SRTF with IO doubt.

Question

When we have SRTF with IO, in the question they give BURST-TIME 1, IO, BURST-TIME2 .

My doubt is whether to apply SRTF on total burst time (I mean BT1 + BT2) or on part of burst time like consider only BT1 or BT2 at a time before or after IO.

Then answers will change depending on the method we choose the process.

Someone please tell me the correct method with some reference if possible.

Thanks.

Answer 1

It will be given in the question that i/o operation may overlap, because each process can be given its own i/o devices.
P1: BT1 + I/O + BT2, it means a process will be executed by CPU for some time BT1, then it will be in waiting state for i/o operations and then again will be assigned to CPU and will need last cpu time that is BT2.

SRTF will be applied for BT1 and then BT2, but it can be applied for both also for example, Process P1 has executed BT1 and I/O time, now it's about to execute for BT2, and some other process P10 ( for example) is about to start its execution (BT1) then
srtf cpu scheduling will consider both the burst times BT1 and BT2, and will schedule the process which has lesser burst time.

Comments

Actually I was confused because ravidrababu says we must consider total burst time and not BT1 . Also in SJF we schedule P2 first right ?

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yes, correct in SJF also P2 will be scheduled first.

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Thanks a lot !