src/mem/ruby/network/MessageBuffer.cc - public/gem5 - Git at Google

 /*
  * Copyright (c) 2019-2021 ARM Limited
  * All rights reserved.
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * 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.
  */

 #include "mem/ruby/network/MessageBuffer.hh"

 #include <cassert>

 #include "base/cprintf.hh"
 #include "base/logging.hh"
 #include "base/random.hh"
 #include "base/stl_helpers.hh"
 #include "debug/RubyQueue.hh"
 #include "mem/ruby/system/RubySystem.hh"

 namespace gem5
 {

 namespace ruby
 {

 using stl_helpers::operator<<;

 MessageBuffer::MessageBuffer(const Params &p)
     : SimObject(p), m_stall_map_size(0),
     m_max_size(p.buffer_size), m_time_last_time_size_checked(0),
     m_time_last_time_enqueue(0), m_time_last_time_pop(0),
     m_last_arrival_time(0), m_strict_fifo(p.ordered),
     m_randomization(p.randomization),
     m_allow_zero_latency(p.allow_zero_latency),
     ADD_STAT(m_not_avail_count, "Number of times this buffer did not have "
                                 "N slots available"),
     ADD_STAT(m_buf_msgs, "Average number of messages in buffer"),
     ADD_STAT(m_stall_time, "Average number of cycles messages are stalled in "
                            "this MB"),
     ADD_STAT(m_stall_count, "Number of times messages were stalled"),
     ADD_STAT(m_occupancy, "Average occupancy of buffer capacity")
 {
     m_msg_counter = 0;
     m_consumer = NULL;
     m_size_last_time_size_checked = 0;
     m_size_at_cycle_start = 0;
     m_stalled_at_cycle_start = 0;
     m_msgs_this_cycle = 0;
     m_priority_rank = 0;

     m_stall_msg_map.clear();
     m_input_link_id = 0;
     m_vnet_id = 0;

     m_buf_msgs = 0;
     m_stall_time = 0;

     m_dequeue_callback = nullptr;

     // stats
     m_not_avail_count
         .flags(statistics::nozero);

     m_buf_msgs
         .flags(statistics::nozero);

     m_stall_count
         .flags(statistics::nozero);

     m_occupancy
         .flags(statistics::nozero);

     m_stall_time
         .flags(statistics::nozero);

     if (m_max_size > 0) {
         m_occupancy = m_buf_msgs / m_max_size;
     } else {
         m_occupancy = 0;
     }
 }

 unsigned int
 MessageBuffer::getSize(Tick curTime)
 {
     if (m_time_last_time_size_checked != curTime) {
         m_time_last_time_size_checked = curTime;
         m_size_last_time_size_checked = m_prio_heap.size();
     }

     return m_size_last_time_size_checked;
 }

 bool
 MessageBuffer::areNSlotsAvailable(unsigned int n, Tick current_time)
 {

     // fast path when message buffers have infinite size
     if (m_max_size == 0) {
         return true;
     }

     // determine the correct size for the current cycle
     // pop operations shouldn't effect the network's visible size
     // until schd cycle, but enqueue operations effect the visible
     // size immediately
     unsigned int current_size = 0;
     unsigned int current_stall_size = 0;

     if (m_time_last_time_pop < current_time) {
         // no pops this cycle - heap and stall queue size is correct
         current_size = m_prio_heap.size();
         current_stall_size = m_stall_map_size;
     } else {
         if (m_time_last_time_enqueue < current_time) {
             // 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;
         }

         // Stall queue size at start is considered
         current_stall_size = m_stalled_at_cycle_start;
     }

     // now compare the new size with our max size
     if (current_size + current_stall_size + n <= m_max_size) {
         return true;
     } else {
         DPRINTF(RubyQueue, "n: %d, current_size: %d, heap size: %d, "
                 "m_max_size: %d\n",
                 n, current_size + current_stall_size,
                 m_prio_heap.size(), m_max_size);
         m_not_avail_count++;
         return false;
     }
 }

 const Message*
 MessageBuffer::peek() const
 {
     DPRINTF(RubyQueue, "Peeking at head of queue.\n");
     const Message* msg_ptr = m_prio_heap.front().get();
     assert(msg_ptr);

