ruby: Import ruby and slicc from GEMS

We eventually plan to replace the m5 cache hierarchy with the GEMS
hierarchy, but for now we will make both live alongside eachother.

4 files changed, 655 insertions, 0 deletions

diff --git a/src/mem/ruby/buffers/MessageBuffer.cc b/src/mem/ruby/buffers/MessageBuffer.cc
new file mode 100644
index 000000000..ff2547f0f
--- /dev/null
+++ b/src/mem/ruby/buffers/MessageBuffer.cc
@@ -0,0 +1,363 @@
+
+/*
+ * Copyright (c) 1999-2008 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.
+ */
+
+/*
+ * $Id$
+ */
+
+#include "MessageBuffer.hh"
+#include "RubyConfig.hh"
+
+MessageBuffer::MessageBuffer()
+{
+  m_msg_counter = 0;
+  m_consumer_ptr = NULL;
+  m_ordering_set = false;
+  m_strict_fifo = true;
+  m_size = 0;
+  m_max_size = -1;
+  m_last_arrival_time = 0;
+  m_randomization = true;
+  m_size_last_time_size_checked = 0;
+  m_time_last_time_size_checked = 0;
+  m_time_last_time_enqueue = 0;
+  m_time_last_time_pop = 0;
+  m_size_at_cycle_start = 0;
+  m_msgs_this_cycle = 0;
+  m_not_avail_count = 0;
+  m_priority_rank = 0;
+}
+
+MessageBuffer::MessageBuffer(const Chip* chip_ptr)  // The chip_ptr is ignored, but could be used for extra debugging
+{
+  m_msg_counter = 0;
+  m_consumer_ptr = NULL;
+  m_ordering_set = false;
+  m_strict_fifo = true;
+  m_size = 0;
+  m_max_size = -1;
+  m_last_arrival_time = 0;
+  m_randomization = true;
+  m_size_last_time_size_checked = 0;
+  m_time_last_time_size_checked = 0;
+  m_time_last_time_enqueue = 0;
+  m_time_last_time_pop = 0;
+  m_size_at_cycle_start = 0;
+  m_msgs_this_cycle = 0;
+  m_not_avail_count = 0;
+  m_priority_rank = 0;
+}
+
+int MessageBuffer::getSize()
+{
+  if(m_time_last_time_size_checked == g_eventQueue_ptr->getTime()){
+    return m_size_last_time_size_checked;
+  } else {
+    m_time_last_time_size_checked = g_eventQueue_ptr->getTime();
+    m_size_last_time_size_checked = m_size;
+    return m_size;
+  }
+}
+
+bool MessageBuffer::areNSlotsAvailable(int n)
+{
+
+  // fast path when message buffers have infinite size
+  if(m_max_size == -1) {
+    return true;
+  }
+
+  // determine my correct size for the current cycle
+  // pop operations shouldn't effect the network's visible size until next cycle,
+  // but enqueue operations effect the visible size immediately
+  int current_size = max(m_size_at_cycle_start, m_size);
+  if (m_time_last_time_pop < g_eventQueue_ptr->getTime()) {  // no pops this cycle - m_size is correct
+    current_size = m_size;
+  } else {
+    if (m_time_last_time_enqueue < g_eventQueue_ptr->getTime()) {  // no enqueues this cycle - m_size_at_cycle_start is correct
+      current_size = m_size_at_cycle_start;
+    } else {  // both pops and enqueues occured this cycle - add new enqueued msgs to m_size_at_cycle_start
+      current_size = m_size_at_cycle_start+m_msgs_this_cycle;
+    }
+  }
+
+  // now compare the new size with our max size
+  if(current_size+n <= m_max_size){
+    return true;
+  } else {
+    DEBUG_MSG(QUEUE_COMP,MedPrio,n);
+    DEBUG_MSG(QUEUE_COMP,MedPrio,current_size);
+    DEBUG_MSG(QUEUE_COMP,MedPrio,m_size);
+    DEBUG_MSG(QUEUE_COMP,MedPrio,m_max_size);
+    m_not_avail_count++;
+    return false;
+  }
+}
+
+const MsgPtr MessageBuffer::getMsgPtrCopy() const
+{
+  assert(isReady());
+
+  MsgPtr temp_msg;
+  temp_msg = *(m_prio_heap.peekMin().m_msgptr.ref());
+  assert(temp_msg.ref() != NULL);
+  return temp_msg;
+}
+
+const Message* MessageBuffer::peekAtHeadOfQueue() const
+{
+  const Message* msg_ptr;
