#Galvin #CpuScheduling SJF VS SRTF Average waiting time doubt.

Question

Let's say we have two CPU scheduling algorithm as SJF and SRTF and we have a arbitrary pool/set of processes with  different ARRIVAL TIME and CPU BURST, then what CPU scheduling algorithm will result in minimum average waiting time?

Note : We know, with processes having same arrival time will make SRTF to SJF and SJF guarantees minimum average waiting time, but here arrival time of processes is not same.

Moreover please consider this screenshot from Galvin - in this screenshot below the avg waiting time of SRTF is less than SJF, but my doubt is, is this valid for only this set of values or when arrival times are different than SRTF will ALWAYS have the less average waiting time over SJF?

Comments

if arrival time same and burst time also same

then also SJF ans SRTF will give same waiting time

 

Then I think, SRTF and SJF is simply behaving like FCFS.

---

Its possible that SRTF is converted to SJF but will never give less than SJF average waiting time it may be equal or greater

It must be SJF's avg waiting time is always greater than or equal to that of SRTF?  

---

hope that will help

https://www.geeksforgeeks.org/difference-between-sjf-and-srjf-cpu-scheduling-algorithms/