     DPRINTF(RubyQueue, "Message: %s\n", (*msg_ptr));
     return msg_ptr;
 }

 // FIXME - move me somewhere else
 Tick
 random_time()
 {
     Tick time = 1;
     time += random_mt.random(0, 3);  // [0...3]
     if (random_mt.random(0, 7) == 0) {  // 1 in 8 chance
         time += 100 + random_mt.random(1, 15); // 100 + [1...15]
     }
     return time;
 }

 void
 MessageBuffer::enqueue(MsgPtr message, Tick current_time, Tick delta)
 {
     // record current time incase we have a pop that also adjusts my size
     if (m_time_last_time_enqueue < current_time) {
         m_msgs_this_cycle = 0;  // first msg this cycle
         m_time_last_time_enqueue = current_time;
     }

     m_msg_counter++;
     m_msgs_this_cycle++;

     // Calculate the arrival time of the message, that is, the first
     // cycle the message can be dequeued.
     panic_if((delta == 0) && !m_allow_zero_latency,
            "Delta equals zero and allow_zero_latency is false during enqueue");
     Tick arrival_time = 0;

     // random delays are inserted if the RubySystem level randomization flag
     // is turned on and this buffer allows it
     if ((m_randomization == MessageRandomization::disabled) ||
         ((m_randomization == MessageRandomization::ruby_system) &&
           !RubySystem::getRandomization())) {
         // 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) {
             panic("FIFO ordering violated: %s name: %s current time: %d "
                   "delta: %d arrival_time: %d last arrival_time: %d\n",
                   *this, name(), current_time, delta, arrival_time,
                   m_last_arrival_time);
         }
     }

     // If running a cache trace, don't worry about the last arrival checks
     if (!RubySystem::getWarmupEnabled()) {
         m_last_arrival_time = arrival_time;
     }

     // compute the delay cycles and set enqueue time
     Message* msg_ptr = message.get();
     assert(msg_ptr != NULL);

     assert(current_time >= msg_ptr->getLastEnqueueTime() &&
            "ensure we aren't dequeued early");

     msg_ptr->updateDelayedTicks(current_time);
     msg_ptr->setLastEnqueueTime(arrival_time);
     msg_ptr->setMsgCounter(m_msg_counter);

     // Insert the message into the priority heap
     m_prio_heap.push_back(message);
     push_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());
     // Increment the number of messages statistic
     m_buf_msgs++;

     assert((m_max_size == 0) ||
            ((m_prio_heap.size() + m_stall_map_size) <= m_max_size));

     DPRINTF(RubyQueue, "Enqueue arrival_time: %lld, Message: %s\n",
             arrival_time, *(message.get()));

     // Schedule the wakeup
     assert(m_consumer != NULL);
     m_consumer->scheduleEventAbsolute(arrival_time);
     m_consumer->storeEventInfo(m_vnet_id);
 }

 Tick
 MessageBuffer::dequeue(Tick current_time, bool decrement_messages)
 {
     DPRINTF(RubyQueue, "Popping\n");
     assert(isReady(current_time));

     // get MsgPtr of the message about to be dequeued
     MsgPtr message = m_prio_heap.front();

     // get the delay cycles
     message->updateDelayedTicks(current_time);
     Tick delay = message->getDelayedTicks();

     m_stall_time = curTick() - message->getTime();

     // record previous size and time so the current buffer size isn't
     // adjusted until schd cycle
     if (m_time_last_time_pop < current_time) {
         m_size_at_cycle_start = m_prio_heap.size();
         m_stalled_at_cycle_start = m_stall_map_size;
         m_time_last_time_pop = current_time;
     }

     pop_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());
     m_prio_heap.pop_back();
     if (decrement_messages) {
         // If the message will be removed from the queue, decrement the
         // number of message in the queue.
         m_buf_msgs--;
     }

     // if a dequeue callback was requested, call it now
     if (m_dequeue_callback) {
         m_dequeue_callback();
     }

     return delay;
 }

 void
 MessageBuffer::registerDequeueCallback(std::function<void()> callback)
 {
     m_dequeue_callback = callback;
 }

 void
 MessageBuffer::unregisterDequeueCallback()
 {
     m_dequeue_callback = nullptr;
 }

 void
 MessageBuffer::clear()
 {
     m_prio_heap.clear();

     m_msg_counter = 0;
     m_time_last_time_enqueue = 0;
     m_time_last_time_pop = 0;
     m_size_at_cycle_start = 0;
     m_stalled_at_cycle_start = 0;
     m_msgs_this_cycle = 0;
 }

 void
 MessageBuffer::recycle(Tick current_time, Tick recycle_latency)
 {
     DPRINTF(RubyQueue, "Recycling.\n");
     assert(isReady(current_time));
     MsgPtr node = m_prio_heap.front();
     pop_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());

