sim: Update the SimObject documentation
Includes a small change in sim_object.cc that adds the name space to the output stream parameter in serializeAll. Leaving out the name space unfortunately confuses Doxygen.
This commit is contained in:
Andreas Sandberg
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2f397f314b
commit
d4a6d9846a
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@ -113,7 +113,7 @@ SimObject::resetStats()
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// static function: serialize all SimObjects.
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//
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void
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SimObject::serializeAll(ostream &os)
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SimObject::serializeAll(std::ostream &os)
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{
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SimObjectList::reverse_iterator ri = simObjectList.rbegin();
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SimObjectList::reverse_iterator rend = simObjectList.rend();
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@ -51,18 +51,94 @@
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class BaseCPU;
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class Event;
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/*
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/**
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* Abstract superclass for simulation objects. Represents things that
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* correspond to physical components and can be specified via the
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* config file (CPUs, caches, etc.).
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*
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* SimObject initialization is controlled by the instantiate method in
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* src/python/m5/simulate.py. There are slightly different
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* initialization paths when starting the simulation afresh and when
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* loading from a checkpoint. After instantiation and connecting
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* ports, simulate.py initializes the object using the following call
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* sequence:
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*
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* <ol>
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* <li>SimObject::init()
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* <li>SimObject::regStats()
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* <li><ul>
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* <li>SimObject::initState() if starting afresh.
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* <li>SimObject::loadState() if restoring from a checkpoint.
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* </ul>
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* <li>SimObject::resetStats()
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* <li>SimObject::startup()
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* <li>SimObject::resume() if resuming from a checkpoint.
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* </ol>
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*
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* An object's internal state needs to be drained when creating a
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* checkpoint, switching between CPU models, or switching between
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* timing models. Once the internal state has been drained from
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* <i>all</i> objects in the system, the objects are serialized to
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* disc or the configuration change takes place. The process works as
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* follows (see simulate.py for details):
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*
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* <ol>
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* <li>An instance of a CountedDrainEvent is created to keep track of
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* how many objects need to be drained. The object maintains an
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* internal counter that is decreased every time its
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* CountedDrainEvent::process() method is called. When the counter
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* reaches zero, the simulation is stopped.
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*
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* <li>Call SimObject::drain() for every object in the
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* system. Draining has completed if all of them return
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* zero. Otherwise, the sum of the return values is loaded into
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* the counter of the CountedDrainEvent. A pointer of the drain
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* event is passed as an argument to the drain() method.
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*
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* <li>Continue simulation. When an object has finished draining its
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* internal state, it calls CountedDrainEvent::process() on the
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* CountedDrainEvent. When counter in the CountedDrainEvent reaches
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* zero, the simulation stops.
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*
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* <li>Check if any object still needs draining, if so repeat the
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* process above.
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*
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* <li>Serialize objects, switch CPU model, or change timing model.
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*
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* <li>Call SimObject::resume() and continue the simulation.
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* </ol>
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*
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* @note Whenever a method is called on all objects in the simulator's
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* object tree (e.g., init(), startup(), or loadState()), a pre-order
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* depth-first traversal is performed (see descendants() in
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* SimObject.py). This has the effect of calling the method on the
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* parent node <i>before</i> its children.
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*/
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class SimObject : public EventManager, public Serializable
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{
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public:
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/**
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* Object drain/handover states
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*
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* An object starts out in the Running state. When the simulator
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* prepares to take a snapshot or prepares a CPU for handover, it
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* calls the drain() method to transfer the object into the
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* Draining or Drained state. If any object enters the Draining
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* state (drain() returning >0), simulation continues until it all
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* objects have entered the Drained.
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*
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* The before resuming simulation, the simulator calls resume() to
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* transfer the object to the Running state.
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*
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* \note Even though the state of an object (visible to the rest
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* of the world through getState()) could be used to determine if
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* all objects have entered the Drained state, the protocol is
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* actually a bit more elaborate. See drain() for details.
