geopm::IOGroup(3) – provides system values and settings

Namespaces

The IOGroup class and the iogroup_factory() singleton accessor function are members of the namespace geopm, but the full names, geopm::IOGroup and geopm::iogroup_factory(), have been abbreviated in this manual. Similarly, the std:: namespace specifier has been omitted from the interface definitions for the following standard types: std::vector, std::string, std::set, and std::function, to enable better rendering of this manual.

Synopsis

#include <geopm/IOGroup.hpp>

Link with -lgeopmd

PluginFactory<IOGroup> &iogroup_factory(void);

static vector<string> IOGroup::iogroup_names(void);

static unique_ptr<IOGroup> IOGroup::make_unique(const string &iogroup_name);

set<string> IOGroup::signal_names(void) const;

set<string> IOGroup::control_names(void) const;

bool IOGroup::is_valid_signal(const string &signal_name) const;

bool IOGroup::is_valid_control(const string &control_name) const;

int IOGroup::signal_domain_type(const string &signal_name) const;

int IOGroup::control_domain_type(const string &control_name) const;

int IOGroup::push_signal(const string &signal_name,
                         int domain_type,
                         int domain_idx);

int IOGroup::push_control(const string &control_name,
                          int domain_type,
                          int domain_idx);

void IOGroup::read_batch(void);

void IOGroup::write_batch(void);

double IOGroup::sample(int sample_idx);

void IOGroup::adjust(int control_idx,
                     double setting);

double IOGroup::read_signal(const string &signal_name,
                            int domain_type,
                            int domain_idx);

void IOGroup::write_control(const string &control_name,
                            int domain_type,
                            int domain_idx,
                            double setting);

void IOGroup::save_control(void);

void IOGroup::restore_control(void);

function<double(const vector<double> &)> IOGroup::agg_function(const string &signal_name) const;

function<string(double)> IOGroup::format_function(const string &signal_name) const;

string IOGroup::signal_description(const string &signal_name) const;

string IOGroup::control_description(const string &control_name) const;

int IOGroup::signal_behavior(const string &signal_name) const;

void IOGroup::save_control(const string &save_path);

void IOGroup::restore_control(const string &save_path);

static IOGroup::m_units_e IOGroup::string_to_units(const string &str);

static string IOGroup::units_to_string(int);

static IOGroup::m_signal_behavior_e IOGroup::string_to_behavior(const string &str);

Description

The IOGroup class is an abstract pure virtual class that defines the high level interface employed by plugins for sample input and control output. An Agent, provided by the geopm::Agent(3) class, will define one or more IOGroups in order to:

Acquire the necessary sample data required for the Agent.
Perform the necessary control operations as specified by the Agent.

Classes may derive from the IOGroup class in order to provide an Agent with additional sample data or control hooks other than what is provided by GEOPM. The pure virtual methods in this interface must be implemented by every IOGroup. If an IOGroup provides only signals, the methods related to controls can have empty or degenerate implementations; the reverse is also true if an IOGroup only provides controls. In these cases, ensure that is_valid_signal() or is_valid_control() returns false as appropriate, and that signal_names() or control_names() returns an empty set. GEOPM provides a number of built-in IOGroups for the most common usages. The list of built-in IOGroups is as follows:

CpuinfoIOGroup: Provides constants for CPU frequency limits. Discussed in geopm::CpuinfoIOGroup(3).
MSRIOGroup: Provides signals and controls based on MSRs. Discussed in geopm::MSRIOGroup(3).
ProfileIOGroup: Provides signals from the application. Discussed in geopm::ProfileIOGroup(3).
TimeIOGroup: Provides a signal for the current time. Discussed in geopm::TimeIOGroup(3).

The APIs discussed in geopm::PlatformIO(3) with regard to signals and controls are ultimately fulfilled by the individual IOGroups that implement this interface.

