GEOPM_CXX_MAN_AGENT(3)

NAME
GEOPM_CXX_MAN_Agent - GEOPM agent plugin interface

NAMESPACES

The Agent class and the agent_factory() function are members of the namespace geopm, but the full names, geopm::Agent and geopm::agent_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::pair, std::string, std::map, and std::function, to enable better rendering of this manual.

SYNOPSIS

#include <geopm/Agent.hpp>

Link with -lgeopm

PluginFactory<Agent> &agent_factory(void);
virtual void Agent::init(int level, const vector<int> &fan_in, bool is_level_root) = 0;
virtual void Agent::validate_policy(vector<double> &policy) const = 0;
virtual void Agent::split_policy(const vector<double> &in_policy,
                                 vector<vector<double> >& out_policy) = 0;
virtual bool Agent::do_send_policy(void) const = 0;
virtual void Agent::aggregate_sample(const vector<vector<double> > &in_sample,
                                     vector<double> &out_sample) = 0;
virtual bool Agent::do_send_sample(void) const = 0;
virtual void Agent::adjust_platform(const vector<double> &in_policy) = 0;
virtual bool Agent::do_write_batch(void) const = 0;
virtual void Agent::sample_platform(vector<double> &out_sample) = 0;
virtual void Agent::wait(void) = 0;
virtual vector<pair<string, string> > Agent::report_header(void) const = 0;
virtual vector<pair<string, string> > Agent::report_host(void) const = 0;
virtual map<uint64_t, vector<pair<string, string> > > Agent::report_region(void) const = 0;
virtual vector<string> Agent::trace_names(void) const = 0;
virtual vector<function<string(double)> > Agent::trace_formats(void) const;
virtual void Agent::trace_values(vector<double> &values) = 0;
virtual void Agent::enforce_policy(const vector<double> &policy) const = 0;
static int Agent::num_policy(const map<string, string> &dictionary);
static int Agent::num_policy(const string &agent_name);
static int Agent::num_sample(const map<string, string> &dictionary);
static int Agent::num_sample(const string &agent_name);
static vector<string> Agent::policy_names(const map<string, string> &dictionary);
static vector<string> Agent::policy_names(const string &agent_name);
static vector<string> Agent::sample_names(const map<string, string> &dictionary);
static vector<string> Agent::sample_names(const string &agent_name);
static map<string, string> Agent::make_dictionary(const vector<string> &policy_names,
                                                  const vector<string> &sample_names);
static void Agent::aggregate_sample(const vector<vector<double> > &in_sample,
                                    const vector<function<double(const vector<double>&)> > &agg_func,
                                    vector<double> &out_sample);

DESCRIPTION

The Agent class is an abstract pure virtual class that defines the fundamental procedures executed by the GEOPM runtime. In general, the Agent is responsible for making decisions about how and what control the runtime should exert based on readings of system values. By default the geopm_agent_monitor(7) is used, but other agents can be selected with the --geopm-agent command line option to the geopmlaunch(1) or GEOPM_AGENT environment variable. Exactly one agent type is used during each execution of the GEOPM runtime.

The geopm::PluginFactory(3) man page gives a general overview of concepts related to extending GEOPM through plugins. Please refer to that overview as an introduction before implementing an Agent plugin.

A single process (or application thread) on each compute node utilized by an application running with GEOPM creates a Controller object and each of these objects creates one or more Agent objects. The Agent objects are related to each other through a balanced tree of bi-directional communication. The "leaf" Agent objects are defined to have no children and one parent. The "tree" Agent objects defined to have many children and one Agent as the parent. The "root" Agent objects are defined to have many children and a static policy as the parent. Note that in some cases (e.g. a single node job execution) a "tree" Agent may not be involved at all. The Agent::init() method is called by the Controller prior to all other Agent methods. The parameters passed by the Controller in this call define the geometry of the Agent tree and where the particular Agent object falls in the tree. See detailed description of Agent::init() below for more information about the tree structure.

All Controllers create an Agent object to execute level 0, or "leaf" responsibilities. The leaf responsibilities include monitoring signals and deriving samples to send to their parent Agents at level 1 in the tree. Additionally a leaf Agent must interpret policies received from their parent agent at level 1 and set controls which reflect the policy. Some of the Controller objects will create Agent objects to execute non-zero level, or "tree" responsibilities. These non-zero level Agent objects are responsible for aggregating samples from child agents to send to parent agents and splitting policy values from parent agents to send to child agents. Note that the Agent running at the root of the tree uses the same policy/sample interface to interact with the resource manager.

The Agent class is designed to read signals and write controls for the hardware and application using the geopm::PlatformIO(3) interface. Please see the manual for details about how the PlatformIO abstraction enables access to hardware capabilities, extension of Agent algorithms to new hardware architectures, a mapping of application behavior to hardware domains, and code reuse of I/O implementations by different Agent classes.

FACTORY ACCESSOR

•   agent_factory(): This method returns the singleton accessor for the Agent factory. 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 Agents will be attempted. For more information see geopm::PluginFactory(3).

CLASS METHODS

•   init(): The init() method is the first method that will be called and provides contextual information for the Agent about the communication tree geometry and where in the tree the Agent resides. The communication tree that connects the Agent objects is a balanced tree. The level is the minimum number of edges between self and any leaf Agent. Only when level is zero will the sample_platform() and adjust_platform() methods be called. If the level is zero then the init() method should push all signals and controls for PlatformIO(3). The fan_in is a vector indexed by level that describes the number of siblings that an Agent at level has which share a parent. The figure below represents a tree with fan_in == {4,3,2} where each Agent is signified by a digit that is equal to the level. Note that this example supports 24 compute nodes. The is_level_root parameter is true for one child of each parent and only if this parameter is true will the controller call the ascend() or descend() methods of the object.