     Tick future_time = current_time + recycle_latency;
     node->setLastEnqueueTime(future_time);

     m_prio_heap.back() = node;
     push_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());
     m_consumer->scheduleEventAbsolute(future_time);
 }

 void
 MessageBuffer::reanalyzeList(std::list<MsgPtr> &lt, Tick schdTick)
 {
     while (!lt.empty()) {
         MsgPtr m = lt.front();
         assert(m->getLastEnqueueTime() <= schdTick);

         m_prio_heap.push_back(m);
         push_heap(m_prio_heap.begin(), m_prio_heap.end(),
                   std::greater<MsgPtr>());

         m_consumer->scheduleEventAbsolute(schdTick);

         DPRINTF(RubyQueue, "Requeue arrival_time: %lld, Message: %s\n",
             schdTick, *(m.get()));

         lt.pop_front();
     }
 }

 void
 MessageBuffer::reanalyzeMessages(Addr addr, Tick current_time)
 {
     DPRINTF(RubyQueue, "ReanalyzeMessages %#x\n", addr);
     assert(m_stall_msg_map.count(addr) > 0);

     //
     // Put all stalled messages associated with this address back on the
     // prio heap.  The reanalyzeList call will make sure the consumer is
     // scheduled for the current cycle so that the previously stalled messages
     // will be observed before any younger messages that may arrive this cycle
     //
     m_stall_map_size -= m_stall_msg_map[addr].size();
     assert(m_stall_map_size >= 0);
     reanalyzeList(m_stall_msg_map[addr], current_time);
     m_stall_msg_map.erase(addr);
 }

 void
 MessageBuffer::reanalyzeAllMessages(Tick current_time)
 {
     DPRINTF(RubyQueue, "ReanalyzeAllMessages\n");

     //
     // Put all stalled messages associated with this address back on the
     // prio heap.  The reanalyzeList call will make sure the consumer is
     // scheduled for the current cycle so that the previously stalled messages
     // will be observed before any younger messages that may arrive this cycle.
     //
     for (StallMsgMapType::iterator map_iter = m_stall_msg_map.begin();
          map_iter != m_stall_msg_map.end(); ++map_iter) {
         m_stall_map_size -= map_iter->second.size();
         assert(m_stall_map_size >= 0);
         reanalyzeList(map_iter->second, current_time);
     }
     m_stall_msg_map.clear();
 }

 void
 MessageBuffer::stallMessage(Addr addr, Tick current_time)
 {
     DPRINTF(RubyQueue, "Stalling due to %#x\n", addr);
     assert(isReady(current_time));
     assert(getOffset(addr) == 0);
     MsgPtr message = m_prio_heap.front();

     // Since the message will just be moved to stall map, indicate that the
     // buffer should not decrement the m_buf_msgs statistic
     dequeue(current_time, false);

     //
     // Note: no event is scheduled to analyze the map at a later time.
     // Instead the controller is responsible to call reanalyzeMessages when
     // these addresses change state.
     //
     (m_stall_msg_map[addr]).push_back(message);
     m_stall_map_size++;
     m_stall_count++;
 }

 bool
 MessageBuffer::hasStalledMsg(Addr addr) const
 {
     return (m_stall_msg_map.count(addr) != 0);
 }

 void
 MessageBuffer::deferEnqueueingMessage(Addr addr, MsgPtr message)
 {
     DPRINTF(RubyQueue, "Deferring enqueueing message: %s, Address %#x\n",
             *(message.get()), addr);
     (m_deferred_msg_map[addr]).push_back(message);
 }

 void
 MessageBuffer::enqueueDeferredMessages(Addr addr, Tick curTime, Tick delay)
 {
     assert(!isDeferredMsgMapEmpty(addr));
     std::vector<MsgPtr>& msg_vec = m_deferred_msg_map[addr];
     assert(msg_vec.size() > 0);

