CPU idle Time

Question

 

Comments

If in 1 minute - 6 processes

Each process - 8 second proceaspro time

=> 6 processes - 48 seconds processing time.

=> In 1 minute, CPU is idle for 60-48=12 seconds.

%idle time = 12/60 *100 = 20%

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@aambazinga, yes you are right, another way to analyses is

 per a minute, there are 6 processes arriving on average ===> in 60 sec, 6 processes

therefore a new process can arrive in 10 sec but arrived process uses 8 seconds BT ===> 2 seconds, cpu idle per process

 

total idle time = 2*6 = 12 sec

total idle time in % = $\frac{12}{60} * 100 $ = 20%

 

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since rate at which process arriving is constant then we can also calculate cpu idle time of one process like

2/10*200=20%  cpu idle time will also be constant!!!!!!

Answer 1

A llitle doubt , if in 60 sec 6 process arrives, doest that mean every 10 seconds process arrives ? Won't the last process that arrived at 60th  second   take 8 seconds more?  I mean is this a possibility to the above question?

Comments

even if u consider that each process arrives at an interval of 10 sec. then for one process, its processing time is 8 sec. so the CPU will be idle for the next 2 seconds and then the next process will arrive and so on...

so idle time in % = 2(idle time)/10(total time considering one process arrival rate) * 100

                            = 20%