Lines Matching refs:intel_pstate
2 ``intel_pstate`` CPU Performance Scaling Driver
13 ``intel_pstate`` is a part of the
17 may not be supported. [To understand ``intel_pstate`` it is necessary to know
21 For the processors supported by ``intel_pstate``, the P-state concept is broader
25 by ``intel_pstate`` internally follows the hardware specification (for details
30 ``intel_pstate`` maps its internal representation of P-states to frequencies too
32 practical for ``intel_pstate`` to supply the ``CPUFreq`` core with a table of
36 Since the hardware P-state selection interface used by ``intel_pstate`` is
38 CPUs. Consequently, if ``intel_pstate`` is in use, every ``CPUFreq`` policy
44 ``intel_pstate`` is not modular, so it cannot be unloaded, which means that the
55 ``intel_pstate`` can operate in three different modes: in the active mode with
63 This is the default operation mode of ``intel_pstate``. If it works in this
65 policies contains the string "intel_pstate".
78 ``intel_pstate`` is not a counterpart of the generic ``powersave`` governor
81 There are two P-state selection algorithms provided by ``intel_pstate`` in the
96 to avoid enabling it by passing the ``intel_pstate=no_hwp`` argument to the
99 If the HWP feature has been enabled, ``intel_pstate`` relies on the processor to
106 ``intel_pstate`` registers utilization update callbacks with the CPU scheduler
114 In this configuration ``intel_pstate`` will write 0 to the processor's
129 In this configuration ``intel_pstate`` will set the processor's
140 feature. It also is used by default with the ``intel_pstate=no_hwp`` argument
141 in the kernel command line. However, in this mode ``intel_pstate`` may refuse
143 ``intel_pstate`` will never refuse to work with any processor with the HWP
146 In this mode ``intel_pstate`` registers utilization update callbacks with the
189 This mode is used if the ``intel_pstate=passive`` argument is passed to the
190 kernel in the command line (it implies the ``intel_pstate=no_hwp`` setting too).
191 Like in the active mode without HWP support, in this mode ``intel_pstate`` may
201 While in this mode, ``intel_pstate`` can be used with all of the (generic)
209 the entire range of available P-states is exposed by ``intel_pstate`` to the
222 ``intel_pstate`` can be divided into two sub-ranges that correspond to
274 Unlike ``_PSS`` objects in the ACPI tables, ``intel_pstate`` always exposes
277 generally causes turbo P-states to be set more often when ``intel_pstate`` is
281 Moreover, since ``intel_pstate`` always knows what the real turbo threshold is
285 always should prevent ``intel_pstate`` from using them).
291 To handle a given processor ``intel_pstate`` requires a number of different
311 For this reason, there is a list of supported processors in ``intel_pstate`` and
316 ``intel_pstate``.]
325 ``intel_pstate`` exposes several global attributes (files) in ``sysfs`` to
327 ``/sys/devices/system/cpu/intel_pstate/`` directory and affect all CPUs.
329 Some of them are not present if the ``intel_pstate=per_cpu_perf_limits``
338 ``intel_pstate=per_cpu_perf_limits`` argument is present in the kernel
347 ``intel_pstate=per_cpu_perf_limits`` argument is present in the kernel
372 [Note that ``intel_pstate`` does not support the general ``boost``
382 This attribute is only present if ``intel_pstate`` works in the
430 :doc:`cpufreq` is special with ``intel_pstate`` as the current scaling driver
435 multiplier to the internal P-state representation used by ``intel_pstate``.
454 ``intel_pstate`` works in the `active mode <Active Mode_>`_:
457 List of P-state selection algorithms provided by ``intel_pstate``.
460 P-state selection algorithm provided by ``intel_pstate`` currently in
471 Additionally, the value of the ``scaling_driver`` attribute for ``intel_pstate``
473 "intel_pstate" (in the `active mode <Active Mode_>`_) or "intel_cpufreq" (in the
479 ``intel_pstate`` allows P-state limits to be set in two ways: with the help of
502 Additionally, if the ``intel_pstate=per_cpu_perf_limits`` command line argument
510 If ``intel_pstate`` works in the `active mode with the HWP feature enabled
513 user space to help ``intel_pstate`` to adjust the processor's internal P-state
544 ``intel_pstate`` vs ``acpi-cpufreq``
547 On the majority of systems supported by ``intel_pstate``, the ACPI tables
554 ``acpi-cpufreq`` scaling driver. On systems supported by ``intel_pstate``
561 be used by ``intel_pstate`` on the same system, with one exception: the whole
599 Apart from the above, ``acpi-cpufreq`` works like ``intel_pstate`` in the
604 Kernel Command Line Options for ``intel_pstate``
608 parameters to ``intel_pstate`` in order to enforce specific behavior of it. All
609 of them have to be prepended with the ``intel_pstate=`` prefix.
612 Do not register ``intel_pstate`` as the scaling driver even if the
616 Register ``intel_pstate`` in the `passive mode <Passive Mode_>`_ to
622 Register ``intel_pstate`` as the scaling driver instead of
631 ``intel_pstate`` and on platforms where the ``pcc-cpufreq`` scaling
639 Register ``intel_pstate`` as the scaling driver only if the
662 There are two static trace events that can be used for ``intel_pstate``
665 to ``intel_pstate``. Both of them are triggered by ``intel_pstate`` only if
678 If ``intel_pstate`` works in the `passive mode <Passive Mode_>`_, the
687 ``intel_pstate``. For example, to check how often the function to set a