     // enqueue all deferred messages associated with this address
     for (MsgPtr m : msg_vec) {
         enqueue(m, curTime, delay);
     }

     msg_vec.clear();
     m_deferred_msg_map.erase(addr);
 }

 bool
 MessageBuffer::isDeferredMsgMapEmpty(Addr addr) const
 {
     return m_deferred_msg_map.count(addr) == 0;
 }

 void
 MessageBuffer::print(std::ostream& out) const
 {
     ccprintf(out, "[MessageBuffer: ");
     if (m_consumer != NULL) {
         ccprintf(out, " consumer-yes ");
     }

     std::vector<MsgPtr> copy(m_prio_heap);
     std::sort_heap(copy.begin(), copy.end(), std::greater<MsgPtr>());
     ccprintf(out, "%s] %s", copy, name());
 }

 bool
 MessageBuffer::isReady(Tick current_time) const
 {
     return ((m_prio_heap.size() > 0) &&
         (m_prio_heap.front()->getLastEnqueueTime() <= current_time));
 }

 uint32_t
 MessageBuffer::functionalAccess(Packet *pkt, bool is_read, WriteMask *mask)
 {
     DPRINTF(RubyQueue, "functional %s for %#x\n",
             is_read ? "read" : "write", pkt->getAddr());

     uint32_t num_functional_accesses = 0;

     // Check the priority heap and write any messages that may
     // correspond to the address in the packet.
     for (unsigned int i = 0; i < m_prio_heap.size(); ++i) {
         Message *msg = m_prio_heap[i].get();
         if (is_read && !mask && msg->functionalRead(pkt))
             return 1;
         else if (is_read && mask && msg->functionalRead(pkt, *mask))
             num_functional_accesses++;
         else if (!is_read && msg->functionalWrite(pkt))
             num_functional_accesses++;
     }

     // Check the stall queue and write any messages that may
     // correspond to the address in the packet.
     for (StallMsgMapType::iterator map_iter = m_stall_msg_map.begin();
          map_iter != m_stall_msg_map.end();
          ++map_iter) {

         for (std::list<MsgPtr>::iterator it = (map_iter->second).begin();
             it != (map_iter->second).end(); ++it) {

             Message *msg = (*it).get();
             if (is_read && !mask && msg->functionalRead(pkt))
                 return 1;
             else if (is_read && mask && msg->functionalRead(pkt, *mask))
                 num_functional_accesses++;
             else if (!is_read && msg->functionalWrite(pkt))
                 num_functional_accesses++;
         }
     }

     return num_functional_accesses;
 }

 } // namespace ruby
 } // namespace gem5
	/*
	* Copyright (c) 2019-2021 ARM Limited
	* All rights reserved.
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* 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.
	*/

	#include "mem/ruby/network/MessageBuffer.hh"

	#include <cassert>

	#include "base/cprintf.hh"
	#include "base/logging.hh"
	#include "base/random.hh"
	#include "base/stl_helpers.hh"
	#include "debug/RubyQueue.hh"
	#include "mem/ruby/system/RubySystem.hh"

	namespace gem5
	{

	namespace ruby
	{

	using stl_helpers::operator<<;

	MessageBuffer::MessageBuffer(const Params &p)
	: SimObject(p), m_stall_map_size(0),
	m_max_size(p.buffer_size), m_time_last_time_size_checked(0),
	m_time_last_time_enqueue(0), m_time_last_time_pop(0),
	m_last_arrival_time(0), m_strict_fifo(p.ordered),
	m_randomization(p.randomization),
	m_allow_zero_latency(p.allow_zero_latency),
	ADD_STAT(m_not_avail_count, "Number of times this buffer did not have "
	"N slots available"),
	ADD_STAT(m_buf_msgs, "Average number of messages in buffer"),
	ADD_STAT(m_stall_time, "Average number of cycles messages are stalled in "
	"this MB"),
	ADD_STAT(m_stall_count, "Number of times messages were stalled"),
	ADD_STAT(m_occupancy, "Average occupancy of buffer capacity")
	{
	m_msg_counter = 0;
	m_consumer = NULL;
	m_size_last_time_size_checked = 0;
	m_size_at_cycle_start = 0;
	m_stalled_at_cycle_start = 0;
	m_msgs_this_cycle = 0;
	m_priority_rank = 0;

	m_stall_msg_map.clear();
	m_input_link_id = 0;
	m_vnet_id = 0;

	m_buf_msgs = 0;
	m_stall_time = 0;

	m_dequeue_callback = nullptr;

