diff options
Diffstat (limited to 'Documentation/admin-guide/pm')
| -rw-r--r-- | Documentation/admin-guide/pm/cpufreq.rst | 11 | ||||
| -rw-r--r-- | Documentation/admin-guide/pm/cpuidle.rst | 11 | ||||
| -rw-r--r-- | Documentation/admin-guide/pm/intel_pstate.rst | 8 |
3 files changed, 20 insertions, 10 deletions
diff --git a/Documentation/admin-guide/pm/cpufreq.rst b/Documentation/admin-guide/pm/cpufreq.rst index 368e612145d2..6adb7988e0eb 100644 --- a/Documentation/admin-guide/pm/cpufreq.rst +++ b/Documentation/admin-guide/pm/cpufreq.rst @@ -1,7 +1,6 @@ .. SPDX-License-Identifier: GPL-2.0 .. include:: <isonum.txt> -.. |struct cpufreq_policy| replace:: :c:type:`struct cpufreq_policy <cpufreq_policy>` .. |intel_pstate| replace:: :doc:`intel_pstate <intel_pstate>` ======================= @@ -92,16 +91,16 @@ control the P-state of multiple CPUs at the same time and writing to it affects all of those CPUs simultaneously. Sets of CPUs sharing hardware P-state control interfaces are represented by -``CPUFreq`` as |struct cpufreq_policy| objects. For consistency, -|struct cpufreq_policy| is also used when there is only one CPU in the given +``CPUFreq`` as struct cpufreq_policy objects. For consistency, +struct cpufreq_policy is also used when there is only one CPU in the given set. -The ``CPUFreq`` core maintains a pointer to a |struct cpufreq_policy| object for +The ``CPUFreq`` core maintains a pointer to a struct cpufreq_policy object for every CPU in the system, including CPUs that are currently offline. If multiple CPUs share the same hardware P-state control interface, all of the pointers -corresponding to them point to the same |struct cpufreq_policy| object. +corresponding to them point to the same struct cpufreq_policy object. -``CPUFreq`` uses |struct cpufreq_policy| as its basic data type and the design +``CPUFreq`` uses struct cpufreq_policy as its basic data type and the design of its user space interface is based on the policy concept. diff --git a/Documentation/admin-guide/pm/cpuidle.rst b/Documentation/admin-guide/pm/cpuidle.rst index a96a423e3779..37940a0584ec 100644 --- a/Documentation/admin-guide/pm/cpuidle.rst +++ b/Documentation/admin-guide/pm/cpuidle.rst @@ -528,6 +528,10 @@ object corresponding to it, as follows: Total number of times the hardware has been asked by the given CPU to enter this idle state. +``rejected`` + Total number of times a request to enter this idle state on the given + CPU was rejected. + The :file:`desc` and :file:`name` files both contain strings. The difference between them is that the name is expected to be more concise, while the description may be longer and it may contain white space or special characters. @@ -572,6 +576,11 @@ particular case. For these reasons, the only reliable way to find out how much time has been spent by the hardware in different idle states supported by it is to use idle state residency counters in the hardware, if available. +Generally, an interrupt received when trying to enter an idle state causes the +idle state entry request to be rejected, in which case the ``CPUIdle`` driver +may return an error code to indicate that this was the case. The :file:`usage` +and :file:`rejected` files report the number of times the given idle state +was entered successfully or rejected, respectively. .. _cpu-pm-qos: @@ -690,7 +699,7 @@ which of the two parameters is added to the kernel command line. In the instruction of the CPUs (which, as a rule, suspends the execution of the program and causes the hardware to attempt to enter the shallowest available idle state) for this purpose, and if ``idle=poll`` is used, idle CPUs will execute a -more or less ``lightweight'' sequence of instructions in a tight loop. [Note +more or less "lightweight" sequence of instructions in a tight loop. [Note that using ``idle=poll`` is somewhat drastic in many cases, as preventing idle CPUs from saving almost any energy at all may not be the only effect of it. For example, on Intel hardware it effectively prevents CPUs from using diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst index 7adef969ffee..5072e7064d13 100644 --- a/Documentation/admin-guide/pm/intel_pstate.rst +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -123,7 +123,9 @@ Energy-Performance Bias (EPB) knob (otherwise), which means that the processor's internal P-state selection logic is expected to focus entirely on performance. This will override the EPP/EPB setting coming from the ``sysfs`` interface -(see `Energy vs Performance Hints`_ below). +(see `Energy vs Performance Hints`_ below). Moreover, any attempts to change +the EPP/EPB to a value different from 0 ("performance") via ``sysfs`` in this +configuration will be rejected. Also, in this configuration the range of P-states available to the processor's internal P-state selection logic is always restricted to the upper boundary @@ -564,8 +566,8 @@ Energy-Performance Preference (EPP) knob (if supported) or its Energy-Performance Bias (EPB) knob. It is also possible to write a positive integer value between 0 to 255, if the EPP feature is present. If the EPP feature is not present, writing integer value to this attribute is not -supported. In this case, user can use - "/sys/devices/system/cpu/cpu*/power/energy_perf_bias" interface. +supported. In this case, user can use the +"/sys/devices/system/cpu/cpu*/power/energy_perf_bias" interface. [Note that tasks may by migrated from one CPU to another by the scheduler's load-balancing algorithm and if different energy vs performance hints are |