+  DEBUG_NEWLINE(QUEUE_COMP,MedPrio);
+
+  DEBUG_MSG(QUEUE_COMP,MedPrio,"Peeking at head of queue " + m_name + " time: "
+            + int_to_string(g_eventQueue_ptr->getTime()) + ".");
+  assert(isReady());
+
+  msg_ptr = m_prio_heap.peekMin().m_msgptr.ref();
+  assert(msg_ptr != NULL);
+
+  DEBUG_EXPR(QUEUE_COMP,MedPrio,*msg_ptr);
+  DEBUG_NEWLINE(QUEUE_COMP,MedPrio);
+  return msg_ptr;
+}
+
+// FIXME - move me somewhere else
+int random_time()
+{
+  int time = 1;
+  time += random() & 0x3;  // [0...3]
+  if ((random() & 0x7) == 0) {  // 1 in 8 chance
+    time += 100 + (random() % 0xf); // 100 + [1...15]
+  }
+  return time;
+}
+
+void MessageBuffer::enqueue(const MsgPtr& message, Time delta)
+{
+  DEBUG_NEWLINE(QUEUE_COMP,HighPrio);
+  DEBUG_MSG(QUEUE_COMP,HighPrio,"enqueue " + m_name + " time: "
+            + int_to_string(g_eventQueue_ptr->getTime()) + ".");
+  DEBUG_EXPR(QUEUE_COMP,MedPrio,message);
+  DEBUG_NEWLINE(QUEUE_COMP,HighPrio);
+
+  m_msg_counter++;
+  m_size++;
+
+  // record current time incase we have a pop that also adjusts my size
+  if (m_time_last_time_enqueue < g_eventQueue_ptr->getTime()) {
+    m_msgs_this_cycle = 0;  // first msg this cycle
+    m_time_last_time_enqueue = g_eventQueue_ptr->getTime();
+  }
+  m_msgs_this_cycle++;
+
+  //  ASSERT(m_max_size == -1 || m_size <= m_max_size + 1);
+  // the plus one is a kluge because of a SLICC issue
+
+  if (!m_ordering_set) {
+    WARN_EXPR(*this);
+    WARN_EXPR(m_name);
+    ERROR_MSG("Ordering property of this queue has not been set");
+  }
+
+  // Calculate the arrival time of the message, that is, the first
+  // cycle the message can be dequeued.
+  assert(delta>0);
+  Time current_time = g_eventQueue_ptr->getTime();
+  Time arrival_time = 0;
+  if (!RANDOMIZATION || (m_randomization == false)) {
+    // No randomization
+    arrival_time = current_time + delta;
+
+  } else {
+    // Randomization - ignore delta
+    if (m_strict_fifo) {
+      if (m_last_arrival_time < current_time) {
+        m_last_arrival_time = current_time;
+      }
+      arrival_time = m_last_arrival_time + random_time();
+    } else {
+      arrival_time = current_time + random_time();
+    }
+  }
+
+  // Check the arrival time
+  assert(arrival_time > current_time);
+  if (m_strict_fifo) {
+    if (arrival_time >= m_last_arrival_time) {
+
+    } else {
+      WARN_EXPR(*this);
+      WARN_EXPR(m_name);
+      WARN_EXPR(current_time);
+      WARN_EXPR(delta);
+      WARN_EXPR(arrival_time);
+      WARN_EXPR(m_last_arrival_time);
+      ERROR_MSG("FIFO ordering violated");
+    }
+  }
+  m_last_arrival_time = arrival_time;
+
+  // compute the delay cycles and set enqueue time
+  Message* msg_ptr = NULL;
+  msg_ptr = message.mod_ref();
+  assert(msg_ptr != NULL);
+  assert(g_eventQueue_ptr->getTime() >= msg_ptr->getLastEnqueueTime());  // ensure we aren't dequeued early
+  msg_ptr->setDelayedCycles((g_eventQueue_ptr->getTime() - msg_ptr->getLastEnqueueTime())+msg_ptr->getDelayedCycles());
+  msg_ptr->setLastEnqueueTime(arrival_time);
+
+  // Insert the message into the priority heap
+  MessageBufferNode thisNode(arrival_time, m_msg_counter, message);
+  m_prio_heap.insert(thisNode);
+
+  DEBUG_NEWLINE(QUEUE_COMP,HighPrio);
+  DEBUG_MSG(QUEUE_COMP,HighPrio,"enqueue " + m_name
+            + " with arrival_time " + int_to_string(arrival_time)
+            + " cur_time: " + int_to_string(g_eventQueue_ptr->getTime()) + ".");
+  DEBUG_EXPR(QUEUE_COMP,MedPrio,message);
+  DEBUG_NEWLINE(QUEUE_COMP,HighPrio);
