mem: Add a QoS-aware Memory Controller type

This is the implementation of QoS algorithms support for gem5 memory
objects. This change-list provides a framework for specifying QoS
algorithm which can be used to prioritise service to specific masters in
the memory controller.
The QoS support implemented here is designed to be extendable so that
new QoS algorithms can be easily plugged into the memory controller as
"QoS Policies".

Change-Id: I0b611f13fce54dd1dd444eb806f8e98afd248bd5
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/11970
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

1 files changed, 355 insertions, 0 deletions

diff --git a/src/mem/qos/mem_ctrl.cc b/src/mem/qos/mem_ctrl.cc
new file mode 100644
index 000000000..ce15fd779
--- /dev/null
+++ b/src/mem/qos/mem_ctrl.cc
@@ -0,0 +1,355 @@
+/*
+ * Copyright (c) 2017 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: Matteo Andreozzi
+ */
+
+#include "mem_ctrl.hh"
+
+#include "turnaround_policy.hh"
+
+namespace QoS {
+
+MemCtrl::MemCtrl(const QoSMemCtrlParams * p)
+  : AbstractMemory(p),
+    policy(p->qos_policy),
+    turnPolicy(p->qos_turnaround_policy),
+    queuePolicy(QueuePolicy::create(p)),
+    _numPriorities(p->qos_priorities),
+    qosPriorityEscalation(p->qos_priority_escalation),
+    qosSyncroScheduler(p->qos_syncro_scheduler),
+    totalReadQueueSize(0), totalWriteQueueSize(0),
+    busState(READ), busStateNext(READ)
+{
+    // Set the priority policy
+    if (policy) {
+        policy->setMemCtrl(this);
+    }
+
+    // Set the queue priority policy
+    if (queuePolicy) {
+        queuePolicy->setMemCtrl(this);
+    }
+
+    // Set the bus turnaround policy
+    if (turnPolicy) {
+        turnPolicy->setMemCtrl(this);
+    }
+
+    readQueueSizes.resize(_numPriorities);
+    writeQueueSizes.resize(_numPriorities);
+    serviceTick.resize(_numPriorities);
+}
+
+MemCtrl::~MemCtrl()
+{}
+
+void
+MemCtrl::init()
+{
+    AbstractMemory::init();
+}
+
+void
+MemCtrl::logRequest(BusState dir, MasterID m_id, uint8_t qos,
+                    Addr addr, uint64_t entries)
+{
+    // If needed, initialize all counters and statistics
+    // for this master
+    addMaster(m_id);
+
+    DPRINTF(QOS,
+            "QoSMemCtrl::logRequest MASTER %s [id %d] address %d"
+            " prio %d this master q packets %d"
+            " - queue size %d - requested entries %d\n",
+            masters[m_id], m_id, addr, qos, packetPriorities[m_id][qos],
+            (dir == READ) ? readQueueSizes[qos]: writeQueueSizes[qos],
+            entries);
+
+    if (dir == READ) {
+        readQueueSizes[qos] += entries;
+        totalReadQueueSize += entries;
+    } else if (dir == WRITE) {
+        writeQueueSizes[qos] += entries;
+        totalWriteQueueSize += entries;
+    }
+
+    packetPriorities[m_id][qos] += entries;
+    for (auto j = 0; j < entries; ++j) {
+        requestTimes[m_id][addr].push_back(curTick());
+    }
+
+    // Record statistics
+    avgPriority[m_id].sample(qos);
+
+    // Compute avg priority distance
+
+    for (uint8_t i = 0; i < packetPriorities[m_id].size(); ++i) {
+        uint8_t distance =
+            (abs(int(qos) - int(i))) * packetPriorities[m_id][i];
+
+        if (distance > 0) {
+            avgPriorityDistance[m_id].sample(distance);
+            DPRINTF(QOS,
+                    "QoSMemCtrl::logRequest MASTER %s [id %d]"
+                    " registering priority distance %d for priority %d"
+                    " (packets %d)\n",
+                    masters[m_id], m_id, distance, i,
