On Wed, 2022-02-16 at 19:44 +0100, Rafael J. Wysocki wrote: > On Mon, Feb 7, 2022 at 8:13 PM Srinivas Pandruvada > <srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote: > > > > Added documentation to configure uncore frequency limits in Intel > > Xeon processors. > > > > Signed-off-by: Srinivas Pandruvada > > <srinivas.pandruvada@xxxxxxxxxxxxxxx> > > --- > > Resent by adding linux-pm@xxxxxxxxxxxxxxx > > > > .../pm/intel_uncore_frequency_scaling.rst | 56 > > +++++++++++++++++++ > > .../admin-guide/pm/working-state.rst | 1 + > > 2 files changed, 57 insertions(+) > > create mode 100644 Documentation/admin- > > guide/pm/intel_uncore_frequency_scaling.rst > > > > diff --git a/Documentation/admin- > > guide/pm/intel_uncore_frequency_scaling.rst b/Documentation/admin- > > guide/pm/intel_uncore_frequency_scaling.rst > > new file mode 100644 > > index 000000000000..b3519560594b > > --- /dev/null > > +++ b/Documentation/admin- > > guide/pm/intel_uncore_frequency_scaling.rst > > @@ -0,0 +1,56 @@ > > +.. SPDX-License-Identifier: GPL-2.0 > > +.. include:: <isonum.txt> > > + > > +============================== > > +Intel Uncore Frequency Scaling > > +============================== > > + > > +:Copyright: |copy| 2022 Intel Corporation > > + > > +:Author: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> > > + > > +Introduction > > +=========================================== > > There are no other sections in this file, so can the section header > above be dropped? > Sure. Thanks, Srinivas > > + > > +Uncore can consume significant amount of power in Intel's Xeon > > servers based > > +on the workload characteristics. To optimize total power and > > improve overall > > +performance, SoC has an internal algorithm for scaling uncore > > frequency. These > > +algorithms monitor workload usage of uncore and set a desirable > > frequency. > > + > > +It is possible that users have different expectations of uncore > > performance and > > +want to have control over it. The objective is similar to set > > scaling min/max > > +frequencies using cpufreq sysfs to improve compute performance. > > Users may have > > +some latency sensitive workload where they do not want any change > > to uncore > > +frequency. Also, users may have workload which requires different > > core and > > +uncore performance at distinct phases and they want to use both > > cpufreq and > > +uncore scaling interface to distribute power and improve overall > > performance. > > + > > +To control uncore frequency, a sysfs interface is provided in the > > directory: > > +`/sys/devices/system/cpu/intel_uncore_frequency/`. > > + > > +There is one directory for each package and die combination as the > > scope of > > +uncore scaling control is per die in multiple dies/package SoC or > > per > > +package for single die per package SoC. The name represents the > > +scope of control. For example: 'package_00_die_00' is for package > > id 0 and > > +die 0 in it. > > + > > +Each package_*_die_* contains following attributes: > > + > > +``initial_max_freq_khz`` > > + Out of reset, this attribute represent the maximum possible > > frequency. > > + This is a read only attribute. If users adjust > > max_freq_khz, > > + they can always go back to maximum using the value from > > this attribute. > > + > > +``initial_min_freq_khz`` > > + Out of reset, this attribute represent the minimum possible > > frequency. > > + This is a read only attribute. If users adjust > > min_freq_khz, > > + they can always go back to minimum using the value from > > this attribute. > > + > > +``max_freq_khz`` > > + This attribute is used to set the maximum uncore frequency. > > + > > +``min_freq_khz`` > > + This attribute is used to set the minimum uncore frequency. > > + > > +``current_freq_khz`` > > + This attribute is used to get the current uncore frequency. > > diff --git a/Documentation/admin-guide/pm/working-state.rst > > b/Documentation/admin-guide/pm/working-state.rst > > index 5d2757e2de65..ee45887811ff 100644 > > --- a/Documentation/admin-guide/pm/working-state.rst > > +++ b/Documentation/admin-guide/pm/working-state.rst > > @@ -15,3 +15,4 @@ Working-State Power Management > > cpufreq_drivers > > intel_epb > > intel-speed-select > > + intel_uncore_frequency_scaling > > -- > > 2.34.1 > >
