Question

Compatible Timesharing System (CTSS) has a priority scheduler. A process initially gets 1 quanta of time, then 2 quanta, then 4 quanta, 8 quanta, 16 quanta, 32 quanta, and 64 quanta where quanta is the length of the time quantum. Between time quanta, the process is swapped out. Thus for a process that has a service time of 100, it would take 7 swaps to disk (including when it was loaded into memory for the first time). Suppose a process had a service time of 30, how many times must it be swapped in before it complete using the CTSS

Answer 1

When The Process has CTSS as 30

Lets See how many Times The Process is Swapped

1. It was loaded into memory for the first time so 1 Swap And run for Time Quantum 1

Remaining CTSS = 29

2.Now It gets swapped and run for time quantum 2

Remaining CTSS = 27

3. Again Swap and run for time quantum of 4

Remaining CTSS = 23

4 Again Swap and run for time quantum of 8

Remaining CTSS = 15

5. Swapped Last Time and run for time quantum of 15 only .

Remaining CTSS =0

Hence Total Number of Swaps = 5 ( including when it was loaded into memory for the first time).

This is how we can get the number of swaps for any process in given time quantums

Thank You

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