TrafficGen: Add a basic traffic generator

This patch adds a traffic generator to the code base. The generator is
aimed to be used as a black box model to create appropriate use-cases
and benchmarks for the memory system, and in particular the
interconnect and the memory controller.

The traffic generator is a master module, where the actual behaviour
is captured in a state-transition graph where each state generates
some sort of traffic. By constructing a graph it is possible to create
very elaborate scenarios from basic generators. Currencly the set of
generators include idling, linear address sweeps, random address
sequences and playback of traces (recording will be done by the
Communication Monitor in a follow-up patch). At the moment the graph
and the states are described in an ad-hoc line-based format, and in
the future this should be aligned with our used of e.g. the Google
protobufs. Similarly for the traces, the format is currently a
simplistic ad-hoc line-based format that merely serves as a starting
point.

In addition to being used as a black-box model for system components,
the traffic generator is also useful for creating test cases and
regressions for the interconnect and memory system. In future patches
we will use the traffic generator to create DRAM test cases for the
controller model.

The patch following this one adds a basic regressions which also
contains an example configuration script and trace file for playback.

4 files changed, 1371 insertions, 0 deletions

diff --git a/src/cpu/testers/traffic_gen/SConscript b/src/cpu/testers/traffic_gen/SConscript
new file mode 100644
index 000000000..63ce20984
--- /dev/null
+++ b/src/cpu/testers/traffic_gen/SConscript
@@ -0,0 +1,46 @@
+# -*- mode:python -*-
+
+# Copyright (c) 2012 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.
+#
+# 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: Andreas Hansson
+
+Import('*')
+
+SimObject('TrafficGen.py')
+
+Source('traffic_gen.cc')
+
+DebugFlag('TrafficGen')
diff --git a/src/cpu/testers/traffic_gen/TrafficGen.py b/src/cpu/testers/traffic_gen/TrafficGen.py
new file mode 100644
index 000000000..15e9d7a9b
--- /dev/null
+++ b/src/cpu/testers/traffic_gen/TrafficGen.py
@@ -0,0 +1,72 @@
+# Copyright (c) 2012 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.
+#
+# 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: Thomas Grass
+#          Andreas Hansson
+#          Sascha Bischoff
+
+from m5.params import *
+from m5.proxy import *
+from MemObject import MemObject
+
+# The traffic generator is a master module that generates stimuli for
+# the memory system, based on a collection of simple behaviours that
+# are either probabilistic or based on traces. It can be used stand
+# alone for creating test cases for interconnect and memory
+# controllers, or function as a black-box replacement for system
+# components that are not yet modelled in detail, e.g. a video engine
+# or baseband subsystem in an SoC.
+#
+# The traffic generator has a single master port that is used to send
+# requests, independent of the specific behaviour. The behaviour of
+# the traffic generator is specified in a configuration file, and this
+# file describes a state transition graph where each state is a
+# specific generator behaviour. Examples include idling, generating
+# linear address sequences, random sequences and replay of captured
+# traces. By describing these behaviours as states, it is straight
+# forward to create very complex behaviours, simply by arranging them
+# in graphs. The graph transitions can also be annotated with
+# probabilities, effectively making it a Markov Chain.
+class TrafficGen(MemObject):
+    type = 'TrafficGen'
+
+    # Port used for sending requests and receiving responses
+    port = MasterPort("Master port")
+
+    # Config file to parse for the state descriptions
+    config_file = Param.String("Configuration file describing the behaviour")
+
+    # System used to determine the mode of the memory system
+    system = Param.System(Parent.any, "System this generator is part of")
diff --git a/src/cpu/testers/traffic_gen/traffic_gen.cc b/src/cpu/testers/traffic_gen/traffic_gen.cc
new file mode 100644
index 000000000..054900b20
--- /dev/null
+++ b/src/cpu/testers/traffic_gen/traffic_gen.cc
@@ -0,0 +1,638 @@
+/*
+ * Copyright (c) 2012 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.
