dist_iface.hh

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 * Authors: Gabor Dozsa
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/* @file
 * The interface class for dist gem5 simulations.
 *
 * dist-gem5 is an extension to gem5 to enable parallel simulation of a
 * distributed system (e.g. simulation of a pool of machines
 * connected by Ethernet links). A dist gem5 run consists of seperate gem5
 * processes running in parallel. Each gem5 process executes
 * the simulation of a component of the simulated distributed system.
 * (An example component can be a dist-core board with an Ethernet NIC.)
 * The DistIface class below provides services to transfer data and
 * control messages among the gem5 processes. The main such services are
 * as follows.
 *
 * 1. Send a data packet coming from a simulated Ethernet link. The packet
 * will be transferred to (all) the target(s) gem5 processes. The send
 * operation is always performed by the simulation thread, i.e. the gem5
 * thread that is processing the event queue associated with the simulated
 * Ethernet link.
 *
 * 2. Spawn a receiver thread to process messages coming in from the
 * from other gem5 processes. Each simulated Ethernet link has its own
 * associated receiver thread. The receiver thread saves the incoming packet
 * and schedule an appropriate receive event in the event queue.
 *
 * 3. Schedule a global barrier event periodically to keep the gem5
 * processes in sync.
 * Periodic barrier event to keep peer gem5 processes in sync. The basic idea
 * is that no gem5 process can go ahead further than the simulated link
 * transmission delay to ensure that a corresponding receive event can always
 * be scheduled for any message coming in from a peer gem5 process.
 *
 *
 *
 * This interface is an abstract class. It can work with various low level
 * send/receive service implementations (e.g. TCP/IP, MPI,...). A TCP
 * stream socket version is implemented in src/dev/net/tcp_iface.[hh,cc].
 */
#ifndef __DEV_DIST_IFACE_HH__
#define __DEV_DIST_IFACE_HH__

#include <array>
#include <mutex>
#include <queue>
#include <thread>
#include <utility>

#include "base/misc.hh"
#include "dev/net/dist_packet.hh"
#include "dev/net/etherpkt.hh"
#include "sim/core.hh"
#include "sim/drain.hh"
#include "sim/global_event.hh"
#include "sim/serialize.hh"

class EventManager;
class System;
class ThreadContext;

class DistIface : public Drainable, public Serializable
{
  public:
    typedef DistHeaderPkt::Header Header;

  protected:
    typedef DistHeaderPkt::MsgType MsgType;
    typedef DistHeaderPkt::ReqType ReqType;

  private:
    class SyncEvent;
    class Sync : public Serializable
    {
      protected:
        std::mutex lock;
        std::condition_variable cv;
        unsigned waitNum;
        bool doExit;
        bool doCkpt;
        bool doStopSync;
        Tick nextRepeat;
        Tick nextAt;
        bool isAbort;

        friend class SyncEvent;

      public:
        void init(Tick start, Tick repeat);
        virtual bool run(bool same_tick) = 0;
        virtual bool progress(Tick send_tick,
                              Tick next_repeat,
                              ReqType do_ckpt,
                              ReqType do_exit,
                              ReqType do_stop_sync) = 0;
        void abort();

        virtual void requestCkpt(ReqType req) = 0;
        virtual void requestExit(ReqType req) = 0;
        virtual void requestStopSync(ReqType req) = 0;

        void drainComplete();

        virtual void serialize(CheckpointOut &cp) const override = 0;
        virtual void unserialize(CheckpointIn &cp) override = 0;
    };

    class SyncNode: public Sync
    {
      private:
        ReqType needExit;
        ReqType needCkpt;
        ReqType needStopSync;

      public:

        SyncNode();
        ~SyncNode() {}
        bool run(bool same_tick) override;
        bool progress(Tick max_req_tick,
                      Tick next_repeat,
                      ReqType do_ckpt,
                      ReqType do_exit,
                      ReqType do_stop_sync) override;

        void requestCkpt(ReqType req) override;
        void requestExit(ReqType req) override;
        void requestStopSync(ReqType req) override;