	// stats
	m_not_avail_count
	.flags(statistics::nozero);

	m_buf_msgs
	.flags(statistics::nozero);

	m_stall_count
	.flags(statistics::nozero);

	m_occupancy
	.flags(statistics::nozero);

	m_stall_time
	.flags(statistics::nozero);

	if (m_max_size > 0) {
	m_occupancy = m_buf_msgs / m_max_size;
	} else {
	m_occupancy = 0;
	}
	}

	unsigned int
	MessageBuffer::getSize(Tick curTime)
	{
	if (m_time_last_time_size_checked != curTime) {
	m_time_last_time_size_checked = curTime;
	m_size_last_time_size_checked = m_prio_heap.size();
	}

	return m_size_last_time_size_checked;
	}

	bool
	MessageBuffer::areNSlotsAvailable(unsigned int n, Tick current_time)
	{

	// fast path when message buffers have infinite size
	if (m_max_size == 0) {
	return true;
	}

	// determine the correct size for the current cycle
	// pop operations shouldn't effect the network's visible size
	// until schd cycle, but enqueue operations effect the visible
	// size immediately
	unsigned int current_size = 0;
	unsigned int current_stall_size = 0;

	if (m_time_last_time_pop < current_time) {
	// no pops this cycle - heap and stall queue size is correct
	current_size = m_prio_heap.size();
	current_stall_size = m_stall_map_size;
	} else {
	if (m_time_last_time_enqueue < current_time) {
	// 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;
	}

	// Stall queue size at start is considered
	current_stall_size = m_stalled_at_cycle_start;
	}

	// now compare the new size with our max size
	if (current_size + current_stall_size + n <= m_max_size) {
	return true;
	} else {
	DPRINTF(RubyQueue, "n: %d, current_size: %d, heap size: %d, "
	"m_max_size: %d\n",
	n, current_size + current_stall_size,
	m_prio_heap.size(), m_max_size);
	m_not_avail_count++;
	return false;
	}
	}

	const Message*
	MessageBuffer::peek() const
	{
	DPRINTF(RubyQueue, "Peeking at head of queue.\n");
	const Message* msg_ptr = m_prio_heap.front().get();
	assert(msg_ptr);

	DPRINTF(RubyQueue, "Message: %s\n", (*msg_ptr));
	return msg_ptr;
	}

	// FIXME - move me somewhere else
	Tick
	random_time()
	{
	Tick time = 1;
	time += random_mt.random(0, 3); // [0...3]
	if (random_mt.random(0, 7) == 0) { // 1 in 8 chance
	time += 100 + random_mt.random(1, 15); // 100 + [1...15]
	}
	return time;
	}

	void
	MessageBuffer::enqueue(MsgPtr message, Tick current_time, Tick delta)
	{
	// record current time incase we have a pop that also adjusts my size
	if (m_time_last_time_enqueue < current_time) {
	m_msgs_this_cycle = 0; // first msg this cycle
	m_time_last_time_enqueue = current_time;
	}

	m_msg_counter++;
	m_msgs_this_cycle++;

	// Calculate the arrival time of the message, that is, the first
	// cycle the message can be dequeued.
	panic_if((delta == 0) && !m_allow_zero_latency,
	"Delta equals zero and allow_zero_latency is false during enqueue");
	Tick arrival_time = 0;

	// random delays are inserted if the RubySystem level randomization flag
	// is turned on and this buffer allows it
	if ((m_randomization == MessageRandomization::disabled) \|\|
	((m_randomization == MessageRandomization::ruby_system) &&
	!RubySystem::getRandomization())) {
	// 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) {
	panic("FIFO ordering violated: %s name: %s current time: %d "
	"delta: %d arrival_time: %d last arrival_time: %d\n",
	*this, name(), current_time, delta, arrival_time,
	m_last_arrival_time);
	}
	}

	// If running a cache trace, don't worry about the last arrival checks
	if (!RubySystem::getWarmupEnabled()) {
	m_last_arrival_time = arrival_time;
	}

	// compute the delay cycles and set enqueue time
	Message* msg_ptr = message.get();
	assert(msg_ptr != NULL);

	assert(current_time >= msg_ptr->getLastEnqueueTime() &&
	"ensure we aren't dequeued early");

	msg_ptr->updateDelayedTicks(current_time);
	msg_ptr->setLastEnqueueTime(arrival_time);
	msg_ptr->setMsgCounter(m_msg_counter);

	// Insert the message into the priority heap
	m_prio_heap.push_back(message);
	push_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());
	// Increment the number of messages statistic
	m_buf_msgs++;

	assert((m_max_size == 0) \|\|
	((m_prio_heap.size() + m_stall_map_size) <= m_max_size));

