src/mem/cache/replacement_policies/weighted_lru_rp.cc

   1 /*
   2  * Copyright (c) 2013-2015 Advanced Micro Devices, Inc.
   3  * All rights reserved.
   4  *
   5  * For use for simulation and test purposes only
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright notice,
  11  * this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright notice,
  14  * this list of conditions and the following disclaimer in the documentation
  15  * and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the copyright holder nor the names of its
  18  * contributors may be used to endorse or promote products derived from this
  19  * software without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  22  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  25  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  26  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  27  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  28  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  29  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  30  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31  * POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 #include "mem/cache/replacement_policies/weighted_lru_rp.hh"
  35
  36 #include <cassert>
  37
  38 #include "params/WeightedLRURP.hh"
  39 #include "sim/core.hh"
  40
  41 WeightedLRUPolicy::WeightedLRUPolicy(const Params* p)
  42     : BaseReplacementPolicy(p)
  43 {
  44 }
  45
  46 WeightedLRUPolicy *
  47 WeightedLRURPParams::create()
  48 {
  49     return new WeightedLRUPolicy(this);
  50 }
  51
  52 void
  53 WeightedLRUPolicy::touch(const std::shared_ptr<ReplacementData>&
  54                                                   replacement_data) const
  55 {
  56     std::static_pointer_cast<WeightedLRUReplData>(replacement_data)->
  57                                                  last_touch_tick = curTick();
  58 }
  59
  60 void
  61 WeightedLRUPolicy::touch(const std::shared_ptr<ReplacementData>&
  62                         replacement_data, int occupancy) const
  63 {
  64     std::static_pointer_cast<WeightedLRUReplData>(replacement_data)->
  65                                                   last_touch_tick = curTick();
  66     std::static_pointer_cast<WeightedLRUReplData>(replacement_data)->
  67                                                   last_occ_ptr = occupancy;
  68 }
  69
  70 ReplaceableEntry*
  71 WeightedLRUPolicy::getVictim(const ReplacementCandidates& candidates) const
  72 {
  73     assert(candidates.size() > 0);
  74
  75     ReplaceableEntry* victim = candidates[0];
  76     // Use weight (last_occ_ptr) to find victim.
  77     // Evict the block that has the smallest weight.
  78     // If two blocks have the same weight, evict the oldest one.
  79     for (const auto& candidate : candidates) {
  80         // candidate's replacement_data
  81         std::shared_ptr<WeightedLRUReplData> candidate_replacement_data =
  82             std::static_pointer_cast<WeightedLRUReplData>(
  83                                              candidate->replacementData);
  84         // victim's replacement_data
  85         std::shared_ptr<WeightedLRUReplData> victim_replacement_data =
  86             std::static_pointer_cast<WeightedLRUReplData>(
  87                                              victim->replacementData);
  88
  89         if (candidate_replacement_data->last_occ_ptr <
  90                     victim_replacement_data->last_occ_ptr) {
  91             victim = candidate;
  92         } else if (candidate_replacement_data->last_occ_ptr ==
  93                     victim_replacement_data->last_occ_ptr) {
  94             // Evict the block with a smaller tick.
  95             Tick time = candidate_replacement_data->last_touch_tick;
  96             if (time < victim_replacement_data->last_touch_tick) {
  97                 victim = candidate;
  98             }
  99         }
 100     }
 101     return victim;
 102 }
 103
 104 std::shared_ptr<ReplacementData>
 105 WeightedLRUPolicy::instantiateEntry()
 106 {
 107     return std::shared_ptr<ReplacementData>(new WeightedLRUReplData);
 108 }
 109
 110 void
 111 WeightedLRUPolicy::reset(const std::shared_ptr<ReplacementData>&
 112                                                     replacement_data) const
 113 {
 114     // Set last touch timestamp
 115     std::static_pointer_cast<WeightedLRUReplData>(
 116         replacement_data)->last_touch_tick = curTick();
 117 }
 118
 119 void
 120 WeightedLRUPolicy::invalidate(const std::shared_ptr<ReplacementData>&
 121                                                     replacement_data) const
 122 {
 123     // Reset last touch timestamp
 124     std::static_pointer_cast<WeightedLRUReplData>(
 125         replacement_data)->last_touch_tick = Tick(0);
 126 }