SKYSPIN
The Operating System maintains the following important process scheduling queues −
The OS can use different policies to manage each queue (FIFO, Round
Robin, Priority, etc.). The OS scheduler determines how to move
processes between the ready and run queues which can only have one entry
per processor core on the system; in the above diagram, it has been
merged with the CPU.
Process Scheduling Queues
The OS maintains all PCBs in Process Scheduling Queues. The OS maintains a separate queue for each of the process states and PCBs of all processes in the same execution state are placed in the same queue. When the state of a process is changed, its PCB is unlinked from its current queue and moved to its new state queue.The Operating System maintains the following important process scheduling queues −
- Job queue − This queue keeps all the processes in the system.
- Ready queue − This queue keeps a set of all processes residing in main memory, ready and waiting to execute. A new process is always put in this queue.
- Device queues − The processes which are blocked due to unavailability of an I/O device constitute this queue.
The OS can use different policies to manage each queue (FIFO, Round
Robin, Priority, etc.). The OS scheduler determines how to move
processes between the ready and run queues which can only have one entry
per processor core on the system; in the above diagram, it has been
merged with the CPU.
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