src/mem/comm_monitor.hh

/*
 * Copyright (c) 2012-2013, 2015, 2018-2019 ARM Limited
 * Copyright (c) 2016 Google Inc.
 * Copyright (c) 2017, Centre National de la Recherche Scientifique
 * All rights reserved.
 *
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 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
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 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
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#ifndef __MEM_COMM_MONITOR_HH__
#define __MEM_COMM_MONITOR_HH__

#include "base/statistics.hh"
#include "mem/port.hh"
#include "params/CommMonitor.hh"
#include "sim/probe/mem.hh"
#include "sim/sim_object.hh"

namespace gem5
{

/**
 * The communication monitor is a SimObject which can monitor statistics of
 * the communication happening between two ports in the memory system.
 *
 * Currently the following stats are implemented: Histograms of read/write
 * transactions, read/write burst lengths, read/write bandwidth,
 * outstanding read/write requests, read latency and inter transaction time
 * (read-read, write-write, read/write-read/write). Furthermore it allows
 * to capture the number of accesses to an address over time ("heat map").
 * All stats can be disabled from Python.
 */
class CommMonitor : public SimObject
{

  public: // Construction & SimObject interfaces

    /** Parameters of communication monitor */
    using Params = CommMonitorParams;

    /**
     * Constructor based on the Python params
     *
     * @param params Python parameters
     */
    CommMonitor(const Params &params);

    void init() override;
    void startup() override;
    void regProbePoints() override;

  public: // SimObject interfaces
    Port &getPort(const std::string &if_name,
                  PortID idx=InvalidPortID) override;

  private:

    /**
     * Sender state class for the monitor so that we can annotate
     * packets with a transmit time and receive time.
     */
    class CommMonitorSenderState : public Packet::SenderState
    {

      public:

        /**
         * Construct a new sender state and store the time so we can
         * calculate round-trip latency.
         *
         * @param _transmitTime Time of packet transmission
         */
        CommMonitorSenderState(Tick _transmitTime)
            : transmitTime(_transmitTime)
        { }

        /** Destructor */
        ~CommMonitorSenderState() { }

        /** Tick when request is transmitted */
        Tick transmitTime;

    };

    /**
     * This is the request port of the communication monitor. All recv
     * functions call a function in CommMonitor, where the
     * send function of the CPU-side port is called. Besides this, these
     * functions can also perform actions for capturing statistics.
     */
    class MonitorRequestPort : public RequestPort
    {

      public:

        MonitorRequestPort(const std::string& _name, CommMonitor& _mon)
            : RequestPort(_name), mon(_mon)
        { }

      protected:

        void recvFunctionalSnoop(PacketPtr pkt)
        {
            mon.recvFunctionalSnoop(pkt);
        }

        Tick recvAtomicSnoop(PacketPtr pkt)
        {
            return mon.recvAtomicSnoop(pkt);
        }

        bool recvTimingResp(PacketPtr pkt)
        {
            return mon.recvTimingResp(pkt);
        }

        void recvTimingSnoopReq(PacketPtr pkt)
        {
            mon.recvTimingSnoopReq(pkt);
        }

        void recvRangeChange()
        {
            mon.recvRangeChange();
        }

        bool isSnooping() const
        {
            return mon.isSnooping();
        }

        void recvReqRetry()
        {
            mon.recvReqRetry();
        }

        void recvRetrySnoopResp()
        {
            mon.recvRetrySnoopResp();
        }

      private:

        CommMonitor& mon;

    };

    /** Instance of request port, facing the memory side */
    MonitorRequestPort memSidePort;

    /**
     * This is the CPU-side port of the communication monitor. All recv
     * functions call a function in CommMonitor, where the
     * send function of the request port is called. Besides this, these
     * functions can also perform actions for capturing statistics.
     */
    class MonitorResponsePort : public ResponsePort
    {

      public:

        MonitorResponsePort(const std::string& _name, CommMonitor& _mon)
            : ResponsePort(_name), mon(_mon)
        { }

      protected:

        void recvFunctional(PacketPtr pkt)
        {
            mon.recvFunctional(pkt);
        }

        Tick recvAtomic(PacketPtr pkt)
        {
            return mon.recvAtomic(pkt);
        }

        bool recvTimingReq(PacketPtr pkt)
        {
            return mon.recvTimingReq(pkt);
        }

        bool recvTimingSnoopResp(PacketPtr pkt)
        {
            return mon.recvTimingSnoopResp(pkt);
        }

        AddrRangeList getAddrRanges() const
        {
            return mon.getAddrRanges();
        }

        void recvRespRetry()
        {
            mon.recvRespRetry();
        }

        bool tryTiming(PacketPtr pkt)
        {
            return mon.tryTiming(pkt);
        }

      private:

        CommMonitor& mon;

    };

    /** Instance of response port, i.e. on the CPU side */
    MonitorResponsePort cpuSidePort;

    void recvFunctional(PacketPtr pkt);

    void recvFunctionalSnoop(PacketPtr pkt);

    Tick recvAtomic(PacketPtr pkt);

