brrip_rp.cc revision 14211:acfef4916339
1/** 2 * Copyright (c) 2018 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 * Authors: Daniel Carvalho 29 */ 30 31#include "mem/cache/replacement_policies/brrip_rp.hh" 32 33#include <cassert> 34#include <memory> 35 36#include "base/logging.hh" // For fatal_if 37#include "base/random.hh" 38#include "params/BRRIPRP.hh" 39 40BRRIPRP::BRRIPRP(const Params *p) 41 : BaseReplacementPolicy(p), 42 numRRPVBits(p->num_bits), hitPriority(p->hit_priority), btp(p->btp) 43{ 44 fatal_if(numRRPVBits <= 0, "There should be at least one bit per RRPV.\n"); 45} 46 47void 48BRRIPRP::invalidate(const std::shared_ptr<ReplacementData>& replacement_data) 49const 50{ 51 std::shared_ptr<BRRIPReplData> casted_replacement_data = 52 std::static_pointer_cast<BRRIPReplData>(replacement_data); 53 54 // Invalidate entry 55 casted_replacement_data->valid = false; 56} 57 58void 59BRRIPRP::touch(const std::shared_ptr<ReplacementData>& replacement_data) const 60{ 61 std::shared_ptr<BRRIPReplData> casted_replacement_data = 62 std::static_pointer_cast<BRRIPReplData>(replacement_data); 63 64 // Update RRPV if not 0 yet 65 // Every hit in HP mode makes the entry the last to be evicted, while 66 // in FP mode a hit makes the entry less likely to be evicted 67 if (hitPriority) { 68 casted_replacement_data->rrpv.reset(); 69 } else { 70 casted_replacement_data->rrpv--; 71 } 72} 73 74void 75BRRIPRP::reset(const std::shared_ptr<ReplacementData>& replacement_data) const 76{ 77 std::shared_ptr<BRRIPReplData> casted_replacement_data = 78 std::static_pointer_cast<BRRIPReplData>(replacement_data); 79 80 // Reset RRPV 81 // Replacement data is inserted as "long re-reference" if lower than btp, 82 // "distant re-reference" otherwise 83 casted_replacement_data->rrpv.saturate(); 84 if (random_mt.random<unsigned>(1, 100) <= btp) { 85 casted_replacement_data->rrpv--; 86 } 87 88 // Mark entry as ready to be used 89 casted_replacement_data->valid = true; 90} 91 92ReplaceableEntry* 93BRRIPRP::getVictim(const ReplacementCandidates& candidates) const 94{ 95 // There must be at least one replacement candidate 96 assert(candidates.size() > 0); 97 98 // Use first candidate as dummy victim 99 ReplaceableEntry* victim = candidates[0]; 100 101 // Store victim->rrpv in a variable to improve code readability 102 int victim_RRPV = std::static_pointer_cast<BRRIPReplData>( 103 victim->replacementData)->rrpv; 104 105 // Visit all candidates to find victim 106 for (const auto& candidate : candidates) { 107 std::shared_ptr<BRRIPReplData> candidate_repl_data = 108 std::static_pointer_cast<BRRIPReplData>( 109 candidate->replacementData); 110 111 // Stop searching for victims if an invalid entry is found 112 if (!candidate_repl_data->valid) { 113 return candidate; 114 } 115 116 // Update victim entry if necessary 117 int candidate_RRPV = candidate_repl_data->rrpv; 118 if (candidate_RRPV > victim_RRPV) { 119 victim = candidate; 120 victim_RRPV = candidate_RRPV; 121 } 122 } 123 124 // Get difference of victim's RRPV to the highest possible RRPV in 125 // order to update the RRPV of all the other entries accordingly 126 int diff = std::static_pointer_cast<BRRIPReplData>( 127 victim->replacementData)->rrpv.saturate(); 128 129 // No need to update RRPV if there is no difference 130 if (diff > 0){ 131 // Update RRPV of all candidates 132 for (const auto& candidate : candidates) { 133 std::static_pointer_cast<BRRIPReplData>( 134 candidate->replacementData)->rrpv += diff; 135 } 136 } 137 138 return victim; 139} 140 141std::shared_ptr<ReplacementData> 142BRRIPRP::instantiateEntry() 143{ 144 return std::shared_ptr<ReplacementData>(new BRRIPReplData(numRRPVBits)); 145} 146 147BRRIPRP* 148BRRIPRPParams::create() 149{ 150 return new BRRIPRP(this); 151} 152