+ *
+ * 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: Thomas Grass
+ *          Andreas Hansson
+ *          Sascha Bischoff
+ */
+
+#include <sstream>
+
+#include "base/random.hh"
+#include "cpu/testers/traffic_gen/traffic_gen.hh"
+#include "debug/Checkpoint.hh"
+#include "debug/TrafficGen.hh"
+#include "sim/stats.hh"
+#include "sim/system.hh"
+
+using namespace std;
+
+TrafficGen::TrafficGen(const TrafficGenParams* p)
+    : MemObject(p),
+      system(p->system),
+      masterID(system->getMasterId(name())),
+      port(name() + ".port", *this),
+      stateGraph(*this, port, p->config_file, masterID),
+      updateStateGraphEvent(this)
+{
+}
+
+TrafficGen*
+TrafficGenParams::create()
+{
+    return new TrafficGen(this);
+}
+
+MasterPort&
+TrafficGen::getMasterPort(const string& if_name, int idx)
+{
+    if (if_name == "port") {
+        return port;
+    } else {
+        return MemObject::getMasterPort(if_name, idx);
+    }
+}
+
+void
+TrafficGen::init()
+{
+    if (!port.isConnected())
+        fatal("The port of %s is not connected!\n", name());
+
+    Enums::MemoryMode mode = system->getMemoryMode();
+
+    // if the system is in timing mode active the request generator
+    if (mode == Enums::timing) {
+        DPRINTF(TrafficGen, "Timing mode, activating request generator\n");
+
+        // enter initial state
+        stateGraph.enterState(stateGraph.currState);
+    } else {
+        DPRINTF(TrafficGen,
+                "Traffic generator is only active in timing mode\n");
+    }
+}
+
+void
+TrafficGen::initState()
+{
+    // when not restoring from a checkpoint, make sure we kick things off
+    if (system->getMemoryMode() == Enums::timing) {
+        Tick nextStateGraphEvent = stateGraph.nextEventTick();
+        schedule(updateStateGraphEvent, nextStateGraphEvent);
+    } else {
+        DPRINTF(TrafficGen,
+                "Traffic generator is only active in timing mode\n");
+    }
+}
+
+unsigned int
+TrafficGen::drain(Event* drain_event)
+{
+    // @todo we should also stop putting new requests in the queue and
+    // either interrupt the current state or wait for a transition
+    return port.drain(drain_event);
+}
+
+void
+TrafficGen::serialize(ostream &os)
+{
+    DPRINTF(Checkpoint, "Serializing TrafficGen\n");
+
+    // save ticks of the graph event if it is scheduled
+    Tick nextStateGraphEvent = updateStateGraphEvent.scheduled() ?
+        updateStateGraphEvent.when() : 0;
+
+    DPRINTF(TrafficGen, "Saving nextStateGraphEvent=%llu\n",
+            nextStateGraphEvent);
+
+    SERIALIZE_SCALAR(nextStateGraphEvent);
+
+    Tick nextTransitionTick = stateGraph.nextTransitionTick;
+    SERIALIZE_SCALAR(nextTransitionTick);
+
+    // @todo: also serialise the current state, figure out the best
+    // way to drain and restore
+}
+
+void
+TrafficGen::unserialize(Checkpoint* cp, const string& section)
+{
+    // restore scheduled events
+    Tick nextStateGraphEvent;
+    UNSERIALIZE_SCALAR(nextStateGraphEvent);
+    if (nextStateGraphEvent != 0) {
+        schedule(updateStateGraphEvent, nextStateGraphEvent);
+    }
+
+    Tick nextTransitionTick;
+    UNSERIALIZE_SCALAR(nextTransitionTick);
+    stateGraph.nextTransitionTick = nextTransitionTick;
+}
+
+void
+TrafficGen::updateStateGraph()
+{
+    // schedule next update event based on either the next execute
+    // tick or the next transition, which ever comes first
+    Tick nextStateGraphEvent = stateGraph.nextEventTick();
+    DPRINTF(TrafficGen, "Updating state graph, next event at %lld\n",
+            nextStateGraphEvent);
+    schedule(updateStateGraphEvent, nextStateGraphEvent);
+
+    // perform the update associated with the current update event
+    stateGraph.update();
+}
+
+void
+TrafficGen::StateGraph::parseConfig(const string& file_name,
+                                    MasterID master_id)
+{
+    // keep track of the transitions parsed to create the matrix when
+    // done
+    vector<Transition> transitions;
+
+    // open input file
+    ifstream infile;
+    infile.open(file_name.c_str(), ifstream::in);
+    if (!infile.is_open()) {
+        fatal("Traffic generator %s config file not found at %s\n",
+              owner.name(), file_name);
+    }
+
+    // read line by line and determine the action based on the first
+    // keyword
+    string keyword;
+    string line;
+
+    while (getline(infile, line).good()) {
+        // see if this line is a comment line, and if so skip it
+        if (line.find('#') != 1) {
+            // create an input stream for the tokenization
+            istringstream is(line);
+
+            // determine the keyword
+            is >> keyword;
+
+            if (keyword == "STATE") {
+                // parse the behaviour of this state
+                uint32_t id;
+                Tick duration;
+                string mode;
+
+                is >> id >> duration >> mode;
+
+                if (mode == "TRACE") {
+                    string traceFile;
+                    Addr addrOffset;
+
+                    is >> traceFile >> addrOffset;
+
+                    states[id] = new TraceGen(port, master_id, duration,
+                                              traceFile, addrOffset);
