CC: linux-pm, please! On Mon, Feb 7, 2022 at 7:21 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> > --- > .../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 > +=========================================== > + > +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 >
