mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-05 10:04:12 +08:00
7973b799db
Add an SPDX license tag and a copyright notice to the intel_epb.rst file under Documentation/admin-quide/pm. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
42 lines
1.6 KiB
ReStructuredText
42 lines
1.6 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
|
|
.. include:: <isonum.txt>
|
|
|
|
======================================
|
|
Intel Performance and Energy Bias Hint
|
|
======================================
|
|
|
|
:Copyright: |copy| 2019 Intel Corporation
|
|
|
|
:Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
|
|
|
|
|
|
.. kernel-doc:: arch/x86/kernel/cpu/intel_epb.c
|
|
:doc: overview
|
|
|
|
Intel Performance and Energy Bias Attribute in ``sysfs``
|
|
========================================================
|
|
|
|
The Intel Performance and Energy Bias Hint (EPB) value for a given (logical) CPU
|
|
can be checked or updated through a ``sysfs`` attribute (file) under
|
|
:file:`/sys/devices/system/cpu/cpu<N>/power/`, where the CPU number ``<N>``
|
|
is allocated at the system initialization time:
|
|
|
|
``energy_perf_bias``
|
|
Shows the current EPB value for the CPU in a sliding scale 0 - 15, where
|
|
a value of 0 corresponds to a hint preference for highest performance
|
|
and a value of 15 corresponds to the maximum energy savings.
|
|
|
|
In order to update the EPB value for the CPU, this attribute can be
|
|
written to, either with a number in the 0 - 15 sliding scale above, or
|
|
with one of the strings: "performance", "balance-performance", "normal",
|
|
"balance-power", "power" that represent values reflected by their
|
|
meaning.
|
|
|
|
This attribute is present for all online CPUs supporting the EPB
|
|
feature.
|
|
|
|
Note that while the EPB interface to the processor is defined at the logical CPU
|
|
level, the physical register backing it may be shared by multiple CPUs (for
|
|
example, SMT siblings or cores in one package). For this reason, updating the
|
|
EPB value for one CPU may cause the EPB values for other CPUs to change.
|