+                    DPRINTF(TrafficGen, "State: %d TraceGen\n", id);
+                } else if (mode == "IDLE") {
+                    states[id] = new IdleGen(port, master_id, duration);
+                    DPRINTF(TrafficGen, "State: %d IdleGen\n", id);
+                } else if (mode == "LINEAR" || mode == "RANDOM") {
+                    uint32_t read_percent;
+                    Addr start_addr;
+                    Addr end_addr;
+                    Addr blocksize;
+                    Tick min_period;
+                    Tick max_period;
+                    Addr data_limit;
+
+                    is >> read_percent >> start_addr >> end_addr >>
+                        blocksize >> min_period >> max_period >> data_limit;
+
+                    DPRINTF(TrafficGen, "%s, addr %x to %x, size %d,"
+                            " period %d to %d, %d%% reads\n",
+                            mode, start_addr, end_addr, blocksize, min_period,
+                            max_period, read_percent);
+
+                    if (read_percent > 100)
+                        panic("%s cannot have more than 100% reads", name());
+
+                    if (mode == "LINEAR") {
+                        states[id] = new LinearGen(port, master_id,
+                                                   duration, start_addr,
+                                                   end_addr, blocksize,
+                                                   min_period, max_period,
+                                                   read_percent, data_limit);
+                        DPRINTF(TrafficGen, "State: %d LinearGen\n", id);
+                    } else if (mode == "RANDOM") {
+                        states[id] = new RandomGen(port, master_id,
+                                                   duration, start_addr,
+                                                   end_addr, blocksize,
+                                                   min_period, max_period,
+                                                   read_percent, data_limit);
+                        DPRINTF(TrafficGen, "State: %d RandomGen\n", id);
+                    }
+                } else {
+                    fatal("%s: Unknown traffic generator mode: %s",
+                          name(), mode);
+                }
+            } else if (keyword == "TRANSITION") {
+                Transition transition;
+
+                is >> transition.from >> transition.to >> transition.p;
+
+                transitions.push_back(transition);
+
+                DPRINTF(TrafficGen, "Transition: %d -> %d\n", transition.from,
+                        transition.to);
+            } else if (keyword == "INIT") {
+                // set the initial state as the active state
+                is >> currState;
+
+                DPRINTF(TrafficGen, "Initial state: %d\n", currState);
+            }
+        }
+    }
+
+    // resize and populate state transition matrix
+    transitionMatrix.resize(transitions.size());
+    for (size_t i = 0; i < transitions.size(); i++) {
+        transitionMatrix[i].resize(transitions.size());
+    }
+
+    for (vector<Transition>::iterator t = transitions.begin();
+         t != transitions.end(); ++t) {
+        transitionMatrix[t->from][t->to] = t->p;
+    }
+
+    // ensure the egress edges do not have a probability larger than
+    // one
+    for (size_t i = 0; i < transitions.size(); i++) {
+        double sum = 0;
+        for (size_t j = 0; j < transitions.size(); j++) {
+            sum += transitionMatrix[i][j];
+        }
+
+        // avoid comparing floating point numbers
+        if (abs(sum - 1.0) > 0.001)
+            fatal("%s has transition probability != 1 for state %d\n",
+                  name(), i);
+    }
+
+    // close input file
+    infile.close();
+}
+
+void
+TrafficGen::StateGraph::update()
+{
+    // if we have reached the time for the next state transition, then
+    // perform the transition
+    if (curTick() >= nextTransitionTick) {
+        transition();
+    } else {
+        // we are still in the current state and should execute it
+        states[currState]->execute();
+    }
+}
+
+void
+TrafficGen::StateGraph::transition()
+{
+    // exit the current state
+    states[currState]->exit();
+
+    // determine next state
+    double p = random_mt.gen_real1();
+    assert(currState < transitionMatrix.size());
+    double cumulative = transitionMatrix[currState][0];
+    size_t i = 1;
+    while (p < cumulative && i != transitionMatrix[currState].size()) {
+        cumulative += transitionMatrix[currState][i];
+        ++i;
+    }
+    enterState(i);
+}
+
+void
+TrafficGen::StateGraph::enterState(uint32_t newState)
+{
+    DPRINTF(TrafficGen, "Transition to state %d\n", newState);
+
+    currState = newState;
+    nextTransitionTick += states[currState]->duration;
+    states[currState]->enter();
+}
+
+TrafficGen::StateGraph::BaseGen::BaseGen(QueuedMasterPort& _port,
+                                         MasterID master_id,
+                                         Tick _duration)
+    : port(_port), masterID(master_id), duration(_duration)
+{
+}
+
+void
