On-Demand CPU Frequency Scaling Policy

The On-Demand policy evaluates the current CPU load using the CPU Load metric, and compares it to the trigger threshold defined by the SoC P-state definition.

The On-Demand policy will iterate through the defined P-states and select the first P-state for which the CPU load is greater than or equal to the defined threshold.

If no P-state matches (i.e., the CPU load is below all thresholds), the policy will select the last P-state in the soc_pstates array (the lowest performance state). This is intrinsic to the policy: P-states must be defined in decreasing threshold order in devicetree, and the last P-state will be used for loads below all thresholds.

For an example of the on-demand policy refer to the On-demand CPU frequency scaling sample.

This policy is reactive. Frequency adjustments occur only after a change in system load has been observed, so it cannot anticipate sudden high loads. The policy has no notion of task deadlines and should not be considered as a real-time policy.