+                    packetPriorities[m_id][i]);
+        }
+    }
+
+    DPRINTF(QOS,
+            "QoSMemCtrl::logRequest MASTER %s [id %d] prio %d "
+            "this master q packets %d - new queue size %d\n",
+            masters[m_id], m_id, qos, packetPriorities[m_id][qos],
+            (dir == READ) ? readQueueSizes[qos]: writeQueueSizes[qos]);
+
+}
+
+void
+MemCtrl::logResponse(BusState dir, MasterID m_id, uint8_t qos,
+                     Addr addr, uint64_t entries, double delay)
+{
+    panic_if(!hasMaster(m_id),
+        "Logging response with invalid master\n");
+
+    DPRINTF(QOS,
+            "QoSMemCtrl::logResponse MASTER %s [id %d] address %d prio"
+            " %d this master q packets %d"
+            " - queue size %d - requested entries %d\n",
+            masters[m_id], m_id, addr, qos, packetPriorities[m_id][qos],
+            (dir == READ) ? readQueueSizes[qos]: writeQueueSizes[qos],
+            entries);
+
+    if (dir == READ) {
+        readQueueSizes[qos] -= entries;
+        totalReadQueueSize -= entries;
+    } else if (dir == WRITE) {
+        writeQueueSizes[qos] -= entries;
+        totalWriteQueueSize -= entries;
+    }
+
+    panic_if(packetPriorities[m_id][qos] == 0,
+             "QoSMemCtrl::logResponse master %s negative packets for priority"
+             " %d", masters[m_id], qos);
+
+    packetPriorities[m_id][qos] -= entries;
+
+    for (auto j = 0; j < entries; ++j) {
+        auto it = requestTimes[m_id].find(addr);
+        panic_if(it == requestTimes[m_id].end(),
+                 "QoSMemCtrl::logResponse master %s unmatched response for"
+                 " address %d received", masters[m_id], addr);
+
+        // Load request time
+        uint64_t requestTime = it->second.front();
+
+        // Remove request entry
+        it->second.pop_front();
+
+        // Remove whole address entry if last one
+        if (it->second.empty()) {
+            requestTimes[m_id].erase(it);
+        }
+        // Compute latency
+        double latency = (double) (curTick() + delay - requestTime)
+                / SimClock::Float::s;
+
+        if (latency > 0) {
+            // Record per-priority latency stats
+            if (priorityMaxLatency[qos].value() < latency) {
+                priorityMaxLatency[qos] = latency;
+            }
+
+            if (priorityMinLatency[qos].value() > latency
+                    || priorityMinLatency[qos].value() == 0) {
+                priorityMinLatency[qos] = latency;
+            }
+        }
+    }
+
+    DPRINTF(QOS,
+            "QoSMemCtrl::logResponse MASTER %s [id %d] prio %d "
+            "this master q packets %d - new queue size %d\n",
+            masters[m_id], m_id, qos, packetPriorities[m_id][qos],
+            (dir == READ) ? readQueueSizes[qos]: writeQueueSizes[qos]);
+}
+
+uint8_t
+MemCtrl::schedule(MasterID m_id, uint64_t data)
+{
+    if (policy) {
+        return policy->schedule(m_id, data);
+    } else {
+        DPRINTF(QOS,
+                "QoSScheduler::schedule master ID [%d] "
+                "data received [%d], but QoS scheduler not initialized\n",
+                m_id,data);
+        return 0;
+    }
+}
+
+uint8_t
+MemCtrl::schedule(const PacketPtr pkt)
+{
+    assert(pkt->req);
+
+    if (policy) {
+        return schedule(pkt->req->masterId(), pkt->getSize());
+    } else {
+        DPRINTF(QOS, "QoSScheduler::schedule Packet received [Qv %d], "
+                "but QoS scheduler not initialized\n",
+                pkt->qosValue());
+        return pkt->qosValue();
