diff options
Diffstat (limited to 'Documentation/admin-guide/pm')
| -rw-r--r-- | Documentation/admin-guide/pm/cpuidle.rst | 20 | ||||
| -rw-r--r-- | Documentation/admin-guide/pm/intel_pstate.rst | 32 |
2 files changed, 28 insertions, 24 deletions
diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst index 5605cc6f9560..a96a423e3779 100644 --- a/Documentation/admin-guide/pm/cpuidle.rst +++ b/Documentation/admin-guide/pm/cpuidle.rst @@ -159,17 +159,15 @@ governor uses that information depends on what algorithm is implemented by it and that is the primary reason for having more than one governor in the ``CPUIdle`` subsystem. -There are three ``CPUIdle`` governors available, ``menu``, `TEO <teo-gov_>`_ -and ``ladder``. Which of them is used by default depends on the configuration -of the kernel and in particular on whether or not the scheduler tick can be -`stopped by the idle loop <idle-cpus-and-tick_>`_. It is possible to change the -governor at run time if the ``cpuidle_sysfs_switch`` command line parameter has -been passed to the kernel, but that is not safe in general, so it should not be -done on production systems (that may change in the future, though). The name of -the ``CPUIdle`` governor currently used by the kernel can be read from the -:file:`current_governor_ro` (or :file:`current_governor` if -``cpuidle_sysfs_switch`` is present in the kernel command line) file under -:file:`/sys/devices/system/cpu/cpuidle/` in ``sysfs``. +There are four ``CPUIdle`` governors available, ``menu``, `TEO <teo-gov_>`_, +``ladder`` and ``haltpoll``. Which of them is used by default depends on the +configuration of the kernel and in particular on whether or not the scheduler +tick can be `stopped by the idle loop <idle-cpus-and-tick_>`_. Available +governors can be read from the :file:`available_governors`, and the governor +can be changed at runtime. The name of the ``CPUIdle`` governor currently +used by the kernel can be read from the :file:`current_governor_ro` or +:file:`current_governor` file under :file:`/sys/devices/system/cpu/cpuidle/` +in ``sysfs``. Which ``CPUIdle`` driver is used, on the other hand, usually depends on the platform the kernel is running on, but there are platforms with more than one diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst index ad392f3aee06..39d80bc29ccd 100644 --- a/Documentation/admin-guide/pm/intel_pstate.rst +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -62,9 +62,10 @@ on the capabilities of the processor. Active Mode ----------- -This is the default operation mode of ``intel_pstate``. If it works in this -mode, the ``scaling_driver`` policy attribute in ``sysfs`` for all ``CPUFreq`` -policies contains the string "intel_pstate". +This is the default operation mode of ``intel_pstate`` for processors with +hardware-managed P-states (HWP) support. If it works in this mode, the +``scaling_driver`` policy attribute in ``sysfs`` for all ``CPUFreq`` policies +contains the string "intel_pstate". In this mode the driver bypasses the scaling governors layer of ``CPUFreq`` and provides its own scaling algorithms for P-state selection. Those algorithms @@ -138,12 +139,13 @@ internal P-state selection logic to be less performance-focused. Active Mode Without HWP ~~~~~~~~~~~~~~~~~~~~~~~ -This is the default operation mode for processors that do not support the HWP -feature. It also is used by default with the ``intel_pstate=no_hwp`` argument -in the kernel command line. However, in this mode ``intel_pstate`` may refuse -to work with the given processor if it does not recognize it. [Note that -``intel_pstate`` will never refuse to work with any processor with the HWP -feature enabled.] +This operation mode is optional for processors that do not support the HWP +feature or when the ``intel_pstate=no_hwp`` argument is passed to the kernel in +the command line. The active mode is used in those cases if the +``intel_pstate=active`` argument is passed to the kernel in the command line. +In this mode ``intel_pstate`` may refuse to work with processors that are not +recognized by it. [Note that ``intel_pstate`` will never refuse to work with +any processor with the HWP feature enabled.] In this mode ``intel_pstate`` registers utilization update callbacks with the CPU scheduler in order to run a P-state selection algorithm, either @@ -188,10 +190,14 @@ is not set. Passive Mode ------------ -This mode is used if the ``intel_pstate=passive`` argument is passed to the -kernel in the command line (it implies the ``intel_pstate=no_hwp`` setting too). -Like in the active mode without HWP support, in this mode ``intel_pstate`` may -refuse to work with the given processor if it does not recognize it. +This is the default operation mode of ``intel_pstate`` for processors without +hardware-managed P-states (HWP) support. It is always used if the +``intel_pstate=passive`` argument is passed to the kernel in the command line +regardless of whether or not the given processor supports HWP. [Note that the +``intel_pstate=no_hwp`` setting implies ``intel_pstate=passive`` if it is used +without ``intel_pstate=active``.] Like in the active mode without HWP support, +in this mode ``intel_pstate`` may refuse to work with processors that are not +recognized by it. If the driver works in this mode, the ``scaling_driver`` policy attribute in ``sysfs`` for all ``CPUFreq`` policies contains the string "intel_cpufreq". |