src/mem/cache/replacement_policies/mru_rp.cc

   1 /**
   2  * Copyright (c) 2018-2020 Inria
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include "mem/cache/replacement_policies/mru_rp.hh"
  30
  31 #include <cassert>
  32 #include <memory>
  33
  34 #include "params/MRURP.hh"
  35 #include "sim/core.hh"
  36
  37 namespace ReplacementPolicy {
  38
  39 MRU::MRU(const Params &p)
  40   : Base(p)
  41 {
  42 }
  43
  44 void
  45 MRU::invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
  46 const
  47 {
  48     // Reset last touch timestamp
  49     std::static_pointer_cast<MRUReplData>(
  50         replacement_data)->lastTouchTick = Tick(0);
  51 }
  52
  53 void
  54 MRU::touch(const std::shared_ptr<ReplacementData>& replacement_data) const
  55 {
  56     // Update last touch timestamp
  57     std::static_pointer_cast<MRUReplData>(
  58         replacement_data)->lastTouchTick = curTick();
  59 }
  60
  61 void
  62 MRU::reset(const std::shared_ptr<ReplacementData>& replacement_data) const
  63 {
  64     // Set last touch timestamp
  65     std::static_pointer_cast<MRUReplData>(
  66         replacement_data)->lastTouchTick = curTick();
  67 }
  68
  69 ReplaceableEntry*
  70 MRU::getVictim(const ReplacementCandidates& candidates) const
  71 {
  72     // There must be at least one replacement candidate
  73     assert(candidates.size() > 0);
  74
  75     // Visit all candidates to find victim
  76     ReplaceableEntry* victim = candidates[0];
  77     for (const auto& candidate : candidates) {
  78         std::shared_ptr<MRUReplData> candidate_replacement_data =
  79             std::static_pointer_cast<MRUReplData>(candidate->replacementData);
  80
  81         // Stop searching entry if a cache line that doesn't warm up is found.
  82         if (candidate_replacement_data->lastTouchTick == 0) {
  83             victim = candidate;
  84             break;
  85         } else if (candidate_replacement_data->lastTouchTick >
  86                 std::static_pointer_cast<MRUReplData>(
  87                     victim->replacementData)->lastTouchTick) {
  88             victim = candidate;
  89         }
  90     }
  91
  92     return victim;
  93 }
  94
  95 std::shared_ptr<ReplacementData>
  96 MRU::instantiateEntry()
  97 {
  98     return std::shared_ptr<ReplacementData>(new MRUReplData());
  99 }
 100
 101 } // namespace ReplacementPolicy
 102
 103 ReplacementPolicy::MRU*
 104 MRURPParams::create() const
 105 {
 106     return new ReplacementPolicy::MRU(*this);
 107 }