admin-guide/pm/intel_pstate.rst

5 ``intel_pstate`` CPU Performance Scaling Driver
17 :doc:`CPU performance scaling subsystem <cpufreq>` in the Linux kernel
25 than just an operating frequency or an operating performance point (see the
30 uses frequencies for identifying operating performance points of CPUs and
58 active mode, it uses its own internal performance scaling governor algorithm or
61 a certain performance scaling algorithm.  Which of them will be in effect
88 active mode: ``powersave`` and ``performance``.  The way they both operate
94 Namely, if that option is set, the ``performance`` algorithm will be used by
117 HWP + ``performance``
121 Energy-Performance Preference (EPP) knob (if supported) or its
122 Energy-Performance Bias (EPB) knob (otherwise), which means that the processor's
123 internal P-state selection logic is expected to focus entirely on performance.
126 (see `Energy vs Performance Hints`_ below).  Moreover, any attempts to change
127 the EPP/EPB to a value different from 0 ("performance") via ``sysfs`` in this
138 Energy-Performance Preference (EPP) knob (if supported) or its
139 Energy-Performance Bias (EPB) knob (otherwise) to whatever value it was
142 internal P-state selection logic to be less performance-focused.
157 ``powersave`` or ``performance``, depending on the ``scaling_governor`` policy
162 ``performance``
187 every 10 ms.  Like in the ``performance`` case, the hardware configuration
249 performance scaling control for that core and put it into turbo P-states of its
292 used relative to ACPI-based CPU performance scaling (see `below <acpi-cpufreq_>`_
347 	maximum supported performance level (the highest supported `turbo
356 	maximum supported performance level (the highest supported `turbo
400 	of this mechanism is to improve performance).
517     effective performance depends on whether the platform supports per core
518     P-states, hyper-threading is enabled and on current performance requests
520     effective performance can be more than the policy limits set on a CPU, if
521     other CPUs are requesting higher performance at that moment. Even with per
523     is requesting higher performance, the other siblings will get higher
524     performance than their policy limits.
540 Energy vs Performance Hints
545 processor's internal P-state selection logic by focusing it on performance or on
550 	Current value of the energy vs performance hint for the given policy
559 	They represent different energy vs performance hints and should be
565 Energy-Performance Preference (EPP) knob (if supported) or its
566 Energy-Performance Bias (EPB) knob. It is also possible to write a positive
573 load-balancing algorithm and if different energy vs performance hints are
575 issues it is better to set the same energy vs performance hint for all CPUs
585 that can be used for CPU performance scaling (refer to the ACPI specification
591 the ``acpi-cpufreq`` driver uses the same hardware CPU performance scaling
613 ``performance``.
681 	Take ACPI ``_PPC`` performance limits into account.
684 	Description Table) is set to "Enterprise Server" or "Performance
756 .. [1] Kristen Accardi, *Balancing Power and Performance in the Linux Kernel*,