+TrafficGen::StateGraph::LinearGen::enter()
+{
+    // reset the address and the data counter
+    nextAddr = startAddr;
+    dataManipulated = 0;
+
+    // this test only needs to happen once, but cannot be performed
+    // before init() is called and the ports are connected
+    if (port.deviceBlockSize() && blocksize > port.deviceBlockSize())
+        fatal("TrafficGen %s block size (%d) is larger than port"
+              " block size (%d)\n", blocksize, port.deviceBlockSize());
+
+}
+
+void
+TrafficGen::StateGraph::LinearGen::execute()
+{
+    // choose if we generate a read or a write here
+    bool isRead = random_mt.random<uint8_t>(0, 100) < readPercent;
+
+    if (readPercent == 0)
+        assert(!isRead);
+
+    DPRINTF(TrafficGen, "LinearGen::execute: %c to addr %x, size %d\n",
+            isRead ? 'r' : 'w', nextAddr, blocksize);
+
+    // Create new request
+    Request::Flags flags;
+    Request *req = new Request(nextAddr, blocksize, flags, masterID);
+
+    PacketPtr pkt = new Packet(req, isRead ? MemCmd::ReadReq :
+                               MemCmd::WriteReq);
+
+    uint8_t* pkt_data = new uint8_t[req->getSize()];
+    pkt->dataDynamicArray(pkt_data);
+
+    if (!isRead) {
+        memset(pkt_data, 0xA, req->getSize());
+    }
+
+    port.schedTimingReq(pkt, curTick());
+
+    // increment the address
+    nextAddr += blocksize;
+
+    // Add the amount of data manipulated to the total
+    dataManipulated += blocksize;
+}
+
+Tick
+TrafficGen::StateGraph::LinearGen::nextExecuteTick()
+{
+    // If we have reached the end of the address space, reset the
+    // address to the start of the range
+    if (nextAddr + blocksize > endAddr) {
+        DPRINTF(TrafficGen, "Wrapping address to the start of "
+                "the range\n");
+        nextAddr = startAddr;
+    }
+
+    // Check to see if we have reached the data limit. If dataLimit is
+    // zero we do not have a data limit and therefore we will keep
+    // generating requests for the entire residency in this state.
+    if (dataLimit && dataManipulated >= dataLimit) {
+        DPRINTF(TrafficGen, "Data limit for LinearGen reached.\n");
+        // there are no more requests, therefore return MaxTick
+        return MaxTick;
+    } else {
+        // return the time when the next request should take place
+        return curTick() + random_mt.random<Tick>(minPeriod, maxPeriod);
+    }
+}
+
+void
+TrafficGen::StateGraph::RandomGen::enter()
+{
+    // reset the counter to zero
+    dataManipulated = 0;
+
+    // this test only needs to happen once, but cannot be performed
+    // before init() is called and the ports are connected
+    if (port.deviceBlockSize() && blocksize > port.deviceBlockSize())
+        fatal("TrafficGen %s block size (%d) is larger than port"
+              " block size (%d)\n", name(), blocksize, port.deviceBlockSize());
+}
+
+void
+TrafficGen::StateGraph::RandomGen::execute()
+{
+    // choose if we generate a read or a write here
+    bool isRead = random_mt.random<uint8_t>(0, 100) < readPercent;
+
+    if (readPercent == 0)
+        assert(!isRead);
+
+    // address of the request
+    Addr addr = random_mt.random<Addr>(startAddr, endAddr - 1);
+
+    // round down to start address of block
+    addr -= addr % blocksize;
+
+    DPRINTF(TrafficGen, "RandomGen::execute: %c to addr %x, size %d\n",
+            isRead ? 'r' : 'w', addr, blocksize);
+
+    // create new request packet
+    Request::Flags flags;
+    Request *req = new Request(addr, blocksize, flags, masterID);
+
+    PacketPtr pkt = new Packet(req, isRead ? MemCmd::ReadReq :
+                               MemCmd::WriteReq);
+
+    uint8_t* pkt_data = new uint8_t[req->getSize()];
+    pkt->dataDynamicArray(pkt_data);
+
+    if (!isRead) {
+        memset(pkt_data, 0xA, req->getSize());
+    }
+
+    port.schedTimingReq(pkt, curTick());
+
+    // Add the amount of data manipulated to the total
+    dataManipulated += blocksize;
+}
+
+Tick
+TrafficGen::StateGraph::RandomGen::nextExecuteTick()
+{
+    // Check to see if we have reached the data limit. If dataLimit is
+    // zero we do not have a data limit and therefore we will keep
+    // generating requests for the entire residency in this state.
+    if (dataLimit && dataManipulated >= dataLimit)
+    {
+        DPRINTF(TrafficGen, "Data limit for RandomGen reached.\n");
+        // No more requests. Return MaxTick.
+        return MaxTick;
+    } else {
+        // Return the time when the next request should take place.
+        return curTick() + random_mt.random<Tick>(minPeriod, maxPeriod);
+    }
+}
+
+Tick
+TrafficGen::StateGraph::TraceGen::nextExecuteTick() {
+    // We need to look at the next line to calculate the next time an
+    // event occurs, or potentially return MaxTick to signal that
+    // nothing has to be done.
+    string buffer;
+    if (!traceComplete && trace.good()){
+        getline(trace, buffer);
+        DPRINTF(TrafficGen, "Input trace: %s\n", buffer);
+    } else {
+        // We are at the end of the file, thus we have no more data in
+        // the trace Return MaxTick to signal that there will be no
+        // more transactions in this active period for the state.
