admin-guide/pm/cpufreq.rst

60 As a rule, each governor implements one, possibly parametrized, scaling
81 to bypass the governor layer and implement their own performance scaling
148 scaling governor to it (to begin with, that is the default scaling governor
151 the governor's ``->init()`` callback which is expected to initialize all of the
153 a governor ``sysfs`` interface to it.  Next, the governor is started by
166 on the configuration and capabilities of the scaling driver and the governor.
171 to use the scaling governor previously used with the policy that became
172 "inactive" (and is re-initialized now) instead of the default governor.
177 necessary to restart the scaling governor so that it can take the new online CPU
178 into account.  That is achieved by invoking the governor's ``->stop`` and
182 governor layer of ``CPUFreq`` and provides its own P-state selection algorithms.
216 and what scaling governor is attached to the given policy.  Some scaling drivers
264 	work with the `ondemand`_ governor, -1 (:c:macro:`CPUFREQ_ETERNAL`)
277 	kernel module for the governor held by it to become available and be
298 	The scaling governor currently attached to this policy or (if the
303 	governor to be attached to this policy or a new scaling algorithm
326 	This attribute is functional only if the `userspace`_ scaling governor
329 	It returns the last frequency requested by the governor (in kHz) or can
344 The scaling governor for a given policy object can be changed at any time with
348 algorithms implemented by them.  Those attributes, referred to as governor
350 scaling driver in use.  If the driver requires governor tunables to be
354 subdirectory containing the governor tunables is the name of the governor
360 When attached to a policy object, this governor causes the highest frequency,
363 The request is made once at that time the governor for the policy is set to
370 When attached to a policy object, this governor causes the lowest frequency,
373 The request is made once at that time the governor for the policy is set to
380 This governor does not do anything by itself.  Instead, it allows user space
387 This governor uses CPU utilization data available from the CPU scheduler.  It
396 The actions of this governor for a particular CPU depend on the scheduling class
398 RT or deadline scheduling classes, the governor will increase the frequency to
400 if it is invoked by the CFS scheduling class, the governor will use the
413 This governor also employs a mechanism allowing it to temporarily bump up the
416 is passed by the scheduler to the governor callback which causes the frequency
420 This governor exposes only one tunable:
424 	runs of governor computations (default: 1000 times the scaling driver's
428 	of the governor which might be excessive without it.
430 This governor generally is regarded as a replacement for the older `ondemand`_
440 This governor uses CPU load as a CPU frequency selection metric.
447 If this governor is attached to a policy shared by multiple CPUs, the load is
451 The worker routine of this governor has to run in process context, so it is
454 governor is minimum, but it causes additional CPU context switches to happen
467 This governor exposes the following tunables:
470 	This is how often the governor's worker routine should run, in
475 	for each policy this governor is attached to (but since the unit here
486 	If the estimated CPU load is above this value (in percent), the governor
505 	This causes the next execution of the governor's worker routine (after
515 	governor (including the maximum value used when the ``up_threshold``
526 	where f is the governor's original frequency target.  The default value
546 	will cause the governor to select a frequency lower than its original
553 This governor uses CPU load as a CPU frequency selection metric.
555 It estimates the CPU load in the same way as the `ondemand`_ governor described
564 This governor exposes the following tunables:
567 	Frequency step in percent of the maximum frequency the governor is
573 	and setting it to 100 effectively causes the governor to periodically