December 11, 2019
Amitraj
Process Scheduling
-> The process scheduling is the activity of the process manager that handles the removal of the running process from the CPU and the selection of another process on the basis of a particular strategy.
-> Process scheduling is an essential part of multi-programming operating systems. such OS allow more than one process to be loaded into the executable memory at a time and the loaded process shares the CPU using time multiplexing.
Process Scheduling Queues
The OS maintains all PCB's in process scheduling queues. The OS maintains a seperate queue for each of the process states and PCB's of all processes in the same execution state are placed in the same queue. when the state of a process is changed, it PCB is unlinked from its current queue and moved to its new state queue.
* OS maintains following important process scheduling queues:-
1. Job queue- This queue keeps all the processes in the system.
2. 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.
3. Device queue- The processes which are blocked due to unavailability of an I/O device constitute this queue.
-> The OS can different policies to manage each queue (FIFO,round robin, priority etc.) The OS schedular 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.
-> The process scheduling is the activity of the process manager that handles the removal of the running process from the CPU and the selection of another process on the basis of a particular strategy.
-> Process scheduling is an essential part of multi-programming operating systems. such OS allow more than one process to be loaded into the executable memory at a time and the loaded process shares the CPU using time multiplexing.
Process Scheduling Queues
The OS maintains all PCB's in process scheduling queues. The OS maintains a seperate queue for each of the process states and PCB's of all processes in the same execution state are placed in the same queue. when the state of a process is changed, it PCB is unlinked from its current queue and moved to its new state queue.
* OS maintains following important process scheduling queues:-
1. Job queue- This queue keeps all the processes in the system.
2. 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.
3. Device queue- The processes which are blocked due to unavailability of an I/O device constitute this queue.
-> The OS can different policies to manage each queue (FIFO,round robin, priority etc.) The OS schedular 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.