+        return MaxTick;
+    }
+
+    //Reset the nextElement to the default values
+    currElement = nextElement;
+    nextElement.clear();
+
+    // Check that we have something to process. This assume no EOF at
+    // the end of the line.
+    if (buffer.size() > 0 && !trace.eof()) {
+        istringstream iss(buffer);
+
+        char rOrW, ch;
+        iss >> rOrW;
+        iss >> ch; assert(ch == ',');
+        iss >> nextElement.addr;
+        iss >> ch; assert(ch == ',');
+        iss >> nextElement.blocksize;
+        iss >> ch; assert(ch == ',');
+        iss >> nextElement.tick;
+
+        if (rOrW == 'r') {
+            nextElement.cmd = MemCmd::ReadReq;
+        } else if (rOrW == 'w') {
+            nextElement.cmd = MemCmd::WriteReq;
+        } else {
+            fatal("Incorrect trace file format!\n");
+        }
+    }
+
+    // Check that we have a valid request
+    if (!nextElement.isValid()) {
+        // If it is not valid, assume that we have reached the end of
+        // the trace.  Even if this is not the case, we do not know
+        // what to do with the request as it makes no sense.
+        if (trace.good()) {
+            // Trace is good, therefore we are not at the end of the
+            // file. This means that the input trace cannot be read
+            // correctly or it contains data that makes no sense.
+            warn("Unable to read the trace file format\n");
+            warn("%s", buffer);
+        }
+
+        traceComplete = true;
+        return MaxTick;
+    }
+
+    DPRINTF(TrafficGen, "currElement: %c addr %d size %d tick %d (%d)\n",
+            currElement.cmd.isRead() ? 'r' : 'w',
+            currElement.addr,
+            currElement.blocksize,
+            currElement.tick + tickOffset,
+            currElement.tick);
+
+    DPRINTF(TrafficGen, "nextElement: %c addr %d size %d tick %d (%d)\n",
+            nextElement.cmd.isRead() ? 'r' : 'w',
+            nextElement.addr,
+            nextElement.blocksize,
+            nextElement.tick + tickOffset,
+            nextElement.tick);
+
+    return tickOffset + nextElement.tick;
+}
+
+void
+TrafficGen::StateGraph::TraceGen::enter() {
+    // update the trace offset to the time where the state was entered.
+    tickOffset = curTick();
+
+    // seek to the start of the input trace file
+    trace.seekg(0, ifstream::beg);
+    trace.clear();
+
+    // clear everything
+    nextElement.clear();
+    currElement.clear();
+
+    traceComplete = false;
+}
+
+void
+TrafficGen::StateGraph::TraceGen::execute() {
+    // it is the responsibility of nextExecuteTick to prevent the
+    // state graph from executing the state if it should not
+    assert(currElement.isValid());
+
+    DPRINTF(TrafficGen, "TraceGen::execute: %c %d %d %d\n",
+            currElement.cmd.isRead() ? 'r' : 'w',
+            currElement.addr,
+            currElement.blocksize,
+            currElement.tick);
+
+    Request::Flags flags;
+    Request *req = new Request(currElement.addr + addrOffset,
+                               currElement.blocksize, flags, masterID);
+
+    PacketPtr pkt = new Packet(req, currElement.cmd);
+
+    uint8_t* pkt_data = new uint8_t[req->getSize()];
+    pkt->dataDynamicArray(pkt_data);
+
+    if (currElement.cmd.isWrite()) {
+        memset(pkt_data, 0xA, req->getSize());
+    }
+
+    port.schedTimingReq(pkt, curTick());
+}
+
+void
+TrafficGen::StateGraph::TraceGen::exit() {
+    // Check if we reached the end of the trace file. If we did not
+    // then we want to generate a warning stating that not the entire
+    // trace was played.
+    if (!trace.eof()) {
+        warn("Trace player %s was unable to replay the entire trace!\n",
+             name());
+    }
+
+    // clear any previous error flags for the input trace file
+    trace.clear();
+}
+
+bool
+TrafficGen::TrafficGenPort::recvTimingResp(PacketPtr pkt)
+{
+    delete pkt->req;
+    delete pkt;
+
+    return true;
+}
diff --git a/src/cpu/testers/traffic_gen/traffic_gen.hh b/src/cpu/testers/traffic_gen/traffic_gen.hh
new file mode 100644
index 000000000..19182fa15
--- /dev/null
+++ b/src/cpu/testers/traffic_gen/traffic_gen.hh
@@ -0,0 +1,615 @@
+/*
+ * Copyright (c) 2012 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.
