OS scheduling algorithms implementations

Theory

selection function - chooses a process among ready for execution. Three quantities:

• w = time spend in system so far, waiting ??
• e = time spent in execution so far
• s = total service time required by the process, including e; generally, this quan- tity must be estimated or supplied by the user

HRRN - $$ max(\frac{w+s}{s}) $$

decision mode - when to execute selection function

1. Nonpreemptive - process executes until terminates or blocks to wait for I/O
2. Preemptive - running process can be interrupted at any time

Time measure

• service time (Ts) - total sum of CPU and IO cycles
• turnaround time (Tr) - total time in system. Ts + waiting
• normalized turnaround (Tr/Ts) - relative delay experienced by a process

Lab variant 91582

program input:

CPU(6);IO2(16);CPU(6);IO2(20);CPU(10);IO1(16);CPU(8);IO2(20);CPU(2);IO1(12);CPU(4);IO1(18);
CPU(4);IO2(18);CPU(10);IO2(16);CPU(4);IO1(14);CPU(10);IO1(12);CPU(6);IO1(20);
CPU(2);IO2(12);CPU(6);IO1(16);CPU(4);IO2(12);CPU(2);IO1(14);CPU(6);IO1(12);
CPU(10);IO1(20);CPU(4);IO2(12);CPU(10);IO1(10);CPU(8);IO2(14);CPU(10);IO1(18);
CPU(8);IO2(14);CPU(8);IO2(20);CPU(8);IO1(10);CPU(6);IO2(20);CPU(8);IO2(18);CPU(2);IO2(20);
CPU(12);IO2(10);CPU(48);IO2(18);CPU(12);IO1(18);CPU(24);IO1(14);CPU(48);IO1(20);CPU(24);IO2(14);CPU(36);IO2(10);