sim: simulate with multiple threads and event queues

This patch adds support for simulating with multiple threads, each of
which operates on an event queue.  Each sim object specifies which eventq
is would like to be on.  A custom barrier implementation is being added
using which eventqs synchronize.

The patch was tested in two different configurations:
1. ruby_network_test.py: in this simulation L1 cache controllers receive
   requests from the cpu. The requests are replied to immediately without
   any communication taking place with any other level.
2. twosys-tsunami-simple-atomic: this configuration simulates a client-server
   system which are connected by an ethernet link.

We still lack the ability to communicate using message buffers or ports. But
other things like simulation start and end, synchronizing after every quantum
are working.

Committed by: Nilay Vaish

1 files changed, 230 insertions, 0 deletions

diff --git a/src/sim/global_event.hh b/src/sim/global_event.hh
new file mode 100644
index 000000000..7b5fd7485
--- /dev/null
+++ b/src/sim/global_event.hh
@@ -0,0 +1,230 @@
+/*
+ * Copyright (c) 2011-2013 Advanced Micro Devices, Inc.
+ * Copyright (c) 2013 Mark D. Hill and David A. Wood
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Steve Reinhardt
+ */
+
+#ifndef __SIM_GLOBAL_EVENT_HH__
+#define __SIM_GLOBAL_EVENT_HH__
+
+#include <mutex>
+#include <vector>
+
+#include "base/barrier.hh"
+#include "sim/eventq_impl.hh"
+
+/**
+ * @file sim/global_event.hh
+ * Global events and related declarations.
+ *
+ * A global event is an event that occurs across all threads, i.e.,
+ * globally.  It consists of a set of "local" (regular) Events, one
+ * per thread/event queue, a barrier object, and common state.  The
+ * local events are scheduled for the same tick.  The local event
+ * process() method enters the barrier to wait for other threads; once
+ * all threads reach that tick (and enter the associated barrier), the
+ * global event is triggered and its associated activity is performed.
+ *
+ * There are two basic global event patterns, GlobalEvent and
+ * GlobalSyncEvent.  GlobalEvent is the base class for typical global
+ * events, while GlobalSyncEvent is optimized for global
+ * synchronization operations.
+ */
+
+/**
+ * Common base class for GlobalEvent and GlobalSyncEvent.
+ */
+class BaseGlobalEvent : public EventBase
+{
+  private:
+      //! Mutex variable for providing exculsive right to schedule global
+      //! events. This is necessary so that a total order can be maintained
+      //! amongst the global events. Without ensuring the total order, it is
+      //! possible that threads execute global events in different orders,
+      //! which can result in a deadlock.
+      static std::mutex globalQMutex;
+
+  protected:
+
+    /// The base class for the local events that will synchronize
+    /// threads to perform the global event.  This class is abstract,
+    /// since it derives from the abstract Event class but still does
+    /// not define the required process() method.
+    class BarrierEvent : public Event
+    {
+      protected:
+        BaseGlobalEvent *_globalEvent;
+
+        BarrierEvent(BaseGlobalEvent *global_event, Priority p, Flags f)
+            : Event(p, f), _globalEvent(global_event)
+        {
+        }
+
+        ~BarrierEvent();
+
+        friend class BaseGlobalEvent;
+
+        bool globalBarrier()
+        {
+            return _globalEvent->barrier->wait();
+        }
+
+      public:
+        virtual BaseGlobalEvent *globalEvent() { return _globalEvent; }
+    };
+
+    //! The barrier that all threads wait on before performing the
+    //! global event.
+    Barrier *barrier;
+
+    //! The individual local event instances (one per thread/event queue).
+    std::vector<BarrierEvent *> barrierEvent;
+
+  public:
+    BaseGlobalEvent(Priority p, Flags f);
+
+    virtual ~BaseGlobalEvent();
+
+    virtual void process() = 0;
+
+    virtual const char *description() const = 0;
+
+    void schedule(Tick when);
+
+    bool scheduled() const
+    {
+        bool sched = false;
+        for (uint32_t i = 0; i < numMainEventQueues; ++i) {
+            sched = sched || barrierEvent[i]->scheduled();
+        }
+
+        return sched;
+    }
+
+    Tick when() const
+    {
+        assert(numMainEventQueues > 0);
+        return barrierEvent[0]->when();
+    }
+
+    void deschedule();
+    void reschedule(Tick when);
+};
+
+
+/**
+ * Funky intermediate class to support CRTP so that we can have a
+ * common constructor to create the local events, even though the
+ * types of the local events are defined in the derived classes.
+ */
+template <class Derived>
+class BaseGlobalEventTemplate : public BaseGlobalEvent
+{
+  protected:
+    BaseGlobalEventTemplate(Priority p, Flags f)
+        : BaseGlobalEvent(p, f)
+    {
+        for (int i = 0; i < numMainEventQueues; ++i)
+            barrierEvent[i] = new typename Derived::BarrierEvent(this, p, f);
+    }
+};
+
+
+/**
+ * The main global event class.  Ordinary global events should derive
+ * from this class, and define process() to specify the action to be
+ * taken when the event is reached.  All threads will synchronize at a
+ * barrier, exactly one of the threads will execute the process()
+ * method, then the threads will synchronize again so that none of
+ * them continue until process() is complete.
+ */
+class GlobalEvent : public BaseGlobalEventTemplate<GlobalEvent>
+{
+  public:
+    typedef BaseGlobalEventTemplate<GlobalEvent> Base;
+
+    class BarrierEvent : public Base::BarrierEvent
+    {
+      public:
+        void process();
+        BarrierEvent(Base *global_event, Priority p, Flags f)
+            : Base::BarrierEvent(global_event, p, f)
+        { }
+    };
+
+    GlobalEvent(Priority p, Flags f)
+        : Base(p, f)
+    { }
+
+    GlobalEvent(Tick when, Priority p, Flags f)
+        : Base(p, f)
+    {
+        schedule(when);
+    }
+
+    virtual void process() = 0;
+};
+
+/**
+ * A special global event that synchronizes all threads and forces
+ * them to process asynchronously enqueued events.  Useful for
+ * separating quanta in a quantum-based parallel simulation.
+ */
+class GlobalSyncEvent : public BaseGlobalEventTemplate<GlobalSyncEvent>
+{
+  public:
+    typedef BaseGlobalEventTemplate<GlobalSyncEvent> Base;
+
+    class BarrierEvent : public Base::BarrierEvent
+    {
+      public:
+        void process();
+        BarrierEvent(Base *global_event, Priority p, Flags f)
+            : Base::BarrierEvent(global_event, p, f)
+        { }
+    };
+
+    GlobalSyncEvent(Priority p, Flags f)
+        : Base(p, f)
+    { }
+
+    GlobalSyncEvent(Tick when, Tick _repeat, Priority p, Flags f)
+        : Base(p, f), repeat(_repeat)
+    {
+        schedule(when);
+    }
+
+    void process();
+
+    const char *description() const;
+
+    Tick repeat;
+};
+
+
+#endif // __SIM_GLOBAL_EVENT_HH__