+ *
+ * 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: Thomas Grass
+ *          Andreas Hansson
+ *          Sascha Bischoff
+ */
+#ifndef __MEM_TRAFFIC_GEN_HH__
+#define __MEM_TRAFFIC_GEN_HH__
+
+#include <fstream>
+
+#include "base/hashmap.hh"
+#include "mem/mem_object.hh"
+#include "mem/qport.hh"
+#include "params/TrafficGen.hh"
+
+/**
+ * The traffic generator is a master module that generates stimuli for
+ * the memory system, based on a collection of simple behaviours that
+ * are either probabilistic or based on traces. It can be used stand
+ * alone for creating test cases for interconnect and memory
+ * controllers, or function as a black box replacement for system
+ * components that are not yet modelled in detail, e.g. a video engine
+ * or baseband subsystem.
+ */
+class TrafficGen : public MemObject
+{
+
+  private:
+
+    /**
+     * The system used to determine which mode we are currently operating
+     * in.
+     */
+    System* system;
+
+    /**
+     * MasterID used in generated requests.
+     */
+    MasterID masterID;
+
+  protected:
+
+    /**
+     * The state graph is responsible for instantiating and keeping
+     * track of the various generator states and also perform the
+     * transitions and call the appropriate functions when entering,
+     * executing and exiting a state.
+     */
+    class StateGraph
+    {
+
+      public:
+
+        /**
+         * Create a state graph from an input file.
+         *
+         * @param _owner used solely for the name
+         * @param _port port used to send requests
+         * @param file_name configuration description to read in
+         * @param master_id the unique id used for all requests
+         */
+        StateGraph(TrafficGen& _owner, QueuedMasterPort& _port,
+                   const std::string& file_name, MasterID master_id)
+            : nextTransitionTick(0), owner(_owner), port(_port)
+        {
+            parseConfig(file_name, master_id);
+        }
+
+        /**
+         * Get the name, used for DPRINTFs.
+         *
+         * @return the owner's name
+         */
+        std::string name() const { return owner.name(); }
+
+        /**
+         * Either perform a state transition or execute the current
+         * state, depending on the current time.
+         */
+        void update();
+
+        /**
+         * Determine next state and perform the transition.
+         */
+        void transition();
+
+        /**
+         * Enter a new state.
+         *
+         * @param newState identifier of state to enter
+         */
+        void enterState(uint32_t newState);
+
+        /**
+         * Get the tick of the next event, either an execution or a
+         * transition.
+         *
+         * @return tick of the next state graph event
+         */
+        Tick nextEventTick()
+        {
+            return std::min(states[currState]->nextExecuteTick(),
+                            nextTransitionTick);
+
+        }
+
+        /** Time of next transition */
+        Tick nextTransitionTick;
+
+      private:
+
+        /**
+         * Parse the config file and build the state map and
+         * transition matrix.
+         *
+         * @param file_name Config file name to parse
+         * @param master_id MasterID to use for generated requests
+         */
+        void parseConfig(const std::string& file_name, MasterID master_id);
+
+        /** Struct to represent a probabilistic transition during parsing. */
+        struct Transition {
+            uint32_t from;
+            uint32_t to;
+            double p;
+        };
+
+        /** Base class for all generator states */
+        class BaseGen
+        {
+
+          protected:
+
+            /** Port used to send requests */
+            QueuedMasterPort& port;
+
+            /** The MasterID used for generating requests */
+            const MasterID masterID;
+
+          public:
+
+            /** Time to spend in this state */
+            const Tick duration;
+
+            /**
+             * Create a base generator.
+             *
+             * @param _port port used to send requests
+             * @param master_id MasterID set on each request
+             * @param _duration duration of this state before transitioning
+             */
+            BaseGen(QueuedMasterPort& _port, MasterID master_id,
+                    Tick _duration);
+
+            virtual ~BaseGen() { }
+
+            /**
+             * Get the name, useful for DPRINTFs.
+             *
+             * @return the port name
+             */
+            std::string name() const { return port.name(); }
+
+            /**
+             * Enter this generator state.
+             */
+            virtual void enter() = 0;
+
+            /**
+             * Execute this generator state.
+             */
+            virtual void execute() = 0;
+
+            /**
+             * Exit this generator state. By default do nothing.
+             */
+            virtual void exit() { };
+
+            /**
+             * Determine the next execute tick. MaxTick means that
+             * there will not be any further event in the current
+             * activation cycle of the state.
+             *
+             * @return next tick when the state should be executed
+             */
+            virtual Tick nextExecuteTick() = 0;
+
+        };
+
+        /**
+         * The idle generator does nothing.
+         */
+        class IdleGen : public BaseGen
+        {
+
+          public:
+
+            IdleGen(QueuedMasterPort& _port, MasterID master_id,
+                    Tick _duration)
+                : BaseGen(_port, master_id, _duration)
+            { }
+
+            void enter() { }
+
+            void execute() { }
+
+            Tick nextExecuteTick() { return MaxTick; }
+        };
+
+        /**
+         * The linear generator generates sequential requests from a
+         * start to an end address, with a fixed block size. A
+         * fraction of the requests are reads, as determined by the
+         * read percent. There is an optional data limit for when to
+         * stop generating new requests.