If multiple IOGroups define signals or controls that have the same name, the IOGroup that is loaded last will override the others. This effectively means that the last loaded IOGroup that defines a signal or control will fulfill requests for that signal or control.

Terms

Below are some definitions of terms that are used to describe different parts of the IOGroup interface. Understanding these terms will help to interpret the documentation about how to extend IOGroups.

signal: Named parameter in SI units that can be measured.
control : Named parameter in SI units that can be set.
domain: The discrete component within a compute node where a signal or control is applicable. For more information see geopm::PlatformTopo(3).

Factory Accessor

iogroup_factory(): This method returns the singleton accessor for the IOGroupFactory. Calling this method will create the factory if it does not already exist. If this method is creating the factory, loading of the built-in IOGroups will be attempted. For more information see geopm::PlatformIO(3) and/or geopm::PluginFactory(3).

Class Methods

iogroup_names(): Provides the list of the IOGroups that are available in the factory.
make_unique(): Returns a unique_ptr to a new IOGroup object, uses the IOGroup factory to create an object of that type.
signal_names(): Provides the list of all signals provided by the IOGroup. The set of strings that are returned can be passed as a signal_name to all of the IOGroup methods that accept a signal_name as an input parameter.
control_names(): Provides the list of all controls provided by the IOGroup. The set of strings that are returned can be passed as a control_name to all of the IOGroup methods that accept a control_name as an input parameter.
is_valid_signal(): Tests if the signal_name refers to a signal supported by the IOGroup.
is_valid_control(): Test if the control_name refers to a control supported by the IOGroup.
signal_domain_type(): Query the domain for a named signal.
control_domain_type(): Query the domain for a named control.
push_signal(): Add a signal to the list of signals that is read by read_batch() and sampled by sample(). This method should return a unique index for each signal that can be utilized when calling sample().
push_control(): Add a control to the list of controls that is written by write_batch() and configured with adjust(). This method should return a unique index for each control that can be utilized when calling control().
read_batch(): Read all pushed signals from the platform so that the next call to sample() will reflect the updated data. The intention is that read_batch() will read the all of the IOGroup‘s signals into memory once per call.
write_batch(): Write all of the pushed controls so that values previously given to adjust() are written to the platform.
sample(): Retrieve a signal value from the data read by the last call to read_batch() for a particular signal previously pushed with push_signal().
adjust(): Adjust a setting for a particular control that was previously pushed with push_control(). This adjustment will be written to the platform on the next call to write_batch().
read_signal(): Read from platform and interpret into SI units a signal given its name and domain. Does not modify the values stored by calling read_batch().
write_control(): Interpret the setting and write setting to the platform. Does not modify the values stored by calling adjust().
save_control(): Save the state of all controls so that any subsequent changes made through the IOGroup can be undone with a call to the restore() method. Also has an overloaded version which takes the save_path.
restore_control(): Restore all controls to values recorded in previous call to the save() method. Also has an overloaded version which takes the save_path.
agg_function(): Returns a function that should be used when aggregating a signal of the type signal_name. For more information see geopm::Agg(3).
format_function(): Returns a function that can be used to convert a signal of the type signal_name into a human readable string representation.
signal_description(): Returns a description of the signal. This string can be used by tools to generate help text for users of the IOGroup.
control_description(): Returns a description of the control. This string can be used by tools to generate help text for users of the IOGroup.
signal_behavior(): Returns one of the IOGroup::signal_behavior_e values which describes about how a signal will change as a function of time. This can be used when generating reports to decide how to summarize a signal’s value for the entire application run.
string_to_units(): Convert a string to the corresponding m_units_e value
units_to_string(): Convert the m_units_e value to the corresponding string.
string_to_behavior(): Convert a string to the corresponding m_signal_behavior_e value

Example

Please see the GEOPM IOGroup tutorial for more information. That code is located in the GEOPM source under tutorial/iogroup.

Further documentation for this module can be found in the doxygen page.