+    }
+}
+
+MemCtrl::BusState
+MemCtrl::selectNextBusState()
+{
+    auto bus_state = getBusState();
+
+    if (turnPolicy) {
+        DPRINTF(QOS,
+                "QoSMemoryTurnaround::selectBusState running policy %s\n",
+                turnPolicy->name());
+
+        bus_state = turnPolicy->selectBusState();
+    } else {
+        DPRINTF(QOS,
+                "QoSMemoryTurnaround::selectBusState running "
+                "default bus direction selection policy\n");
+
+        if ((!getTotalReadQueueSize() && bus_state == MemCtrl::READ) ||
+            (!getTotalWriteQueueSize() && bus_state == MemCtrl::WRITE)) {
+            // READ/WRITE turnaround
+            bus_state = (bus_state == MemCtrl::READ) ? MemCtrl::WRITE :
+                                                       MemCtrl::READ;
+
+        }
+    }
+
+    return bus_state;
+}
+
+void
+MemCtrl::addMaster(MasterID m_id)
+{
+    if (!hasMaster(m_id)) {
+        masters.emplace(m_id, _system->getMasterName(m_id));
+        packetPriorities[m_id].resize(numPriorities(), 0);
+
+        DPRINTF(QOS,
+                "QoSMemCtrl::addMaster registering"
+                " Master %s [id %d]\n",
+                masters[m_id], m_id);
+    }
+}
+
+void
+MemCtrl::regStats()
+{
+    AbstractMemory::regStats();
+
+    using namespace Stats;
+
+    // Initializes per master statistics
+    avgPriority.init(_system->maxMasters()).name(name() + ".avgPriority")
+        .desc("Average QoS priority value for accepted requests")
+        .flags(nozero | nonan).precision(2);
+
+    avgPriorityDistance.init(_system->maxMasters())
+        .name(name() + ".avgPriorityDistance")
+        .desc("Average QoS priority distance between assigned and "
+        "queued values").flags(nozero | nonan);
+
+    priorityMinLatency.init(numPriorities())
+        .name(name() + ".priorityMinLatency")
+        .desc("per QoS priority minimum request to response latency (s)")
+        .precision(12);
+
+    priorityMaxLatency.init(numPriorities())
+        .name(name() + ".priorityMaxLatency")
+        .desc("per QoS priority maximum request to response latency (s)")
+        .precision(12);
+
+    numReadWriteTurnArounds.name(name() + ".numReadWriteTurnArounds")
+        .desc("Number of turnarounds from READ to WRITE");
+
+    numWriteReadTurnArounds.name(name() + ".numWriteReadTurnArounds")
+        .desc("Number of turnarounds from WRITE to READ");
+
+    numStayReadState.name(name() + ".numStayReadState")
+        .desc("Number of times bus staying in READ state");
+
+    numStayWriteState.name(name() + ".numStayWriteState")
+        .desc("Number of times bus staying in WRITE state");
+
+    for (int i = 0; i < _system->maxMasters(); i++) {
+        const std::string master = _system->getMasterName(i);
+        avgPriority.subname(i, master);
+        avgPriorityDistance.subname(i, master);
+    }
+
+    for (int j = 0; j < numPriorities(); ++j) {
+        priorityMinLatency.subname(j, std::to_string(j));
+        priorityMaxLatency.subname(j, std::to_string(j));
+    }
+
+    if (policy)
+        policy->regStats();
+}
+
+void
+MemCtrl::recordTurnaroundStats()
+{
+    if (busStateNext != busState) {
+        if (busState == READ) {
+            numWriteReadTurnArounds++;
+        } else if (busState == WRITE) {
+            numReadWriteTurnArounds++;
+        }
+    } else {
+        if (busState == READ) {
+            numStayReadState++;
+        } else if (busState == WRITE) {
+            numStayWriteState++;
+        }
+    }
+}
+
+} // namespace QoS