src/doc/power_thermal_model.doxygen - amd/gem5 - Git at Google


            
            # Copyright (c) 2016 ARM Limited

            
            # All rights reserved

            
            #

            
            # The license below extends only to copyright in the software and shall

            
            # not be construed as granting a license to any other intellectual

            
            # property including but not limited to intellectual property relating

            
            # to a hardware implementation of the functionality of the software

            
            # licensed hereunder.  You may use the software subject to the license

            
            # terms below provided that you ensure that this notice is replicated

            
            # unmodified and in its entirety in all distributions of the software,

            
            # modified or unmodified, in source code or in binary form.

            
            #

            
            # Redistribution and use in source and binary forms, with or without

            
            # modification, are permitted provided that the following conditions are

            
            # met: redistributions of source code must retain the above copyright

            
            # notice, this list of conditions and the following disclaimer;

            
            # redistributions in binary form must reproduce the above copyright

            
            # notice, this list of conditions and the following disclaimer in the

            
            # documentation and/or other materials provided with the distribution;

            
            # neither the name of the copyright holders nor the names of its

            
            # contributors may be used to endorse or promote products derived from

            
            # this software without specific prior written permission.

            
            #

            
            # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

            
            # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

            
            # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

            
            # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

            
            # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

            
            # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

            
            # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

            
            # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

            
            # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

            
            # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

            
            # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

            
            #

            
            # Author: David Guillen Fandos


            /*! \page gem5PowerModel Gem5 Power & Thermal model


              \tableofcontents


              This document gives an overview of the power and thermal modelling

            
              infrastructure in Gem5. The purpose is to give a high level view of

            
              all the pieces involved and how they interact with each other and

            
              the simulator.


              \section gem5_PM_CD Class overview


              Classes involved in the power model are:


                - PowerModel: Represents a power model for a hardware component.


                - PowerModelState: Represents a power model for a hardware component

            
                  in a certain power state. It is an abstract class that defines an

            
                  interface that must be implemented for each model.


                - MathExprPowerModel: Simple implementation of PowerModelState that

            
                  assumes that power can be modeled using a simple power


              Classes involved in the thermal model are:


                - ThermalModel: Contains the system thermal model logic and state.

            
                  It performs the power query and temperature update. It also enables

            
                  gem5 to query for temperature (for OS reporting).


                - ThermalDomain: Represents an entity that generates heat. It's

            
                  essentially a group of SimObjects grouped under a SubSystem component

            
                  that have its own thermal behaviour.


                - ThermalNode: Represents a node in the thermal circuital equivalent.

            
                  The node has a temperature and interacts with other nodes through

            
                  connections (thermal resistors and capacitors).


                - ThermalReference: Temperature reference for the thermal model

            
                  (essentially a thermal node with a fixed temperature), can be used

            
                  to model air or any other constant temperature domains.


                - ThermalEntity: A thermal component that connects two thermal nodes

            
                  and models a thermal impedance between them. This class is just an

            
                  abstract interface.


                - ThermalResistor: Implements ThermalEntity to model a thermal resistance

            
                  between the two nodes it connects. Thermal resistances model the

            
                  capacity of a material to transfer heat (units in K/W).


                - ThermalCapacitor. Implements ThermalEntity to model a thermal

            
                  capacitance. Thermal capacitors are used to model material's thermal

            
                  capacitance, this is, the ability to change a certain material

            
                  temperature (units in J/K).


              \section gem5_thermal Thermal model


              The thermal model works by creating a circuital equivalent of the

            
              simulated platform. Each node in the circuit has a temperature (as

            
              voltage equivalent) and power flows between nodes (as current in a

            
              circuit).


              To build this equivalent temperature model the platform is required

            
              to group the power actors (any component that has a power model)

            
              under SubSystems and attach ThermalDomains to those subsystems.

            
              Other components might also be created (like ThermalReferences) and

            
              connected all together by creating thermal entities (capacitors and

            
              resistors).


              Last step to conclude the thermal model is to create the ThermalModel

            
              instance itself and attach all the instances used to it, so it can

            
              properly update them at runtime. Only one thermal model instance is

            
              supported right now and it will automatically report temperature when

            
              appropriate (ie. platform sensor devices).


              \section gem5_power Power model


              Every ClockedObject has a power model associated. If this power model is

            
              non-null power will be calculated at every stats dump (although it might

            
              be possible to force power evaluation at any other point, if the power

            
              model uses the stats, it is a good idea to keep both events in sync).

            
              The definition of a power model is quite vague in the sense that it is

            
              as flexible as users want it to be. The only enforced contraints so far

            
              is the fact that a power model has several power state models, one for

            
              each possible power state for that hardware block. When it comes to compute

            
              power consumption the power is just the weighted average of each power model.