	DPRINTF(RubyQueue, "Enqueue arrival_time: %lld, Message: %s\n",
	arrival_time, *(message.get()));

	// Schedule the wakeup
	assert(m_consumer != NULL);
	m_consumer->scheduleEventAbsolute(arrival_time);
	m_consumer->storeEventInfo(m_vnet_id);
	}

	Tick
	MessageBuffer::dequeue(Tick current_time, bool decrement_messages)
	{
	DPRINTF(RubyQueue, "Popping\n");
	assert(isReady(current_time));

	// get MsgPtr of the message about to be dequeued
	MsgPtr message = m_prio_heap.front();

	// get the delay cycles
	message->updateDelayedTicks(current_time);
	Tick delay = message->getDelayedTicks();

	m_stall_time = curTick() - message->getTime();

	// record previous size and time so the current buffer size isn't
	// adjusted until schd cycle
	if (m_time_last_time_pop < current_time) {
	m_size_at_cycle_start = m_prio_heap.size();
	m_stalled_at_cycle_start = m_stall_map_size;
	m_time_last_time_pop = current_time;
	}

	pop_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());
	m_prio_heap.pop_back();
	if (decrement_messages) {
	// If the message will be removed from the queue, decrement the
	// number of message in the queue.
	m_buf_msgs--;
	}

	// if a dequeue callback was requested, call it now
	if (m_dequeue_callback) {
	m_dequeue_callback();
	}

	return delay;
	}

	void
	MessageBuffer::registerDequeueCallback(std::function<void()> callback)
	{
	m_dequeue_callback = callback;
	}

	void
	MessageBuffer::unregisterDequeueCallback()
	{
	m_dequeue_callback = nullptr;
	}

	void
	MessageBuffer::clear()
	{
	m_prio_heap.clear();

	m_msg_counter = 0;
	m_time_last_time_enqueue = 0;
	m_time_last_time_pop = 0;
	m_size_at_cycle_start = 0;
	m_stalled_at_cycle_start = 0;
	m_msgs_this_cycle = 0;
	}

	void
	MessageBuffer::recycle(Tick current_time, Tick recycle_latency)
	{
	DPRINTF(RubyQueue, "Recycling.\n");
	assert(isReady(current_time));
	MsgPtr node = m_prio_heap.front();
	pop_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());

	Tick future_time = current_time + recycle_latency;
	node->setLastEnqueueTime(future_time);

	m_prio_heap.back() = node;
	push_heap(m_prio_heap.begin(), m_prio_heap.end(), std::greater<MsgPtr>());
	m_consumer->scheduleEventAbsolute(future_time);
	}

	void
	MessageBuffer::reanalyzeList(std::list<MsgPtr> &lt, Tick schdTick)
	{
	while (!lt.empty()) {
	MsgPtr m = lt.front();
	assert(m->getLastEnqueueTime() <= schdTick);

	m_prio_heap.push_back(m);
	push_heap(m_prio_heap.begin(), m_prio_heap.end(),
	std::greater<MsgPtr>());

	m_consumer->scheduleEventAbsolute(schdTick);

	DPRINTF(RubyQueue, "Requeue arrival_time: %lld, Message: %s\n",
	schdTick, *(m.get()));

	lt.pop_front();
	}
	}

	void
	MessageBuffer::reanalyzeMessages(Addr addr, Tick current_time)
	{
	DPRINTF(RubyQueue, "ReanalyzeMessages %#x\n", addr);
	assert(m_stall_msg_map.count(addr) > 0);

	//
	// Put all stalled messages associated with this address back on the
	// prio heap. The reanalyzeList call will make sure the consumer is
	// scheduled for the current cycle so that the previously stalled messages
	// will be observed before any younger messages that may arrive this cycle
	//
	m_stall_map_size -= m_stall_msg_map[addr].size();
	assert(m_stall_map_size >= 0);
	reanalyzeList(m_stall_msg_map[addr], current_time);
	m_stall_msg_map.erase(addr);
	}

	void
	MessageBuffer::reanalyzeAllMessages(Tick current_time)
	{
	DPRINTF(RubyQueue, "ReanalyzeAllMessages\n");