    Tick recvAtomicSnoop(PacketPtr pkt);

    bool recvTimingReq(PacketPtr pkt);

    bool recvTimingResp(PacketPtr pkt);

    void recvTimingSnoopReq(PacketPtr pkt);

    bool recvTimingSnoopResp(PacketPtr pkt);

    void recvRetrySnoopResp();

    AddrRangeList getAddrRanges() const;

    bool isSnooping() const;

    void recvReqRetry();

    void recvRespRetry();

    void recvRangeChange();

    bool tryTiming(PacketPtr pkt);

    /** Stats declarations, all in a struct for convenience. */
    struct MonitorStats : public statistics::Group
    {
        /** Disable flag for burst length histograms **/
        bool disableBurstLengthHists;

        /** Histogram of read burst lengths */
        statistics::Histogram readBurstLengthHist;

        /** Histogram of write burst lengths */
        statistics::Histogram writeBurstLengthHist;

        /** Disable flag for the bandwidth histograms */
        bool disableBandwidthHists;

        /**
         * Histogram for read bandwidth per sample window. The
         * internal counter is an unsigned int rather than a stat.
         */
        unsigned int readBytes;
        statistics::Histogram readBandwidthHist;
        statistics::Scalar totalReadBytes;
        statistics::Formula averageReadBandwidth;

        /**
         * Histogram for write bandwidth per sample window. The
         * internal counter is an unsigned int rather than a stat.
         */
        unsigned int writtenBytes;
        statistics::Histogram writeBandwidthHist;
        statistics::Scalar totalWrittenBytes;
        statistics::Formula averageWriteBandwidth;

        /** Disable flag for latency histograms. */
        bool disableLatencyHists;

        /** Histogram of read request-to-response latencies */
        statistics::Histogram readLatencyHist;

        /** Histogram of write request-to-response latencies */
        statistics::Histogram writeLatencyHist;

        /** Disable flag for ITT distributions. */
        bool disableITTDists;

        /**
         * Inter transaction time (ITT) distributions. There are
         * histograms of the time between two read, write or arbitrary
         * accesses. The time of a request is the tick at which the
         * request is forwarded by the monitor.
         */
        statistics::Distribution ittReadRead;
        statistics::Distribution ittWriteWrite;
        statistics::Distribution ittReqReq;
        Tick timeOfLastRead;
        Tick timeOfLastWrite;
        Tick timeOfLastReq;

        /** Disable flag for outstanding histograms. */
        bool disableOutstandingHists;

        /**
         * Histogram of outstanding read requests. Counter for
         * outstanding read requests is an unsigned integer because
         * it should not be reset when stats are reset.
         */
        statistics::Histogram outstandingReadsHist;
        unsigned int outstandingReadReqs;

        /**
         * Histogram of outstanding write requests. Counter for
         * outstanding write requests is an unsigned integer because
         * it should not be reset when stats are reset.
         */
        statistics::Histogram outstandingWritesHist;
        unsigned int outstandingWriteReqs;

        /** Disable flag for transaction histograms. */
        bool disableTransactionHists;

        /** Histogram of number of read transactions per time bin */
        statistics::Histogram readTransHist;
        unsigned int readTrans;

        /** Histogram of number of timing write transactions per time bin */
        statistics::Histogram writeTransHist;
        unsigned int writeTrans;

        /** Disable flag for address distributions. */
        bool disableAddrDists;

        /** Address mask for sources of read accesses to be captured */
        const Addr readAddrMask;

        /** Address mask for sources of write accesses to be captured */
        const Addr writeAddrMask;

        /**
         * Histogram of number of read accesses to addresses over
         * time.
         */
        statistics::SparseHistogram readAddrDist;

        /**
         * Histogram of number of write accesses to addresses over
         * time.
         */
        statistics::SparseHistogram writeAddrDist;

        /**
         * Create the monitor stats and initialise all the members
         * that are not statistics themselves, but used to control the
         * stats or track values during a sample period.
         */
        MonitorStats(statistics::Group *parent,
            const CommMonitorParams &params);

        void updateReqStats(const probing::PacketInfo& pkt, bool is_atomic,
                            bool expects_response);
        void updateRespStats(const probing::PacketInfo& pkt, Tick latency,
                             bool is_atomic);
    };

    /** This function is called periodically at the end of each time bin */
    void samplePeriodic();

    /** Periodic event called at the end of each simulation time bin */
    EventFunctionWrapper samplePeriodicEvent;

    /**
     *@{
     * @name Configuration
     */

    /** Length of simulation time bin*/
    const Tick samplePeriodTicks;
    /** Sample period in seconds */
    const double samplePeriod;

    /** @} */

    /** Instantiate stats */
    MonitorStats stats;

  protected: // Probe points
    /**
     * @{
     * @name Memory system probe points
     */

    /** Successfully forwarded request packet */
    probing::PacketUPtr ppPktReq;

    /** Successfully forwarded response packet */
    probing::PacketUPtr ppPktResp;

    /** @} */
};

} // namespace gem5

#endif //__MEM_COMM_MONITOR_HH__