              A power state model is essentially an interface that allows us to define two

            
              power functions for dynamic and static. As an example implementation a class

            
              called MathExprPowerModel has been provided. This implementation allows the

            
              user to define a power model as an equation involving several statistics.

            
              There's also some automatic (or "magic") variables such as "temp", which

            
              reports temperature.

            
            */
	# Copyright (c) 2016 ARM Limited
	# All rights reserved
	#
	# The license below extends only to copyright in the software and shall
	# not be construed as granting a license to any other intellectual
	# property including but not limited to intellectual property relating
	# to a hardware implementation of the functionality of the software
	# licensed hereunder. You may use the software subject to the license
	# terms below provided that you ensure that this notice is replicated
	# unmodified and in its entirety in all distributions of the software,
	# modified or unmodified, in source code or in binary form.
	#
	# Redistribution and use in source and binary forms, with or without
	# modification, are permitted provided that the following conditions are
	# met: redistributions of source code must retain the above copyright
	# notice, this list of conditions and the following disclaimer;
	# redistributions in binary form must reproduce the above copyright
	# notice, this list of conditions and the following disclaimer in the
	# documentation and/or other materials provided with the distribution;
	# neither the name of the copyright holders nor the names of its
	# contributors may be used to endorse or promote products derived from
	# this software without specific prior written permission.
	#
	# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	#
	# Author: David Guillen Fandos

	/*! \page gem5PowerModel Gem5 Power & Thermal model

	\tableofcontents

	This document gives an overview of the power and thermal modelling
	infrastructure in Gem5. The purpose is to give a high level view of
	all the pieces involved and how they interact with each other and
	the simulator.

	\section gem5_PM_CD Class overview

	Classes involved in the power model are:

	- PowerModel: Represents a power model for a hardware component.

	- PowerModelState: Represents a power model for a hardware component
	in a certain power state. It is an abstract class that defines an
	interface that must be implemented for each model.

	- MathExprPowerModel: Simple implementation of PowerModelState that
	assumes that power can be modeled using a simple power

	Classes involved in the thermal model are:

	- ThermalModel: Contains the system thermal model logic and state.
	It performs the power query and temperature update. It also enables
	gem5 to query for temperature (for OS reporting).

	- ThermalDomain: Represents an entity that generates heat. It's
	essentially a group of SimObjects grouped under a SubSystem component
	that have its own thermal behaviour.

	- ThermalNode: Represents a node in the thermal circuital equivalent.
	The node has a temperature and interacts with other nodes through
	connections (thermal resistors and capacitors).

	- ThermalReference: Temperature reference for the thermal model
	(essentially a thermal node with a fixed temperature), can be used
	to model air or any other constant temperature domains.

	- ThermalEntity: A thermal component that connects two thermal nodes
	and models a thermal impedance between them. This class is just an
	abstract interface.

	- ThermalResistor: Implements ThermalEntity to model a thermal resistance
	between the two nodes it connects. Thermal resistances model the
	capacity of a material to transfer heat (units in K/W).

	- ThermalCapacitor. Implements ThermalEntity to model a thermal
	capacitance. Thermal capacitors are used to model material's thermal
	capacitance, this is, the ability to change a certain material
	temperature (units in J/K).

	\section gem5_thermal Thermal model

	The thermal model works by creating a circuital equivalent of the
	simulated platform. Each node in the circuit has a temperature (as
	voltage equivalent) and power flows between nodes (as current in a
	circuit).

	To build this equivalent temperature model the platform is required
	to group the power actors (any component that has a power model)
	under SubSystems and attach ThermalDomains to those subsystems.
	Other components might also be created (like ThermalReferences) and
	connected all together by creating thermal entities (capacitors and
	resistors).

	Last step to conclude the thermal model is to create the ThermalModel
	instance itself and attach all the instances used to it, so it can
	properly update them at runtime. Only one thermal model instance is
	supported right now and it will automatically report temperature when
	appropriate (ie. platform sensor devices).

	\section gem5_power Power model

	Every ClockedObject has a power model associated. If this power model is
	non-null power will be calculated at every stats dump (although it might
	be possible to force power evaluation at any other point, if the power
	model uses the stats, it is a good idea to keep both events in sync).
	The definition of a power model is quite vague in the sense that it is
	as flexible as users want it to be. The only enforced contraints so far
	is the fact that a power model has several power state models, one for
	each possible power state for that hardware block. When it comes to compute
	power consumption the power is just the weighted average of each power model.

	A power state model is essentially an interface that allows us to define two
	power functions for dynamic and static. As an example implementation a class
	called MathExprPowerModel has been provided. This implementation allows the
	user to define a power model as an equation involving several statistics.
	There's also some automatic (or "magic") variables such as "temp", which
	reports temperature.
	*/