Can any one please explain the both processes for feedback scheduling?

Table 9.4 Process Scheduling Example Process Arrival Time Service Time served (FCFS 3 Round robin Round robin Shortest peocess next (SPN Shomest remainingB time (SRT Highest response ratio next (HRRN) c Feedback(FB) Feedhack (FB) Figure 9.10 Feedback Scheduling There are a number of variations on this scheme. A simple version is to perform preemption in the same fashion as for round robin: at periodic intervals. Our example shows this (see Figure 9.5 and Table 9.5 ) for a quantum of one time unit. Note that in this case, the behavior is similar to round robin with a time quantum of q-1. One problem with the simple scheme just outlined is that the turnaround time of longer processes can stretch out alarmingly. Indeed, it is possible for starvation to occur if new jobs are entering the system frequently. To compensate for this, we can vary the preemption times according to the queue: A process scheduled from RQ0 is allowed to execute for one time unit and is then preempted; a process scheduled from RQ1 is allowed to execute two time units, and so on. In general, a process scheduled from RQi is allowed to execute q2 time units before preemption. This scheme is illustrated for our example in Figure 9.5 and Table 9.5 Even with the allowance for greater time allocation at lower priority, a longer process may still suffer starvation. A possible remedy is to promote a process to a higher-priority queue after it spends a certain amount of time waiting for service in its current queue