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2015-07-07sim: Decouple draining from the SimObject hierarchyAndreas Sandberg
Draining is currently done by traversing the SimObject graph and calling drain()/drainResume() on the SimObjects. This is not ideal when non-SimObjects (e.g., ports) need draining since this means that SimObjects owning those objects need to be aware of this. This changeset moves the responsibility for finding objects that need draining from SimObjects and the Python-side of the simulator to the DrainManager. The DrainManager now maintains a set of all objects that need draining. To reduce the overhead in classes owning non-SimObjects that need draining, objects inheriting from Drainable now automatically register with the DrainManager. If such an object is destroyed, it is automatically unregistered. This means that drain() and drainResume() should never be called directly on a Drainable object. While implementing the new functionality, the DrainManager has now been made thread safe. In practice, this means that it takes a lock whenever it manipulates the set of Drainable objects since SimObjects in different threads may create Drainable objects dynamically. Similarly, the drain counter is now an atomic_uint, which ensures that it is manipulated correctly when objects signal that they are done draining. A nice side effect of these changes is that it makes the drain state changes stricter, which the simulation scripts can exploit to avoid redundant drains.
2015-07-07sim: Refactor the serialization base classAndreas Sandberg
Objects that are can be serialized are supposed to inherit from the Serializable class. This class is meant to provide a unified API for such objects. However, so far it has mainly been used by SimObjects due to some fundamental design limitations. This changeset redesigns to the serialization interface to make it more generic and hide the underlying checkpoint storage. Specifically: * Add a set of APIs to serialize into a subsection of the current object. Previously, objects that needed this functionality would use ad-hoc solutions using nameOut() and section name generation. In the new world, an object that implements the interface has the methods serializeSection() and unserializeSection() that serialize into a named /subsection/ of the current object. Calling serialize() serializes an object into the current section. * Move the name() method from Serializable to SimObject as it is no longer needed for serialization. The fully qualified section name is generated by the main serialization code on the fly as objects serialize sub-objects. * Add a scoped ScopedCheckpointSection helper class. Some objects need to serialize data structures, that are not deriving from Serializable, into subsections. Previously, this was done using nameOut() and manual section name generation. To simplify this, this changeset introduces a ScopedCheckpointSection() helper class. When this class is instantiated, it adds a new /subsection/ and subsequent serialization calls during the lifetime of this helper class happen inside this section (or a subsection in case of nested sections). * The serialize() call is now const which prevents accidental state manipulation during serialization. Objects that rely on modifying state can use the serializeOld() call instead. The default implementation simply calls serialize(). Note: The old-style calls need to be explicitly called using the serializeOld()/serializeSectionOld() style APIs. These are used by default when serializing SimObjects. * Both the input and output checkpoints now use their own named types. This hides underlying checkpoint implementation from objects that need checkpointing and makes it easier to change the underlying checkpoint storage code.
2014-10-16config: Add the ability to read a config file using C++ and PythonAndreas Hansson
This patch adds the ability to load in config.ini files generated from gem5 into another instance of gem5 built without Python configuration support. The intended use case is for configuring gem5 when it is a library embedded in another simulation system. A parallel config file reader is also provided purely in Python to demonstrate the approach taken and to provided similar functionality for as-yet-unknown use models. The Python configuration file reader can read both .ini and .json files. C++ configuration file reading: A command line option has been added for scons to enable C++ configuration file reading: --with-cxx-config There is an example in util/cxx_config that shows C++ configuration in action. util/cxx_config/README explains how to build the example. Configuration is achieved by the object CxxConfigManager. It handles reading object descriptions from a CxxConfigFileBase object which wraps a config file reader. The wrapper class CxxIniFile is provided which wraps an IniFile for reading .ini files. Reading .json files from C++ would be possible with a similar wrapper and a JSON parser. After reading object descriptions, CxxConfigManager creates SimObjectParam-derived objects from the classes in the (generated with this patch) directory build/ARCH/cxx_config CxxConfigManager can then build SimObjects from those SimObjectParams (in an order dictated by the SimObject-value parameters on other objects) and bind ports of the produced SimObjects. A minimal set of instantiate-replacing member functions are provided by CxxConfigManager and few of the member functions of SimObject (such as drain) are extended onto CxxConfigManager. Python configuration file reading (configs/example/read_config.py): A Python version of the reader is also supplied with a similar interface to CxxConfigFileBase (In Python: ConfigFile) to config file readers. The Python config file reading will handle both .ini and .json files. The object construction strategy is slightly different in Python from the C++ reader as you need to avoid objects prematurely becoming the children of other objects when setting parameters. Port binding also needs to be strictly in the same port-index order as the original instantiation.