From 1f93a7dfd1f8d5ff7a5c53246c7534fe2332d6f4 Mon Sep 17 00:00:00 2001 From: hc <hc@nodka.com> Date: Mon, 11 Dec 2023 02:46:07 +0000 Subject: [PATCH] add audio --- kernel/Documentation/admin-guide/pm/cpufreq.rst | 37 ++++++++++++++++++++++--------------- 1 files changed, 22 insertions(+), 15 deletions(-) diff --git a/kernel/Documentation/admin-guide/pm/cpufreq.rst b/kernel/Documentation/admin-guide/pm/cpufreq.rst index 1f563da..19c50f3 100644 --- a/kernel/Documentation/admin-guide/pm/cpufreq.rst +++ b/kernel/Documentation/admin-guide/pm/cpufreq.rst @@ -1,13 +1,16 @@ -.. |struct cpufreq_policy| replace:: :c:type:`struct cpufreq_policy <cpufreq_policy>` +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + .. |intel_pstate| replace:: :doc:`intel_pstate <intel_pstate>` ======================= CPU Performance Scaling ======================= -:: +:Copyright: |copy| 2017 Intel Corporation - Copyright (c) 2017 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com> +:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com> + The Concept of CPU Performance Scaling ====================================== @@ -88,16 +91,16 @@ 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. @@ -143,14 +146,14 @@ The next major initialization step for a new policy object is to attach a scaling governor to it (to begin with, that is the default scaling governor -determined by the kernel configuration, but it may be changed later -via ``sysfs``). First, a pointer to the new policy object is passed to the -governor's ``->init()`` callback which is expected to initialize all of the +determined by the kernel command line or configuration, but it may be changed +later via ``sysfs``). First, a pointer to the new policy object is passed to +the governor's ``->init()`` callback which is expected to initialize all of the data structures necessary to handle the given policy and, possibly, to add a governor ``sysfs`` interface to it. Next, the governor is started by invoking its ``->start()`` callback. -That callback it expected to register per-CPU utilization update callbacks for +That callback is expected to register per-CPU utilization update callbacks for all of the online CPUs belonging to the given policy with the CPU scheduler. The utilization update callbacks will be invoked by the CPU scheduler on important events, like task enqueue and dequeue, on every iteration of the @@ -396,8 +399,8 @@ the allowed maximum (that is, the ``scaling_max_freq`` policy limit). In turn, if it is invoked by the CFS scheduling class, the governor will use the Per-Entity Load Tracking (PELT) metric for the root control group of the -given CPU as the CPU utilization estimate (see the `Per-entity load tracking`_ -LWN.net article for a description of the PELT mechanism). Then, the new +given CPU as the CPU utilization estimate (see the *Per-entity load tracking* +LWN.net article [1]_ for a description of the PELT mechanism). Then, the new CPU frequency to apply is computed in accordance with the formula f = 1.25 * ``f_0`` * ``util`` / ``max`` @@ -756,4 +759,8 @@ :c:macro:`CONFIG_X86_ACPI_CPUFREQ_CPB` configuration option is set. -.. _Per-entity load tracking: https://lwn.net/Articles/531853/ +References +========== + +.. [1] Jonathan Corbet, *Per-entity load tracking*, + https://lwn.net/Articles/531853/ -- Gitblit v1.6.2