Selfish Round Robin (SRR) is a CPU scheduling algorithm that is designed to provide more CPU time to processes that have a higher priority. It is a variation of the traditional Round Robin scheduling algorithm, with the added feature that each process can "selfishly" increase its own priority.
In SRR, processes are assigned a priority level, with higher priority processes receiving more CPU time than lower priority processes. The priority of a process can change dynamically based on its behavior, such as how long it has been waiting for the CPU or how much CPU time it has used.
An example of SRR is as follows:
Consider a computer system that has three processes, A, B, and C, each with a different priority level. Initially, process A has the highest priority, followed by B and then C. Each process is given a small time slice of the CPU, in a round robin fashion.
At any given time, a process can increase its own priority by making a request to the operating system. If a process requests a priority increase, the operating system will grant the request and adjust the priority levels of all processes accordingly.
For example, if process B requests a priority increase, the operating system will adjust the priority levels so that B has a higher priority than A and C. This means that B will receive more CPU time in the next round robin cycle.
However, if a process uses its time slice excessively, it may cause other processes to wait for an extended period of time. To prevent this, the operating system can also decrease the priority of a process that uses an excessive amount of CPU time. This encourages processes to use the CPU efficiently, rather than hogging the CPU.
This example demonstrates the basic idea behind SRR, where each process can dynamically adjust its own priority based on its behavior, such as how long it has been waiting for the CPU or how much CPU time it has used. This results in a more efficient use of CPU time, as high priority processes receive more CPU time, and a more predictable response time for higher priority processes.
In practice, SRR can be implemented in different ways, with different criteria for increasing or decreasing the priority of a process. For example, the operating system could consider the amount of time a process has been waiting for the CPU, the amount of CPU time it has used, or the size of its data structures. The operating system could also use different algorithms for adjusting the priority of processes, such as decreasing the priority of a process gradually over time, or resetting the priority of a process after a certain period of time.
Another example of SRR is as follows:
Consider a computer system that has four processes, X, Y, Z, and W, each with a different priority level. Initially, process X has the highest priority, followed by Y, Z, and W. Each process is given a small time slice of the CPU in a round robin fashion.
At any given time, a process can request a priority increase, and the operating system will adjust the priority levels accordingly. For example, if process Y requests a priority increase, the operating system will adjust the priority levels so that Y has a higher priority than X, Z, and W. This means that Y will receive more CPU time in the next round robin cycle.
However, if a process uses its time slice excessively, the operating system can decrease its priority. For example, if process W uses an excessive amount of CPU time, the operating system could decrease its priority so that it receives less CPU time in the next round robin cycle.
This example demonstrates how SRR can be used to provide more CPU time to processes that have a higher priority and how processes can dynamically adjust their own priority based on their behavior. By allowing processes to adjust their own priority, SRR provides a more flexible and efficient use of CPU time, as higher priority processes receive more CPU time, and a more predictable response time for high priority processes.
In conclusion, Selfish Round Robin (SRR) is a CPU scheduling algorithm that provides a more flexible and efficient use of CPU time compared to traditional Round Robin scheduling. By allowing processes to adjust their own priority based on their behavior, SRR provides a more predictable response time for high priority processes, while encouraging processes to use the CPU efficiently. This results in a more effective and efficient computer system.