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

    class SyncSwitch: public Sync
    {
      private:
        unsigned numExitReq;
        unsigned numCkptReq;
        unsigned numStopSyncReq;
        unsigned numNodes;

      public:
        SyncSwitch(int num_nodes);
        ~SyncSwitch() {}

        bool run(bool same_tick) override;
        bool progress(Tick max_req_tick,
                      Tick next_repeat,
                      ReqType do_ckpt,
                      ReqType do_exit,
                      ReqType do_stop_sync) override;

        void requestCkpt(ReqType) override {
            panic("Switch requested checkpoint");
        }
        void requestExit(ReqType) override {
            panic("Switch requested exit");
        }
        void requestStopSync(ReqType) override {
            panic("Switch requested stop sync");
        }

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

    class SyncEvent : public GlobalSyncEvent
    {
      private:
        bool _draining;
      public:
        SyncEvent() : GlobalSyncEvent(Sim_Exit_Pri, 0), _draining(false) {}

        ~SyncEvent() {}
        void start();
        void process() override;

        bool draining() const { return _draining; }
        void draining(bool fl) { _draining = fl; }
    };
    class RecvScheduler : public Serializable
    {
      private:
        struct Desc : public Serializable
        {
            EthPacketPtr packet;
            Tick sendTick;
            Tick sendDelay;

            Desc() : sendTick(0), sendDelay(0) {}
            Desc(EthPacketPtr p, Tick s, Tick d) :
                packet(p), sendTick(s), sendDelay(d) {}
            Desc(const Desc &d) :
                packet(d.packet), sendTick(d.sendTick), sendDelay(d.sendDelay) {}

            void serialize(CheckpointOut &cp) const override;
            void unserialize(CheckpointIn &cp) override;
        };
        std::queue<Desc> descQueue;
        Tick prevRecvTick;
        Event *recvDone;
        Tick linkDelay;
        EventManager *eventManager;
        Tick calcReceiveTick(Tick send_tick,
                             Tick send_delay,
                             Tick prev_recv_tick);

        bool ckptRestore;

      public:
        RecvScheduler(EventManager *em) :
            prevRecvTick(0), recvDone(nullptr), linkDelay(0),
            eventManager(em), ckptRestore(false) {}

        void init(Event *recv_done, Tick link_delay);
        EthPacketPtr popPacket();
        void pushPacket(EthPacketPtr new_packet,
                        Tick send_tick,
                        Tick send_delay);

        void serialize(CheckpointOut &cp) const override;
        void unserialize(CheckpointIn &cp) override;
        void resumeRecvTicks();
    };
    Tick syncStart;
    Tick syncRepeat;
    std::thread *recvThread;
    RecvScheduler recvScheduler;
    bool syncStartOnPseudoOp;

  protected:
    unsigned rank;
    unsigned size;
    static unsigned distIfaceNum;
    unsigned distIfaceId;

    bool isMaster;

  private:
    static unsigned recvThreadsNum;
    static Sync *sync;
    static SyncEvent *syncEvent;
    static DistIface *master;
    static System *sys;
     static bool isSwitch;

  private:
    virtual void sendPacket(const Header &header, const EthPacketPtr &packet) = 0;
    virtual void sendCmd(const Header &header) = 0;
    virtual bool recvHeader(Header &header) = 0;
    virtual void recvPacket(const Header &header, EthPacketPtr &packet) = 0;
    virtual void initTransport() = 0;
    void spawnRecvThread(const Event *recv_done, Tick link_delay);
    void recvThreadFunc(Event *recv_done, Tick link_delay);

  public:

    DistIface(unsigned dist_rank,
              unsigned dist_size,
              Tick sync_start,
              Tick sync_repeat,
              EventManager *em,
              bool use_pseudo_op,
              bool is_switch,
              int num_nodes);

    virtual ~DistIface();
    void packetOut(EthPacketPtr pkt, Tick send_delay);
    EthPacketPtr packetIn() { return recvScheduler.popPacket(); }

    DrainState drain() override;
    void drainResume() override;
    void init(const Event *e, Tick link_delay);
    void startup();

    void serialize(CheckpointOut &cp) const override;
    void unserialize(CheckpointIn &cp) override;
    static bool readyToExit(Tick delay);
    static bool readyToCkpt(Tick delay, Tick period);
    static uint64_t rankParam();
    static uint64_t sizeParam();
    static void toggleSync(ThreadContext *tc);
 };

#endif