Schedulers that take decisions at run-time

The scheduler in an operating system is responsible for determining which processes should be allocated CPU time and in what order. There are different types of schedulers, including preemptive and non-preemptive schedulers. However, the scheduler that takes decisions at run-time is the dynamic scheduler.

Dynamic Scheduler
A dynamic scheduler is a type of scheduler that makes decisions at run-time based on the current state of the system. It takes into account factors such as process priority, resource availability, and system load to determine the optimal scheduling decisions.

Key Features of Dynamic Scheduler:
1. Real-time Decision Making: The dynamic scheduler continuously monitors the system and makes scheduling decisions on the fly. It adapts to the changing conditions of the system and adjusts the allocation of resources accordingly.

2. Consideration of Process Priority: The dynamic scheduler considers the priority of processes when making scheduling decisions. Higher priority processes are given preferential treatment and are allocated CPU time before lower priority processes.

3. Resource Allocation: The dynamic scheduler takes into account the availability of system resources such as CPU, memory, and I/O devices. It ensures that processes are scheduled in a way that maximizes resource utilization and minimizes resource contention.

4. Load Balancing: The dynamic scheduler aims to balance the load across the system by distributing the workload evenly among the available CPUs. It prevents any single CPU from being overloaded while others are idle.

5. Adaptability: The dynamic scheduler adjusts its scheduling decisions based on the workload and system conditions. It can dynamically change the scheduling algorithm or parameters to optimize system performance.

Comparison with Other Schedulers:
- Preemptive Scheduler: A preemptive scheduler can interrupt a running process and allocate CPU time to another process with higher priority. However, the decision to preempt a process is made based on predefined rules and not at run-time. Therefore, it does not meet the criteria of taking decisions at run-time.

- Non-preemptive Scheduler: A non-preemptive scheduler allows a process to continue running until it voluntarily releases the CPU or completes its execution. It does not make decisions at run-time but rather follows a predefined scheduling algorithm.

- Static Scheduler: A static scheduler uses a fixed scheduling algorithm that is determined before the execution of the system. It does not adapt to the changing conditions of the system and cannot make decisions at run-time.

In conclusion, the dynamic scheduler is the only option among the given choices that takes decisions at run-time based on the current state of the system. It continuously monitors the system, considers process priority and resource availability, and dynamically adjusts the scheduling decisions to optimize system performance.