+
+  // Schedule the wakeup
+  if (m_consumer_ptr != NULL) {
+    g_eventQueue_ptr->scheduleEventAbsolute(m_consumer_ptr, arrival_time);
+  } else {
+    WARN_EXPR(*this);
+    WARN_EXPR(m_name);
+    ERROR_MSG("No consumer");
+  }
+}
+
+int MessageBuffer::dequeue_getDelayCycles(MsgPtr& message)
+{
+  int delay_cycles = -1;  // null value
+
+  dequeue(message);
+
+  // get the delay cycles
+  delay_cycles = setAndReturnDelayCycles(message);
+
+  assert(delay_cycles >= 0);
+  return delay_cycles;
+}
+
+void MessageBuffer::dequeue(MsgPtr& message)
+{
+  DEBUG_MSG(QUEUE_COMP,MedPrio,"dequeue from " + m_name);
+  message = m_prio_heap.peekMin().m_msgptr;
+
+  pop();
+  DEBUG_EXPR(QUEUE_COMP,MedPrio,message);
+}
+
+int MessageBuffer::dequeue_getDelayCycles()
+{
+  int delay_cycles = -1;  // null value
+
+  // get MsgPtr of the message about to be dequeued
+  MsgPtr message = m_prio_heap.peekMin().m_msgptr;
+
+  // get the delay cycles
+  delay_cycles = setAndReturnDelayCycles(message);
+
+  dequeue();
+
+  assert(delay_cycles >= 0);
+  return delay_cycles;
+}
+
+void MessageBuffer::pop()
+{
+  DEBUG_MSG(QUEUE_COMP,MedPrio,"pop from " + m_name);
+  assert(isReady());
+  Time ready_time = m_prio_heap.extractMin().m_time;
+  // record previous size and time so the current buffer size isn't adjusted until next cycle
+  if (m_time_last_time_pop < g_eventQueue_ptr->getTime()) {
+    m_size_at_cycle_start = m_size;
+    m_time_last_time_pop = g_eventQueue_ptr->getTime();
+  }
+  m_size--;
+}
+
+void MessageBuffer::clear()
+{
+  while(m_prio_heap.size() > 0){
+    m_prio_heap.extractMin();
+  }
+
+  ASSERT(m_prio_heap.size() == 0);
+
+  m_msg_counter = 0;
+  m_size = 0;
+  m_time_last_time_enqueue = 0;
+  m_time_last_time_pop = 0;
+  m_size_at_cycle_start = 0;
+  m_msgs_this_cycle = 0;
+}
+
+void MessageBuffer::recycle()
+{
+  //  const int RECYCLE_LATENCY = 3;
+  DEBUG_MSG(QUEUE_COMP,MedPrio,"recycling " + m_name);
+  assert(isReady());
+  MessageBufferNode node = m_prio_heap.extractMin();
+  node.m_time = g_eventQueue_ptr->getTime() + RECYCLE_LATENCY;
+  m_prio_heap.insert(node);
+  g_eventQueue_ptr->scheduleEventAbsolute(m_consumer_ptr, g_eventQueue_ptr->getTime() + RECYCLE_LATENCY);
+}
+
+int MessageBuffer::setAndReturnDelayCycles(MsgPtr& message)
+{
+  int delay_cycles = -1;  // null value
+
+  // get the delay cycles of the message at the top of the queue
+  Message* msg_ptr = message.ref();
+
+  // this function should only be called on dequeue
+  // ensure the msg hasn't been enqueued
+  assert(msg_ptr->getLastEnqueueTime() <= g_eventQueue_ptr->getTime());
+  msg_ptr->setDelayedCycles((g_eventQueue_ptr->getTime() - msg_ptr->getLastEnqueueTime())+msg_ptr->getDelayedCycles());
+  delay_cycles = msg_ptr->getDelayedCycles();
+
+  assert(delay_cycles >= 0);
+  return delay_cycles;
+}
+
+void MessageBuffer::print(ostream& out) const
+{
+  out << "[MessageBuffer: ";
+  if (m_consumer_ptr != NULL) {
+    out << " consumer-yes ";
+  }
+  out << m_prio_heap << "] " << m_name << endl;
+}
+
+void MessageBuffer::printStats(ostream& out)
+{
+  out << "MessageBuffer: " << m_name << " stats - msgs:" << m_msg_counter << " full:" << m_not_avail_count << endl;
+}
+
diff --git a/src/mem/ruby/buffers/MessageBuffer.hh b/src/mem/ruby/buffers/MessageBuffer.hh
new file mode 100644
index 000000000..6851423c3
--- /dev/null
+++ b/src/mem/ruby/buffers/MessageBuffer.hh
@@ -0,0 +1,156 @@
+
+/*
+ * Copyright (c) 1999-2008 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.