+         */
+        class LinearGen : public BaseGen
+        {
+
+          public:
+
+            /**
+             * Create a linear address sequence generator. Set
+             * min_period == max_period for a fixed inter-transaction
+             * time.
+             *
+             * @param _port port used to send requests
+             * @param master_id MasterID set on each request
+             * @param _duration duration of this state before transitioning
+             * @param start_addr Start address
+             * @param end_addr End address
+             * @param _blocksize Size used for transactions injected
+             * @param min_period Lower limit of random inter-transaction time
+             * @param max_period Upper limit of random inter-transaction time
+             * @param read_percent Percent of transactions that are reads
+             * @param data_limit Upper limit on how much data to read/write
+             */
+            LinearGen(QueuedMasterPort& _port, MasterID master_id,
+                      Tick _duration, Addr start_addr, Addr end_addr,
+                      Addr _blocksize, Tick min_period, Tick max_period,
+                      uint8_t read_percent, Addr data_limit)
+                : BaseGen(_port, master_id, _duration),
+                  startAddr(start_addr), endAddr(end_addr),
+                  blocksize(_blocksize), minPeriod(min_period),
+                  maxPeriod(max_period), readPercent(read_percent),
+                  dataLimit(data_limit)
+            { }
+
+            void enter();
+
+            void execute();
+
+            Tick nextExecuteTick();
+
+          private:
+
+            /** Start of address range */
+            const Addr startAddr;
+
+            /** End of address range */
+            const Addr endAddr;
+
+            /** Blocksize and address increment */
+            const Addr blocksize;
+
+            /** Request generation period */
+            const Tick minPeriod;
+            const Tick maxPeriod;
+
+            /**
+             * Percent of generated transactions that should be reads
+             */
+            const uint8_t readPercent;
+
+            /** Maximum amount of data to manipulate */
+            const Addr dataLimit;
+
+            /** Address of next request */
+            Addr nextAddr;
+
+            /**
+             * Counter to determine the amount of data
+             * manipulated. Used to determine if we should continue
+             * generating requests.
+             */
+            Addr dataManipulated;
+        };
+
+        /**
+         * The random generator is similar to the linear one, but does
+         * not generate sequential addresses. Instead it randomly
+         * picks an address in the range, aligned to the block size.
+         */
+        class RandomGen : public BaseGen
+        {
+
+          public:
+
+            /**
+             * Create a random address sequence generator. Set
+             * min_period == max_period for a fixed inter-transaction
+             * time.
+             *
+             * @param _port port used to send requests
+             * @param master_id MasterID set on each request
+             * @param _duration duration of this state before transitioning
+             * @param start_addr Start address
+             * @param end_addr End address
+             * @param _blocksize Size used for transactions injected
+             * @param min_period Lower limit of random inter-transaction time
+             * @param max_period Upper limit of random inter-transaction time
+             * @param read_percent Percent of transactions that are reads
+             * @param data_limit Upper limit on how much data to read/write
+             */
+            RandomGen(QueuedMasterPort& _port, MasterID master_id,
+                      Tick _duration, Addr start_addr, Addr end_addr,
+                      Addr _blocksize, Tick min_period, Tick max_period,
+                      uint8_t read_percent, Addr data_limit)
+                : BaseGen(_port, master_id, _duration),
+                  startAddr(start_addr), endAddr(end_addr),
+                  blocksize(_blocksize), minPeriod(min_period),
+                  maxPeriod(max_period), readPercent(read_percent),
+                  dataLimit(data_limit)
+            { }
+
+            void enter();
+
+            void execute();
+
+            Tick nextExecuteTick();
+
+          private:
+
+            /** Start of address range */
+            const Addr startAddr;
+
+            /** End of address range */
+            const Addr endAddr;
+
+            /** Block size */
+            const Addr blocksize;
+
+            /** Request generation period */
+            const Tick minPeriod;
+            const Tick maxPeriod;
+
+            /**
+             * Percent of generated transactions that should be reads
+             */
+            const uint8_t readPercent;
+
+            /** Maximum amount of data to manipulate */
+            const Addr dataLimit;
+
+            /**
+             * Counter to determine the amount of data
+             * manipulated. Used to determine if we should continue
+             * generating requests.
+             */
+            Addr dataManipulated;
+        };
+
+        /**
+         * The trace replay generator reads a trace file and plays
+         * back the transactions. The trace is offset with respect to
+         * the time when the state was entered.
+         */
+        class TraceGen : public BaseGen
+        {
+
+          private:
+
+            /**
+             * This struct stores a line in the trace file.
+             */
+            struct TraceElement {
+
+                /** Specifies if the request is to be a read or a write */
+                MemCmd cmd;
+
+                /** The address for the request */
+                Addr addr;
+
+                /** The size of the access for the request */
+                Addr blocksize;
+
+                /** The time at which the request should be sent */
+                Tick tick;
+
+                /**
+                 * Check validity of this element.
