MULTILEVEL Queue Scheduling in Operating System | OS Tutorials

In an operating system, the multilevel queue scheduling algorithm has been created for processes that are easily classified into different groups like, Foreground (Interactive) processes and background (Batch) processes. A multilevel queue scheduling algorithm partitions the ready queue into several separate queues, as shown in Figure 1.

• The Processes are permanently assigned to one queue, based on some property of the process, such as memory size, process priority, or process type. Each queue has its own scheduling algorithm.
• There must be scheduling among the queues, which is commonly implemented as fixed-priority preemptive scheduling.
• Multilevel queue scheduling provides a hybrid solution to the problem of providing efficiency and good user service simultaneously.
• As shown in Figure 1, a multilevel queue scheduling algorithm with five queues is listed below in order of priority.
  1. System Processes
  2. Interactive Processes
  3. Interactive Editing Processes
  4. Batch Processes
  5. Student Processes
• Each queue has absolute priority over lower-priority queues. If an Interactive editing process entered the ready queue while a batch process was running, the batch process would be preempted.
• We can also give a time slice to the queues, where each queue gets a certain portion of the CPU time, which it can then schedule among its various processes.