JB PANDIT

sdfsdfsfsdfsssgsCPU scheduling is the process of determining which processes in a computer system's ready queue are allocated CPU time, and for how long. This is crucial for optimizing the performance and efficiency of the CPU. The main goals of CPU scheduling are to ensure fairness, maximize CPU utilization, and minimize response and turnaround times for processes. Here are the primary types of CPU scheduling: ### 1. **First-Come, First-Served (FCFS) Scheduling** - **Description**: Processes are scheduled in the order they arrive in the ready queue. - **Advantages**: Simple to understand and implement. - **Disadvantages**: Can lead to the "convoy effect," where short processes get stuck waiting behind long ones, leading to poor average response time. ### 2. **Shortest Job Next (SJN) or Shortest Job First (SJF) Scheduling** - **Description**: Processes with the shortest estimated runtime are scheduled next. - **Advantages**: Can result in the optimal average turnaround time. - **Disadvantages**: Difficult to predict the runtime of processes accurately; may lead to starvation of longer processes. ### 3. **Priority Scheduling** - **Description**: Each process is assigned a priority, and the CPU is allocated to the process with the highest priority. - **Advantages**: Can ensure important tasks are completed first. - **Disadvantages**: Lower priority processes may suffer from starvation; solutions like aging can be used to prevent this. ### 4. **Round Robin (RR) Scheduling** - **Description**: Each process is assigned a fixed time slice (quantum) in a cyclic order. - **Advantages**: Fair and straightforward; each process gets an equal share of the CPU. - **Disadvantages**: Choosing the optimal time quantum is challenging; too small a quantum can lead to high overhead, while too large can resemble FCFS. ### 5. **Multilevel Queue Scheduling** - **Description**: Processes are divided into different queues based on their characteristics (e.g., foreground and background processes), and each queue can have its own scheduling algorithm. - **Advantages**: Can efficiently handle processes with different requirements. - **Disadvantages**: Complex to implement and manage; needs proper balancing to avoid starvation. ### 6. **Multilevel Feedback Queue Scheduling** - **Description**: Similar to multilevel queue scheduling, but processes can move between queues based on their behavior and requirements. - **Advantages**: More flexible and can adapt to the dynamic needs of processes. - **Disadvantages**: Complex to configure and maintain; requires fine-tuning of parameters. ### 7. **Shortest Remaining Time First (SRTF) Scheduling** - **Description**: A preemptive version of SJF, where the process with the shortest remaining time to completion is scheduled next. - **Advantages**: Can further improve turnaround times compared to SJF. - **Disadvantages**: Similar issues with estimating process lengths; may cause more context switches, leading to overhead. ### 8. **Highest Response Ratio Next (HRRN) Scheduling** - **Description**: Priority is given to the process with the highest response ratio, calculated as \( \text{Response Ratio} = \frac{(Waiting Time + Service Time)}{Service Time} \). - **Advantages**: Balances short and long processes better, preventing starvation. - **Disadvantages**: More complex to compute and manage than simpler algorithms. Each of these scheduling algorithms has its own strengths and weaknesses, and the choice of which to use depends on the specific requirements and constraints of the operating system and the types of applications being run.