+ */
+
+/*
+ * $Id$
+ *
+ * Description: Unordered buffer of messages that can be inserted such
+ * that they can be dequeued after a given delta time has expired.
+ *
+ */
+
+#ifndef MESSAGEBUFFER_H
+#define MESSAGEBUFFER_H
+
+#include "Global.hh"
+#include "MessageBufferNode.hh"
+#include "Consumer.hh"
+#include "EventQueue.hh"
+#include "Message.hh"
+#include "PrioHeap.hh"
+#include "util.hh"
+
+class Chip;
+
+class MessageBuffer {
+public:
+  // Constructors
+  MessageBuffer();
+  MessageBuffer(const Chip* chip_ptr); // The chip_ptr is ignored, but could be used for extra debugging
+
+  // Use Default Destructor
+  // ~MessageBuffer()
+
+  // Public Methods
+
+  static void printConfig(ostream& out) {}
+
+  // TRUE if head of queue timestamp <= SystemTime
+  bool isReady() const {
+    return ((m_prio_heap.size() > 0) &&
+            (m_prio_heap.peekMin().m_time <= g_eventQueue_ptr->getTime()));
+  }
+
+  bool areNSlotsAvailable(int n);
+  int getPriority() { return m_priority_rank; }
+  void setPriority(int rank) { m_priority_rank = rank; }
+  void setConsumer(Consumer* consumer_ptr) { ASSERT(m_consumer_ptr==NULL); m_consumer_ptr = consumer_ptr; }
+  void setDescription(const string& name) { m_name = name; }
+  string getDescription() { return m_name;}
+
+  Consumer* getConsumer() { return m_consumer_ptr; }
+
+  const Message* peekAtHeadOfQueue() const;
+  const Message* peek() const { return peekAtHeadOfQueue(); }
+  const MsgPtr getMsgPtrCopy() const;
+  const MsgPtr& peekMsgPtr() const { assert(isReady()); return m_prio_heap.peekMin().m_msgptr; }
+  const MsgPtr& peekMsgPtrEvenIfNotReady() const {return m_prio_heap.peekMin().m_msgptr; }
+
+  void enqueue(const MsgPtr& message) { enqueue(message, 1); }
+  void enqueue(const MsgPtr& message, Time delta);
+  //  void enqueueAbsolute(const MsgPtr& message, Time absolute_time);
+  int dequeue_getDelayCycles(MsgPtr& message);  // returns delay cycles of the message
+  void dequeue(MsgPtr& message);
+  int dequeue_getDelayCycles();  // returns delay cycles of the message
+  void dequeue() { pop(); }
+  void pop();
+  void recycle();
+  bool isEmpty() const { return m_prio_heap.size() == 0; }
+
+  void setOrdering(bool order) { m_strict_fifo = order; m_ordering_set = true; }
+  void setSize(int size) {m_max_size = size;}
+  int getSize();
+  void setRandomization(bool random_flag) { m_randomization = random_flag; }
+
+  void clear();
+
+  void print(ostream& out) const;
+  void printStats(ostream& out);
+  void clearStats() { m_not_avail_count = 0; m_msg_counter = 0; }
+
+private:
+  // Private Methods
+  int setAndReturnDelayCycles(MsgPtr& message);
+
+  // Private copy constructor and assignment operator
+  MessageBuffer(const MessageBuffer& obj);
+  MessageBuffer& operator=(const MessageBuffer& obj);
+
+  // Data Members (m_ prefix)
+  Consumer* m_consumer_ptr;  // Consumer to signal a wakeup(), can be NULL
+  PrioHeap<MessageBufferNode> m_prio_heap;
+  string m_name;
+
+  int m_max_size;
+  int m_size;
+
+  Time m_time_last_time_size_checked;
+  int m_size_last_time_size_checked;
+
+  // variables used so enqueues appear to happen imediately, while pop happen the next cycle
+  Time m_time_last_time_enqueue;
+  Time m_time_last_time_pop;
