src/cpu/testers/traffic_gen/traffic_gen.hh

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#ifndef __CPU_TRAFFIC_GEN_TRAFFIC_GEN_HH__
#define __CPU_TRAFFIC_GEN_TRAFFIC_GEN_HH__

#include <unordered_map>

#include "cpu/testers/traffic_gen/base.hh"

namespace gem5
{

struct TrafficGenParams;

/**
 * The traffic generator is a module that generates stimuli for
 * the memory system, based on a collection of simple behaviours that
 * are either probabilistic or based on traces. It can be used stand
 * alone for creating test cases for interconnect and memory
 * controllers, or function as a black-box replacement for system
 * components that are not yet modelled in detail, e.g. a video engine
 * or baseband subsystem in an SoC.
 *
 * The traffic generator has a single request port that is used to send
 * requests, independent of the specific behaviour. The behaviour of
 * the traffic generator is specified in a configuration file, and this
 * file describes a state transition graph where each state is a
 * specific generator behaviour. Examples include idling, generating
 * linear address sequences, random sequences and replay of captured
 * traces. By describing these behaviours as states, it is straight
 * forward to create very complex behaviours, simply by arranging them
 * in graphs. The graph transitions can also be annotated with
 * probabilities, effectively making it a Markov Chain.
 */
class TrafficGen : public BaseTrafficGen
{
  private: // Params
    /**
     * The config file to parse.
     */
    const std::string configFile;

  private:
    /**
     * Resolve a file path in the configuration file.
     *
     * This method resolves a relative path to a file that has been
     * referenced in the configuration file. It first tries to resolve
     * the file relative to the configuration file's path. If that
     * fails, it falls back to constructing a path relative to the
     * current working directory.
     *
     * Absolute paths are returned unmodified.
     *
     * @param name Path to resolve
     */
    std::string resolveFile(const std::string &name);

     /**
      * Parse the config file and build the state map and
      * transition matrix.
      */
    void parseConfig();

    /**
     * Use the transition matrix to find the next state index.
     */
    size_t nextState();

    /** Struct to represent a probabilistic transition during parsing. */
    struct Transition
    {
        uint32_t from;
        uint32_t to;
        double p;
    };

    /** State transition matrix */
    std::vector<std::vector<double> > transitionMatrix;

    /** Index of the current state */
    uint32_t currState;

    /** Map of generator states */
    std::unordered_map<uint32_t, std::shared_ptr<BaseGen>> states;

  protected: // BaseTrafficGen
    std::shared_ptr<BaseGen> nextGenerator() override;

  public:

    TrafficGen(const TrafficGenParams &p);

    ~TrafficGen() {}

    void init() override;
    void initState() override;

    void serialize(CheckpointOut &cp) const override;
    void unserialize(CheckpointIn &cp) override;

};

} // namespace gem5

#endif //__CPU_TRAFFIC_GEN_TRAFFIC_GEN_HH__