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, 188 insertions, 0 deletions

diff --git a/src/mem/qos/q_policy.hh b/src/mem/qos/q_policy.hh
new file mode 100644
index 000000000..3e455e89c
--- /dev/null
+++ b/src/mem/qos/q_policy.hh
@@ -0,0 +1,188 @@
+/*
+ * Copyright (c) 2018 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.
+ *
+ * Author: Matteo Andreozzi
+ */
+
+#ifndef __MEM_QOS_Q_POLICY_HH__
+#define __MEM_QOS_Q_POLICY_HH__
+
+#include <deque>
+#include <unordered_set>
+
+#include "mem/packet.hh"
+#include "params/QoSMemCtrl.hh"
+
+namespace QoS {
+
+class MemCtrl;
+
+/**
+ * QoS Queue Policy
+ *
+ * The QoS Queue Policy class implements algorithms to schedule packets
+ * within the same QoS priority queue
+ */
+class QueuePolicy
+{
+  public:
+    typedef std::deque<PacketPtr> PacketQueue;
+
+    /**
+     * This factory method is used for generating the queue policy. It takes
+     * the memory controller params as an argument and returns the related
+     * QueuePolicy object.  If no particular QueuePolicy has been specified in
+     * the QoSMemCtrlParams, the method will default to a LIFO queue policy.
+     *
+     * @param p QoS::MemCtrl parameter variable
+     * @return Pointer to the QueuePolicy
+     */
+    static QueuePolicy* create(const QoSMemCtrlParams* p);
+
+    /**
+     * This method is called by the memory controller after it enqueues a
+     * packet. It is a way for the queue policy to hook into the packet
+     * enqueuing and update relevant metadata. This will then be used once
+     * the QueuePolicy::selectPacket will be called.
+     *
+     * @param pkt Enqueued packet
+     */
+    virtual void enqueuePacket(PacketPtr pkt) {};
+
+    /**
+     * Policy selector.
+     * The implementation of this virtual method selects the packet
+     * to be serviced from the packet queue passed as an argument.
+     *
+     * @param queue Packet queue
+     * @return Iterator pointing to the packet in the queue to be
+     *         serviced
+     */
+    virtual PacketQueue::iterator selectPacket(PacketQueue* queue) = 0;
+
+    /**
+     * Setting a pointer to the Memory Controller implementing
+     * the policy.
+     */
+    void setMemCtrl(MemCtrl* mem) { memCtrl = mem; };
+
+  protected:
+    QueuePolicy(const QoSMemCtrlParams* p)
+      : memCtrl(nullptr)
+    {}
+
+    /** Pointer to parent memory controller implementing the policy */
+    MemCtrl* memCtrl;
+};
+
+/** Last In First Out Queue Policy */
+class LifoQueuePolicy : public QueuePolicy
+{
+  public:
+    LifoQueuePolicy(const QoSMemCtrlParams* p)
+      : QueuePolicy(p)
+    {}
+
+    /**
+     * Implements LIFO packet select policy
+     *
+     * @param queue The queue in which to select a packet
+     * @return Iterator to the selected packet
+     */
+    PacketQueue::iterator
+    selectPacket(PacketQueue* queue) override
+    {
+        return queue->end();
+    }
+};
+
+/** First In First Out Queue Policy */
+class FifoQueuePolicy : public QueuePolicy
+{
+  public:
+    FifoQueuePolicy(const QoSMemCtrlParams* p)
+      : QueuePolicy(p)
+    {}
+
+    /**
+     * Implements FCFS packet select policy
+     *
+     * @param queue The queue in which to select a packet
+     * @return Iterator to the selected packet
+     */
+    PacketQueue::iterator
+    selectPacket(PacketQueue* queue) override
+    {
+        return queue->begin();
+    }
+};
+
+/**
+ * Least Recently Granted Queue Policy
+ * It selects packets from the queue with a round
+ * robin-like policy: using the master id as a switching
+ * parameter rather than switching over a time quantum.
+ */
+class LrgQueuePolicy : public QueuePolicy
+{
+  public:
+    LrgQueuePolicy(const QoSMemCtrlParams* p)
+      : QueuePolicy(p)
+    {}
+
+    void enqueuePacket(PacketPtr pkt) override;
+
+    /**
+     * Implements LRG packet select policy
+     *
+     * @param queue The queue in which to select a packet
+     * @return Iterator to the selected packet
+     */
+    PacketQueue::iterator
+    selectPacket(PacketQueue* queue) override;
+
+  protected:
+    /**
+     * Support structure for lrg algorithms:
+     * keeps track of serviced masters,
+     * always serve the front element.
+     */
+    std::list<MasterID> toServe;
+};
+
+} // namespace QoS
+
+#endif /* __MEM_QOS_Q_POLICY_HH__ */