+  int m_size_at_cycle_start;
+  int m_msgs_this_cycle;
+
+  int m_not_avail_count;  // count the # of times I didn't have N slots available
+  int m_msg_counter;
+  int m_priority_rank;
+  bool m_strict_fifo;
+  bool m_ordering_set;
+  bool m_randomization;
+  Time m_last_arrival_time;
+};
+
+// Output operator declaration
+//template <class TYPE>
+ostream& operator<<(ostream& out, const MessageBuffer& obj);
+
+// ******************* Definitions *******************
+
+// Output operator definition
+extern inline
+ostream& operator<<(ostream& out, const MessageBuffer& obj)
+{
+  obj.print(out);
+  out << flush;
+  return out;
+}
+
+#endif //MESSAGEBUFFER_H
diff --git a/src/mem/ruby/buffers/MessageBufferNode.cc b/src/mem/ruby/buffers/MessageBufferNode.cc
new file mode 100644
index 000000000..c84347a38
--- /dev/null
+++ b/src/mem/ruby/buffers/MessageBufferNode.cc
@@ -0,0 +1,48 @@
+
+/*
+ * Copyright (c) 1999-2008 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.
+ */
+
+/*
+ * EventQueueNode.C
+ *
+ * Description: See EventQueueNode.h
+ *
+ * $Id: MessageBufferNode.C,v 3.1 2001/02/02 16:57:54 sorin Exp $
+ *
+ */
+
+#include "MessageBufferNode.hh"
+
+void MessageBufferNode::print(ostream& out) const
+{
+  out << "[";
+  out << m_time << ", ";
+  out << m_msg_counter << ", ";
+  out << m_msgptr << "; ";
+  out << "]";
+}
diff --git a/src/mem/ruby/buffers/MessageBufferNode.hh b/src/mem/ruby/buffers/MessageBufferNode.hh
new file mode 100644
index 000000000..c562c45eb
--- /dev/null
+++ b/src/mem/ruby/buffers/MessageBufferNode.hh
@@ -0,0 +1,88 @@
+
+/*
+ * Copyright (c) 1999-2008 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.
+ */
+
+#ifndef MESSAGEBUFFERNODE_H
+#define MESSAGEBUFFERNODE_H
+
+#include "Global.hh"
+#include "Message.hh"
+
+class MessageBufferNode {
+public:
+  // Constructors
+  MessageBufferNode() { m_time = 0; m_msg_counter = 0; }
+  MessageBufferNode(const Time& time, int counter, const MsgPtr& msgptr)
+    { m_time = time; m_msgptr = msgptr; m_msg_counter = counter; }
+  // Destructor
+  //~MessageBufferNode();
+
+  // Public Methods
+  void print(ostream& out) const;
+private:
+  // Private Methods
+
+  // Default copy constructor and assignment operator
+  // MessageBufferNode(const MessageBufferNode& obj);
+  // MessageBufferNode& operator=(const MessageBufferNode& obj);
+
+  // Data Members (m_ prefix)
+public:
+  Time m_time;
+  int m_msg_counter; // FIXME, should this be a 64-bit value?
+  MsgPtr m_msgptr;
+};
+
+// Output operator declaration
+ostream& operator<<(ostream& out, const MessageBufferNode& obj);
+
+// ******************* Definitions *******************
+
+inline extern bool node_less_then_eq(const MessageBufferNode& n1, const MessageBufferNode& n2);
+
+inline extern
+bool node_less_then_eq(const MessageBufferNode& n1, const MessageBufferNode& n2)
+{
+  if (n1.m_time == n2.m_time) {
+    assert(n1.m_msg_counter != n2.m_msg_counter);
+    return (n1.m_msg_counter <= n2.m_msg_counter);
+  } else {
+    return (n1.m_time <= n2.m_time);
+  }
+}
+
+// Output operator definition
+extern inline
+ostream& operator<<(ostream& out, const MessageBufferNode& obj)
+{
+  obj.print(out);
+  out << flush;
+  return out;
+}
+
+#endif //MESSAGEBUFFERNODE_H