Question

A variation of the round-robin scheduler is the regressive round-robin scheduler. This scheduler assigns each process a time quantum and a priority. The initial value of a time quantum is 50 milliseconds. However, every time a process has been allocated the CPU and uses its entire time quantum (does not block for I/O), 10 milliseconds is added to its time quantum, and its priority level is boosted. (The time quantum for a process can be increased to a maximum of 100 milliseconds.) When a process blocks before using its entire time quantum, its time quantum is reduced by 5 milliseconds, but its priority remains the same. What type of process (CPU-bound or I/O-bound) does the regressive round-robin scheduler favor? Explain.

Answer 1

The regressive round robin scheduler will favour the CPU-bound processes. Because CPU-bound processes when uses its entire time quantum, they get additionaly 10 milliseconds as time quantum as well as there priority gets boosted.

The regressive round robin scheduler will not favour the I/O-bound processes. Because these processes can be blocked for I/O before consuming the full quota of time quantum, and their priority will not get effected , its mean priority will be same as before.