CPU Scheduling (SRTF)

Question

I have solved this but not getting the answer…. will any one verify its correctness plz

Thank you:)

 

Comments

the solution is perfectly alright !

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@Shaik Masthan, do we consider total time = BT+Bt or individual BT?

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Total BT = Before I/O BT + After I/O BT

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then please check after p4 in 8th clock p1 will be scheduled or p3? because p1 is having total burst remaining 4 and p3 is having only 2. because if you check in this video which i have posted he is considering scheduling on the basis of total remaining burst time. Please clarify...?

https://www.youtube.com/watch?v=EvWdPgK9Jt8&feature=youtu.be&list=PLEbnTDJUr_If_BnzJkkN_J0Tl3iXTL8vq&t=476

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Yes that's where I ran into problem ... actually I was following the method zs in the above video (i.e. we have to consider the total BT) but using this I was unable to get the answer as shown in the solution

@Shaik Masthan 

please try solving it .... u will find the problem

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so the answer is 5.5,87.5%?

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@Shubhgupta

At that point P1 require 2 BT ( Before I/O ), and P3 requires  2 BT ( After I/O ),

then as per FCFS, P1 get chance !

 

@Nandkishor3939

please try solving it .... u will find the problem

what it means ? 

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yes @Shaik Masthan, that i understood but actually according to that video which i have posted he is considering remaining burst according to total burst not by before I/o or after I/o. So according to his procedure P1 is having total burst 4 unit and P3 is having 2 burst so by shortest p1 will get chance? don't know which method i need to follow.

Please confirm brother.. :).

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in SRTF ..the schediling criteria based on total Burst time ..I/O time is not considered for scheduling criteria

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@jatin khachane 1 @Shaik Masthan

Please make it clear that

1] we have to use the total BT for SRTF(by this method i am getting the answer)

or

2] we have to consider the First BT and second BT separately

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Even I used to follow Sir's method of solving sums involving both CPU BT and IOBT. But I never got the correct answer using this method. So I changed the method to the one which @Shaik Masthan

mentioned. This method is correct.

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@Somoshree Datta 5

can you please such example where you got it wrong any prev year ques

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jatin khachane 1

didnt come across such a previous year question. But you can refer this link too https://gateoverflow.in/164723/srtf-with-io-doubt

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check these two videos also which mentioned in link's comment they also used the total burst time .

https://gateoverflow.in/128441/cpu-scheduling-srtf-with-i-o-example?show=128570#c128570.. 

according to Sir's answer he also considered total compute time -https://gateoverflow.in/251148/gatebook-2019-os1-20?show=285743#a285743 and then processed accordingly.

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Shubhgupta

in this link that u mentioned https://gateoverflow.in/251148/gatebook-2019-os1-20?show=285743#a285743

Why wasnt P2 preempted at time t=14? Shouldnt the tie be broken when both P1 and P2 have the same BTs by considering the process to schedule which is having lower process id (since here arrival times are also same, so we cant use arrival time as a criteria)?This is really confusing..:(

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@Shubhgupta   

What is difference between shortest compute time first in that gatebook question shortest compute time first is used and shortest remaining time first ??

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i think both are same shortest remaining compute time first and shortest remaining time first.

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@Shubhgupta

I think the video is misleading .... its wrong !!

Answer 1

This will be helpful..

Comments

May be they used different approach. But mine is the standard approach

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Have you solved some questions by your approach and got correct answer in these type of questions

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Yes, just solve previous year questions. it is enough.