src/mem/qos/turnaround_policy_ideal.cc

   1 /*
   2  * Copyright (c) 2018 ARM Limited
   3  * All rights reserved
   4  *
   5  * The license below extends only to copyright in the software and shall
   6  * not be construed as granting a license to any other intellectual
   7  * property including but not limited to intellectual property relating
   8  * to a hardware implementation of the functionality of the software
   9  * licensed hereunder.  You may use the software subject to the license
  10  * terms below provided that you ensure that this notice is replicated
  11  * unmodified and in its entirety in all distributions of the software,
  12  * modified or unmodified, in source code or in binary form.
  13  *
  14  * Redistribution and use in source and binary forms, with or without
  15  * modification, are permitted provided that the following conditions are
  16  * met: redistributions of source code must retain the above copyright
  17  * notice, this list of conditions and the following disclaimer;
  18  * redistributions in binary form must reproduce the above copyright
  19  * notice, this list of conditions and the following disclaimer in the
  20  * documentation and/or other materials provided with the distribution;
  21  * neither the name of the copyright holders nor the names of its
  22  * contributors may be used to endorse or promote products derived from
  23  * this software without specific prior written permission.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  26  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  27  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  28  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  29  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  30  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  31  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  35  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "turnaround_policy_ideal.hh"
  39
  40 #include "params/QoSTurnaroundPolicyIdeal.hh"
  41
  42 namespace QoS {
  43
  44 TurnaroundPolicyIdeal::TurnaroundPolicyIdeal(const Params &p)
  45   : TurnaroundPolicy(p)
  46 {}
  47
  48 TurnaroundPolicyIdeal::~TurnaroundPolicyIdeal()
  49 {}
  50
  51 MemCtrl::BusState
  52 TurnaroundPolicyIdeal::selectBusState()
  53 {
  54     auto bus_state = memCtrl->getBusState();
  55     const auto num_priorities = memCtrl->numPriorities();
  56
  57     // QoS-aware turnaround policy
  58     // Loop for every queue in the memory controller.
  59     for (uint8_t i = 0; i < num_priorities; i++) {
  60
  61         // Starting from top priority queues first
  62         uint8_t queue_idx = num_priorities - i - 1;
  63
  64         const uint64_t readq_size = memCtrl->getReadQueueSize(queue_idx);
  65         const uint64_t writeq_size = memCtrl->getWriteQueueSize(queue_idx);
  66
  67         // No data for current priority: both the read queue
  68         // and write queue are empty.
  69         if ((readq_size == 0) && (writeq_size == 0)) {
  70             continue;
  71         }
  72
  73         // Data found - select state
  74         if (readq_size == 0) {
  75             bus_state = MemCtrl::WRITE;
  76         } else if (writeq_size == 0) {
  77             bus_state = MemCtrl::READ;
  78         } else {
  79             // readq_size > 0 && writeq_size > 0
  80             bus_state = ((memCtrl->getBusState() == MemCtrl::READ) ?
  81                     MemCtrl::WRITE : MemCtrl::READ);
  82         }
  83
  84         DPRINTF(QOS,
  85                 "QoSMemoryTurnaround::QoSTurnaroundPolicyIdeal - "
  86                 "QoS priority %d queues %d, %d triggering bus %s "
  87                 "in state %s\n", queue_idx, readq_size, writeq_size,
  88                 (bus_state != memCtrl->getBusState()) ?
  89                 "turnaround" : "staying",
  90                 (bus_state == MemCtrl::READ)? "READ" : "WRITE");
  91         // State selected - exit loop
  92         break;
  93     }
  94
  95     return bus_state;
  96 }
  97
  98 } // namespace QoS