Lines Matching refs:P
24 For the processors supported by ``intel_pstate``, the P-state concept is broader
27 information about that). For this reason, the representation of P-states used
32 ``intel_pstate`` maps its internal representation of P-states to frequencies too
38 Since the hardware P-state selection interface used by ``intel_pstate`` is
58 or without hardware-managed P-states support and in the passive mode. Which of
70 provides its own scaling algorithms for P-state selection. Those algorithms
73 ``sysfs``). [Note that different P-state selection algorithms may be chosen for
79 For example, the ``powersave`` P-state selection algorithm provided by
83 There are two P-state selection algorithms provided by ``intel_pstate`` in the
85 depends on whether or not the hardware-managed P-states (HWP) feature has been
88 Which of the P-state selection algorithms is used by default depends on the
102 select P-states by itself, but still it can give hints to the processor's
103 internal P-state selection logic. What those hints are depends on which P-state
107 Even though the P-state selection is carried out by the processor automatically,
109 in this mode. However, they are not used for running a P-state selection
119 internal P-state selection logic is expected to focus entirely on performance.
124 Also, in this configuration the range of P-states available to the processor's
125 internal P-state selection logic is always restricted to the upper boundary
126 (that is, the maximum P-state that the driver is allowed to use).
136 internal P-state selection logic to be less performance-focused.
149 CPU scheduler in order to run a P-state selection algorithm, either
158 Without HWP, this P-state selection algorithm is always the same regardless of
161 It selects the maximum P-state it is allowed to use, subject to limits set via
165 This is the default P-state selection algorithm if the
172 Without HWP, this P-state selection algorithm is similar to the algorithm
175 registers of the CPU. It generally selects P-states proportional to the
181 is not touched if the new P-state turns out to be the same as the current
184 This is the default P-state selection algorithm if the
200 hardware in order to change the P-state of a CPU (in particular, the
205 in ``sysfs`` (and the P-state selection algorithms described above are not
211 the entire range of available P-states is exposed by ``intel_pstate`` to the
220 Turbo P-states Support
223 In the majority of cases, the entire range of P-states available to
228 The P-states above the turbo threshold are referred to as "turbo P-states" and
229 the whole sub-range of P-states they belong to is referred to as the "turbo
231 multicore processor to opportunistically increase the P-state of one or more
235 Specifically, if software sets the P-state of a CPU core within the turbo range
237 performance scaling control for that core and put it into turbo P-states of its
240 processors will never use any P-states above the last one set by software for
242 processor generations will take it as a license to use any P-states from the
244 processors setting any P-state from the turbo range will enable the processor
245 to put the given core into all turbo P-states up to and including the maximum
248 One important property of turbo P-states is that they are not sustainable. More
252 be exceeded if a turbo P-state was used for too long.
254 In turn, the P-states below the turbo threshold generally are sustainable. In
257 situation (a higher P-state may still be used if it is set for another CPU in
260 Some processors allow multiple cores to be in turbo P-states at the same time,
261 but the maximum P-state that can be set for them generally depends on the number
262 of cores running concurrently. The maximum turbo P-state that can be set for 3
263 cores at the same time usually is lower than the analogous maximum P-state for
264 2 cores, which in turn usually is lower than the maximum turbo P-state that can
265 be set for 1 core. The one-core maximum turbo P-state is thus the maximum
268 The maximum supported turbo P-state, the turbo threshold (the maximum supported
269 non-turbo P-state) and the minimum supported P-state are specific to the
277 the entire range of available P-states, including the whole turbo range, to the
279 generally causes turbo P-states to be set more often when ``intel_pstate`` is
286 work as expected in all cases (that is, if set to disable turbo P-states, it
296 * The minimum supported P-state.
298 * The maximum supported `non-turbo P-state <turbo_>`_.
300 * Whether or not turbo P-states are supported at all.
302 * The maximum supported `one-core turbo P-state <turbo_>`_ (if turbo P-states
306 of P-states into frequencies and the other way around.
335 Maximum P-state the driver is allowed to set in percent of the
337 P-state <turbo_>`_).
344 Minimum P-state the driver is allowed to set in percent of the
346 P-state <turbo_>`_).
353 Number of P-states supported by the processor (between 0 and 255
354 inclusive) including both turbo and non-turbo P-states (see
355 `Turbo P-states Support`_).
364 range of supported P-states, in percent.
371 If set (equal to 1), the driver is not allowed to set any turbo P-states
372 (see `Turbo P-states Support`_). If unset (equalt to 0, which is the
373 default), turbo P-states can be set by the driver.
380 but it affects the maximum possible value of per-policy P-state limits
386 the processor. If set (equal to 1), it causes the minimum P-state limit
391 This setting has no effect on logical CPUs whose minimum P-state limit
392 is directly set to the highest non-turbo P-state or above it.
437 multiplier to the internal P-state representation used by ``intel_pstate``.
439 attributes are capped by the frequency corresponding to the maximum P-state that
443 not allowed to use turbo P-states, so the maximum value of ``scaling_max_freq``
444 and ``scaling_min_freq`` is limited to the maximum non-turbo P-state frequency.
452 and ``scaling_min_freq`` corresponds to the maximum supported turbo P-state,
459 List of P-state selection algorithms provided by ``intel_pstate``.
462 P-state selection algorithm provided by ``intel_pstate`` currently in
466 Frequency of the average P-state of the CPU represented by the given
485 Coordination of P-State Limits
488 ``intel_pstate`` allows P-state limits to be set in two ways: with the help of
502 P-states, hyper-threading is enabled and on current performance requests
503 from other CPUs. When platform doesn't support per core P-states, the
506 core P-states support, when hyper-threading is enabled, if the sibling CPU
514 change in order to request its internal P-state selection logic to always set
515 P-states within these limits. Otherwise, the limits are taken into account by
517 every time before setting a new P-state for a CPU.
530 user space to help ``intel_pstate`` to adjust the processor's internal P-state
573 interface, but the set of P-states it can use is limited by the ``_PSS``
576 On those systems each ``_PSS`` object returns a list of P-states supported by
577 the corresponding CPU which basically is a subset of the P-states range that can
581 than the frequency of the highest non-turbo P-state listed by it, but the
582 corresponding P-state representation (following the hardware specification)
583 returned for it matches the maximum supported turbo P-state (or is the
586 The list of P-states returned by ``_PSS`` is reflected by the table of
592 of the highest supported non-turbo P-state listed by ``_PSS`` which, of course,
598 (possibly multiplied by a constant), then it will tend to choose P-states below
603 benefit from running at turbo frequencies will be given non-turbo P-states
608 turbo threshold. Namely, if that is not coordinated with the lists of P-states
610 a turbo P-state in those lists and there may be a problem with avoiding the
612 P-states overall, ``acpi-cpufreq`` simply avoids using the topmost state listed
613 by ``_PSS``, but that is not sufficient when there are other turbo P-states in
617 `passive mode <Passive Mode_>`_, except that the number of P-states it can set
643 power capping) that rely on the availability of ACPI P-states
652 Do not enable the `hardware-managed P-states (HWP) feature
657 `hardware-managed P-states (HWP) feature <Active Mode With HWP_>`_ is
669 Use per-logical-CPU P-State limits (see `Coordination of P-state
705 P-state is called, the ``ftrace`` filter can be set to to
718 # entries-in-buffer/entries-written: 80/80 #P:4