doc/services/cpu_freq/policies/on_demand.rst
.. _on_demand_policy:
On-Demand CPU Frequency Scaling Policy ######################################
The On-Demand policy evaluates the current CPU load using the
:ref:CPU Load metric <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 :zephyr:code-sample:cpu_freq_on_demand 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.