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*/
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enum State {
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Running,
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Draining,
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Drained
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Running, /** Running normally */
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Draining, /** Draining buffers pending serialization/handover */
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Drained /** Buffers drained, ready for serialization/handover */
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};
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private:
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@ -77,10 +153,11 @@ class SimObject : public EventManager, public Serializable
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private:
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typedef std::vector<SimObject *> SimObjectList;
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// list of all instantiated simulation objects
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/** List of all instantiated simulation objects. */
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static SimObjectList simObjectList;
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protected:
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/** Cached copy of the object parameters. */
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const SimObjectParams *_params;
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public:
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@ -93,11 +170,6 @@ class SimObject : public EventManager, public Serializable
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virtual const std::string name() const { return params()->name; }
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// The following SimObject initialization methods are called from
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// the instantiate() method in src/python/m5/simulate.py. See
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// that function for details on how/when these methods are
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// invoked.
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/**
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* init() is called after all C++ SimObjects have been created and
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* all ports are connected. Initializations that are independent
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@ -114,6 +186,8 @@ class SimObject : public EventManager, public Serializable
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* other behaviors, e.g., doing other programmed initializations
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* after unserialize(), or complaining if no checkpoint section is
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* found.
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*
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* @param cp Checkpoint to restore the state from.
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*/
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virtual void loadState(Checkpoint *cp);
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@ -124,8 +198,14 @@ class SimObject : public EventManager, public Serializable
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*/
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virtual void initState();
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// register statistics for this object
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/**
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* Register statistics for this object.
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*/
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virtual void regStats();
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/**
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* Reset statistics associated with this object.
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*/
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virtual void resetStats();
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/**
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@ -136,18 +216,73 @@ class SimObject : public EventManager, public Serializable
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*/
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virtual void startup();
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// static: call nameOut() & serialize() on all SimObjects
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static void serializeAll(std::ostream &);
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/**
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* Serialize all SimObjects in the system.
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*/
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static void serializeAll(std::ostream &os);
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// Methods to drain objects in order to take checkpoints
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// Or switch from timing -> atomic memory model
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// Drain returns 0 if the simobject can drain immediately or
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// the number of times the drain_event's process function will be called
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// before the object will be done draining. Normally this should be 1
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/**
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* Determine if an object needs draining and register a drain
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* event.
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*
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* When draining the state of an object, the simulator calls drain
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* with a pointer to a drain event. If the object does not need
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* further simulation to drain internal buffers, it switched to
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* the Drained state and returns 0, otherwise it switches to the
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* Draining state and returns the number of times that it will
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* call Event::process() on the drain event. Most objects are
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* expected to return either 0 or 1.
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*
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* The default implementation simply switches to the Drained state
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* and returns 0.
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*
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* @note An object that has entered the Drained state can be
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* disturbed by other objects in the system and consequently be
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* forced to enter the Draining state again. The simulator
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* therefore repeats the draining process until all objects return
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* 0 on the first call to drain().
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*
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* @param drain_event Event to use to inform the simulator when
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* the draining has completed.
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*
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* @return 0 if the object is ready for serialization now, >0 if
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* it needs further simulation.
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*/
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virtual unsigned int drain(Event *drain_event);
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/**
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* Switch an object in the Drained stated into the Running state.
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*/
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virtual void resume();
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/**
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* Change the memory mode the simulator operates in.
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*
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* @note Should only be implemented in the System object.
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*/
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virtual void setMemoryMode(Enums::MemoryMode new_mode);
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/**
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* Prepare a CPU model to be switched out, invoked on active CPUs
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* that are about to be replaced.
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*
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* @note This should only be implemented in CPU models.
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*/
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virtual void switchOut();
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/**
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* Load the state of a CPU from the previous CPU object, invoked
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* on all new CPUs that are about to be switched in.
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*
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* A CPU model implementing this method is expected to initialize
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* its state from the old CPU and connect its memory (unless they
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* are already connected) to the memories connected to the old
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* CPU.
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*
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* @note This should only be implemented in CPU models.
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*
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* @param cpu CPU to initialize read state from.
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*/
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virtual void takeOverFrom(BaseCPU *cpu);
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#ifdef DEBUG
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