Process scheduling is a critical component of operating system (OS) design that ensures efficient utilization of CPU resources by managing the execution of multiple processes in a multitasking environment. In this blog post, we will explore the concept of process scheduling in OS, its importance, and various scheduling algorithms.
Process Scheduling in OS
Process scheduling is the process by which the operating system selects a process from the queue of waiting processes and assigns it the CPU for execution. The scheduler is responsible for determining which process to run next based on a set of criteria, including priority, waiting time, and process state.
The process scheduling algorithm is responsible for choosing the process that will run next, taking into account various factors such as the priority of the process, its time spent waiting, and the available resources of the system.
Importance of Process Scheduling
Process scheduling is essential for efficient utilization of the CPU resources of the system. It allows multiple processes to run simultaneously and ensures that each process receives a fair share of the system's resources. Process scheduling also enables the OS to manage the execution of processes in a way that minimizes response time and maximizes throughput.
Process Scheduling Algorithms
There are several process scheduling algorithms, each designed to optimize a specific performance metric. Some of the most commonly used process scheduling algorithms are:
First Come, First Serve (FCFS)
In this algorithm, the process that arrives first is executed first. The CPU is assigned to the first process in the queue, and it continues executing until it completes or is blocked by an I/O request.
Shortest Job First (SJF)
This algorithm selects the process with the shortest estimated execution time next. It reduces the average waiting time of processes by selecting the process that requires the least amount of time to complete.
Round Robin (RR)
This algorithm assigns a fixed time slice to each process in the queue, after which the CPU is allocated to the next process. The process returns to the queue if it does not complete its execution within the allotted time slice.
Priority Scheduling
This algorithm assigns a priority value to each process, and the process with the highest priority is executed first. It can be either preemptive or non-preemptive.
Multilevel Queue
This algorithm divides the process queue into several levels, with each level assigned a different priority value. Processes are assigned to the appropriate level based on their characteristics, such as CPU time required, memory usage, or I/O needs.
Process Scheduling in Practice
To see process scheduling in action, we can use the Linux command-line utility ps. Ps provides a real-time view of the system's processes and their status.
To open ps, open the terminal and type "ps -e" and press enter. This will show a list of all the running processes on the system.
We can use the nice command to set the priority of a process. For example, to set the priority of a process with a PID of 1234 to 5, type "nice -n 5 1234" and press enter. This will set the priority of the process to 5, with a higher priority value indicating a higher priority for execution.
Conclusion
Process scheduling is an essential component of OS design that enables efficient utilization of CPU resources. The process scheduling algorithm is responsible for selecting the process that will run next, taking into account various factors such as priority and waiting time. Understanding process scheduling algorithms is crucial for system administrators and software developers alike, as it allows them to optimize the performance of their systems and applications.
Related: Process Control Block (PCB): The Heart of Process Management in OS