Question

How to implement first come first serve scheduling in XV6?

A) Modify the priority assignment algorithm in the scheduler.
B) Replace the existing scheduler with a completely new one.
C) Implement FCFS by default as it is the XV6 default scheduler.
D) Use a custom system call to enforce FCFS scheduling.

Answer 1

To implement first come first serve scheduling in XV6, you would need to replace the existing round-robin scheduler with a new one that selects processes based on their arrival times, ensuring that the one that has been waiting the longest is served first.

Step-by-step explanation:

To implement first come first serve (FCFS) scheduling in XV6, you would need to modify the existing scheduler. XV6 uses a round-robin scheduling algorithm by default, which means that implementing a pure FCFS scheduler would involve significant changes.

Option B would be the correct approach: Replace the existing scheduler with a completely new one. This would entail writing a scheduler that selects the process that has been waiting the longest and runs it next, ignoring priority. The essential steps for this would include updating the process table to track the arrival time of processes and modifying the scheduler function to pick the process with the earliest arrival time.

Keep in mind that strict FCFS scheduling does not always perform well with respect to system responsiveness, especially with interactive processes that could starve under high load conditions.