                                    (3)
                         ___________/ \____________
                        /                          \
                   __ (2)                         _(2)__
           _______/  /   \_____             _____/    | \_______
          /         |          \           /          |         \
        (1)        (1)        (1)         (1)        (1)        (1)
       -- --      -- --      -- --       -- --      -- --      -- --
      /  |  \    /  |  \    /  |  \     /  |  \    /  |  \    /  |  \
    (0)(0|0)(0)(0)(0|0)(0)(0)(0|0)(0) (0)(0|0)(0)(0)(0|0)(0)(0)(0|0)(0)

•   validate_policy(): Called by user of Agent class to validate incoming policy values and replace NaNs with defaults. If a value of policy is not NaN but the value is not supported by the Agent the method will throw a geopm::Exception with error code GEOPM_ERROR_INVALID.

•   split_policy(): Split policy for children at next level down the tree. The in_policy is an input vector of policy values from the parent. The out_policy is an output vector of policies to be sent to each child.

•   do_send_policy(): Used to indicate to the Controller whether to send the output from split_policy() down the tree to the Agent's children. Returns true if the policy has been updated since the last call.

•   aggregate_sample(): Aggregate samples from children for the next level up the tree. The in_sample parameter is a vector of sample vectors, one sample vector from each child. The samples from a given index in the input vectors are transformed to a single value at the same index in the output. The out_sample is an output vector of aggregated sample values to be sent up to the parent.

•   do_send_sample(): Used to indicate to the Controller whether to send the output from aggregate_sample() up the tree to the Agent's parent. Returns true if any samples have been updated since the last call.

•   adjust_platform(): Adjust the platform settings based on the policy from above. Settings for each control are in the in_policy.

•   do_write_batch(): Used to indicate to the Controller whether to call PlatformIO::write_batch() to enact new control values on the platform. Returns true if any control values have been updated since the last call.

•   sample_platform(): Read signals from the platform and interpret/aggregate these signals to create a sample which can be sent up the tree. The out_sample parameter is an output vector of agent specific sample values to be sent up the tree. Returns true if the sample has been updated since the last call.

•   wait(): Called to wait for the sample period to elapse. This controls the cadence of the Controller main loop.

•   report_header(): Custom fields that will be added to the report header when this agent is used. To be consistent with the rest of the header, the keys should be title case, e.g. "Agent Header Name"; they must not contain the colon character ':'. Care must be taken not to add keys that conflict with default header keys, like names that start with "Start Time", "Profile", "Agent" or "Policy".

•   report_host(): Custom fields for the Host section of the report. To be consistent with the rest of this section, the keys should have the first letter capitalized, e.g. "Final freq map"; they must not contain the colon character ':'. Care must be taken not to add keys that conflict with default host keys, like names that start with "Region", "Epoch Totals" or "Application Totals".

•   report_region(): Custom fields for each region in the report. To be consistent with the rest of the region report, the string keys that will appear at the start of each line should be all lower case with words separated by hyphens and followed by the units if applicable, e.g "package-energy (joules)". The field name must not contain the colon character ':'. Care must be taken not to add keys that conflict with the default region keys, like names that start with "runtime", "sync-runtime", "package-energy", "dram-energy", "power", "frequency", "network-time", or "count".

•   trace_names(): Column headers to be added to the trace. These will be automatically converted to lower case. The header names must not contain the pipe character '|' or whitespace.

•   trace_formats(): Returns format string for each column added to the trace

•   trace_values(): Called by Controller to get latest values to be added to the trace.

•   enforce_policy(): Enforce the policy one time with PlatformIO::write_control(). Called to enforce static policies in the absence of a Controller.

•   num_policy(): Used to look up the number of values in the policy vector sent down the tree for a specific type of Agent. This should be called with the dictionary returned by agent_factory().dictionary(agent_name) for the Agent of interest. Also has an overloaded version which takes the agent_name. Note this is a static helper function.

•   num_sample(): Used to look up the number of values in the sample vector sent up the tree for a specific type of Agent. This should be called with the dictionary returned by agent_factory().dictionary(agent_name) for the Agent of interest. Also has an overloaded version which takes the agent_name. Note this is a static helper function.

•   policy_names(): Used to look up the names of values in the policy vector sent down the tree for a specific type of Agent. This should be called with the dictionary returned by agent_factory().dictionary(agent_name) for the Agent of interest. Also has an overloaded version which takes the agent_name. Note this is a static helper function.

•   sample_names(): Used to look up the names of values in the sample vector sent up the tree for a specific of Agent. This should be called with the dictionary returned by agent_factory().dictionary(agent_name) for the Agent of interest. Also has an overloaded version which takes the agent_name. Note this is a static helper function.

•   make_dictionary(): Used to create a correctly formatted dictionary for an Agent at the time the Agent is registered with the factory. Concrete Agent` classes may provide policy_names() and sample_names() methods to provide the vectors to be passed to this method. Note this is a static helper function.

•   aggregate_sample(): Generically aggregate a vector of samples given a vector of aggregation functions. This helper method applies a different aggregation function to each sample element while aggregating across child samples. The in_sample parameter is an input vector over children of the sample vector received from each child. The agg_func is an input vector over agent samples of the aggregation function that is applied. The out_sample is an output sample vector resulting from the applying the aggregation across child samples. Note this is a static helper function.

ERRORS

All functions described on this man page throw geopm::Exception(3) on error.

EXAMPLE

Please see the Agent tutorial for more information. This code is located in the GEOPM source under tutorial/agent.

SEE ALSO

geopm(7)

AUTHOR
Christopher Cantalupo, Brad Geltz, Konstantin Rebrov

COPYRIGHT
2015 - 2023, Intel Corporation. All rights reserved.