Core behavior and first-principles view

Scheduler policy is a system-level decision, not a style preference. Cooperative and preemptive models trade simplicity, responsiveness, and shared-state complexity differently.

Cooperative scheduling depends on explicit yield behavior from every runnable task.

Preemptive scheduling improves response latency but requires stronger synchronization discipline.

Policy should map to timing guarantees and fault containment requirements.

Low-level model and equations

CPU utilization framing:

Where:

• $C_i$: execution time
• $T_i$: period

How to build this correctly in practice

Implementation sequence:

1. List hard and soft timing requirements before selecting model.
2. Prototype representative workloads under both policies and measure latency/jitter.
3. Quantify synchronization overhead in preemptive path.
4. Document policy rationale for maintainers and reviewers.

Common failure patterns and review checks

• One non-yielding task can stall cooperative systems.
• Preemptive systems without lock discipline can fail nondeterministically.
• Priority inversion and starvation must be considered explicitly.
• Policy changes should be accompanied by timing regression tests.

Use measurable behavior to choose policy; clarity in requirements beats assumptions about “best” scheduler style.