infinite bloacking means forever?

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no they are not different. convoy effect causing starvation

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means FCFC and SJF shows convoy effect where a process can get starved for a long time but not for infinity

and SRTF and priority schduling can lead to infinite blocking..isnt it?

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Indefinite blocking is a problem with priority scheduling algorithms. and SRTF is a priority scheduling algorithm where higest priority is given to the process with least burst time.

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yes ,as more number of process may cause to wait a single process, so priority sechduling causes starvation.

But in FCFS every process will have to wait a finite amount of time. After a finite processes execution it must be a process in  the ready queue to execute next. So, it shouldnot tell starvation.