+                 *
+                 * @return if this element is valid
+                 */
+                bool isValid() const {
+                    return cmd != MemCmd::InvalidCmd;
+                }
+
+                /**
+                 * Make this element invalid.
+                 */
+                void clear() {
+                    cmd = MemCmd::InvalidCmd;
+                }
+            };
+
+          public:
+
+           /**
+             * Create a trace generator.
+             *
+             * @param _port port used to send requests
+             * @param master_id MasterID set on each request
+             * @param _duration duration of this state before transitioning
+             * @param trace_file File to read the transactions from
+             * @param addr_offset Positive offset to add to trace address
+             */
+            TraceGen(QueuedMasterPort& _port, MasterID master_id,
+                     Tick _duration, const std::string& trace_file,
+                     Addr addr_offset)
+                : BaseGen(_port, master_id, _duration),
+                  traceFile(trace_file),
+                  addrOffset(addr_offset),
+                  traceComplete(false)
+            {
+                /**
+                 * Create a 4MB read buffer for the input trace
+                 * file. This is to reduce the number of disk accesses
+                 * and thereby speed up the execution of the code.
+                 */
+                readBuffer = new char[4 * 1024 * 1024];
+                trace.rdbuf()->pubsetbuf(readBuffer, 4 * 1024 * 1024);
+                trace.open(traceFile.c_str(), std::ifstream::in);
+
+                if (!trace.is_open()) {
+                    fatal("Traffic generator %s trace file could not be"
+                          " opened: %s\n", name(), traceFile);
+                }
+            }
+
+            ~TraceGen() {
+                // free the memory used by the readBuffer
+                delete[] readBuffer;
+            }
+
+            void enter();
+
+            void execute();
+
+            void exit();
+
+            /**
+             * Read a line of the trace file. Returns the raw tick
+             * when the next request should be generated. If the end
+             * of the file has been reached, it returns MaxTick to
+             * indicate that there will be no more requests.
+             */
+            Tick nextExecuteTick();
+
+          private:
+
+            /** Path to the trace file */
+            std::string traceFile;
+
+            /** Input stream used for reading the input trace file */
+            std::ifstream trace;
+
+            /** Larger buffer used for reading from the stream */
+            char* readBuffer;
+
+            /** Store the current and next element in the trace */
+            TraceElement currElement;
+            TraceElement nextElement;
+
+            /**
+             * Stores the time when the state was entered. This is to add an
+             * offset to the times stored in the trace file.
+             */
+            Tick tickOffset;
+
+            /**
+             * Offset for memory requests. Used to shift the trace
+             * away from the CPU address space.
+             */
+            Addr addrOffset;
+
+            /**
+             * Set to true when the trace replay for one instance of
+             * state is complete.
+             */
+            bool traceComplete;
+
+            /**
+             * Used to store the Tick when the next generate should
+             * occur. It is to remove a transaction as soon as we
+             * enter the state.
+             */
+            Tick oldEmitTime;
+        };
+
+        /** Pointer to owner of request handler */
+        TrafficGen& owner;
+
+        /** Pointer to request handler */
+        QueuedMasterPort& port;
+
+        /** State transition matrix */
+        std::vector<std::vector<double> > transitionMatrix;
+
+      public:
+
+        /** Index of the current state */
+        uint32_t currState;
+
+        /** Map of states */
+        m5::hash_map<uint32_t, BaseGen*> states;
+    };
+
+
+    /** Queued handler */
+    class TrafficGenPort : public QueuedMasterPort
+    {
+      public:
+
+        TrafficGenPort(const std::string& name, TrafficGen& _owner)
+            : QueuedMasterPort(name, &_owner, queue), queue(_owner, *this),
+              owner(_owner)
+        { }
+
+      protected:
+
+        bool recvTimingResp(PacketPtr pkt);
+
+      private:
+
+        MasterPacketQueue queue;
+
+        // Owner of the port
+        TrafficGen& owner;
+
+    };
+
+    TrafficGenPort port;
+
+    /** Request generator state graph */
+    StateGraph stateGraph;
+
+    /**
+     * Schedules event for next update and executes an update on the
+     * state graph.
+     */
+    void updateStateGraph();
+
+    /** Event for updating the state graph */
+    EventWrapper<TrafficGen,
+                 &TrafficGen::updateStateGraph> updateStateGraphEvent;
+
+
+  public:
+
+    TrafficGen(const TrafficGenParams* p);
+
+    ~TrafficGen() {}
+
+    virtual MasterPort& getMasterPort(const std::string &if_name,
+                                      int idx = InvalidPortID);
+
+    void init();
+
+    void initState();
+
+    unsigned int drain(Event *drain_event);
+
+    void serialize(std::ostream &os);
+
+    void unserialize(Checkpoint* cp, const std::string& section);
+
+};
+
+#endif //__MEM_TRAFFIC_GEN_HH__