	//
	// Put all stalled messages associated with this address back on the
	// prio heap. The reanalyzeList call will make sure the consumer is
	// scheduled for the current cycle so that the previously stalled messages
	// will be observed before any younger messages that may arrive this cycle.
	//
	for (StallMsgMapType::iterator map_iter = m_stall_msg_map.begin();
	map_iter != m_stall_msg_map.end(); ++map_iter) {
	m_stall_map_size -= map_iter->second.size();
	assert(m_stall_map_size >= 0);
	reanalyzeList(map_iter->second, current_time);
	}
	m_stall_msg_map.clear();
	}

	void
	MessageBuffer::stallMessage(Addr addr, Tick current_time)
	{
	DPRINTF(RubyQueue, "Stalling due to %#x\n", addr);
	assert(isReady(current_time));
	assert(getOffset(addr) == 0);
	MsgPtr message = m_prio_heap.front();

	// Since the message will just be moved to stall map, indicate that the
	// buffer should not decrement the m_buf_msgs statistic
	dequeue(current_time, false);

	//
	// Note: no event is scheduled to analyze the map at a later time.
	// Instead the controller is responsible to call reanalyzeMessages when
	// these addresses change state.
	//
	(m_stall_msg_map[addr]).push_back(message);
	m_stall_map_size++;
	m_stall_count++;
	}

	bool
	MessageBuffer::hasStalledMsg(Addr addr) const
	{
	return (m_stall_msg_map.count(addr) != 0);
	}

	void
	MessageBuffer::deferEnqueueingMessage(Addr addr, MsgPtr message)
	{
	DPRINTF(RubyQueue, "Deferring enqueueing message: %s, Address %#x\n",
	*(message.get()), addr);
	(m_deferred_msg_map[addr]).push_back(message);
	}

	void
	MessageBuffer::enqueueDeferredMessages(Addr addr, Tick curTime, Tick delay)
	{
	assert(!isDeferredMsgMapEmpty(addr));
	std::vector<MsgPtr>& msg_vec = m_deferred_msg_map[addr];
	assert(msg_vec.size() > 0);

	// enqueue all deferred messages associated with this address
	for (MsgPtr m : msg_vec) {
	enqueue(m, curTime, delay);
	}

	msg_vec.clear();
	m_deferred_msg_map.erase(addr);
	}

	bool
	MessageBuffer::isDeferredMsgMapEmpty(Addr addr) const
	{
	return m_deferred_msg_map.count(addr) == 0;
	}

	void
	MessageBuffer::print(std::ostream& out) const
	{
	ccprintf(out, "[MessageBuffer: ");
	if (m_consumer != NULL) {
	ccprintf(out, " consumer-yes ");
	}

	std::vector<MsgPtr> copy(m_prio_heap);
	std::sort_heap(copy.begin(), copy.end(), std::greater<MsgPtr>());
	ccprintf(out, "%s] %s", copy, name());
	}

	bool
	MessageBuffer::isReady(Tick current_time) const
	{
	return ((m_prio_heap.size() > 0) &&
	(m_prio_heap.front()->getLastEnqueueTime() <= current_time));
	}

	uint32_t
	MessageBuffer::functionalAccess(Packet pkt, bool is_read, WriteMask mask)
	{
	DPRINTF(RubyQueue, "functional %s for %#x\n",
	is_read ? "read" : "write", pkt->getAddr());

	uint32_t num_functional_accesses = 0;

	// Check the priority heap and write any messages that may
	// correspond to the address in the packet.
	for (unsigned int i = 0; i < m_prio_heap.size(); ++i) {
	Message *msg = m_prio_heap[i].get();
	if (is_read && !mask && msg->functionalRead(pkt))
	return 1;
	else if (is_read && mask && msg->functionalRead(pkt, *mask))
	num_functional_accesses++;
	else if (!is_read && msg->functionalWrite(pkt))
	num_functional_accesses++;
	}

	// Check the stall queue and write any messages that may
	// correspond to the address in the packet.
	for (StallMsgMapType::iterator map_iter = m_stall_msg_map.begin();
	map_iter != m_stall_msg_map.end();
	++map_iter) {

	for (std::list<MsgPtr>::iterator it = (map_iter->second).begin();
	it != (map_iter->second).end(); ++it) {

	Message msg = (it).get();
	if (is_read && !mask && msg->functionalRead(pkt))
	return 1;
	else if (is_read && mask && msg->functionalRead(pkt, *mask))
	num_functional_accesses++;
	else if (!is_read && msg->functionalWrite(pkt))
	num_functional_accesses++;
	}
	}

	return num_functional_accesses;
	}

	} // namespace ruby
	} // namespace gem5