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author | Daniel R. Carvalho <odanrc@yahoo.com.br> | 2018-03-23 16:08:51 +0100 |
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committer | Daniel Carvalho <odanrc@yahoo.com.br> | 2018-05-03 14:26:58 +0000 |
commit | 04d236e5687ba11d71ced0a37044fdd55aa5bb42 (patch) | |
tree | 2db8621bd8889b0ac06875f2fe6c6228676df720 /src/mem/cache/replacement_policies/second_chance_rp.cc | |
parent | c149983d931054d8cf88d2977a1f03a0b8b3b543 (diff) | |
download | gem5-04d236e5687ba11d71ced0a37044fdd55aa5bb42.tar.xz |
mem-cache: Create Second-Chance replacement policy
Implementation of a Second-Chance replacement policy. Similar to FIFO,
but every block is given a second chance if it has been touched.
Change-Id: Id4d52b698d0045a4914a4d848fdf9c3c00a28508
Reviewed-on: https://gem5-review.googlesource.com/9441
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Diffstat (limited to 'src/mem/cache/replacement_policies/second_chance_rp.cc')
-rw-r--r-- | src/mem/cache/replacement_policies/second_chance_rp.cc | 134 |
1 files changed, 134 insertions, 0 deletions
diff --git a/src/mem/cache/replacement_policies/second_chance_rp.cc b/src/mem/cache/replacement_policies/second_chance_rp.cc new file mode 100644 index 000000000..2560a9846 --- /dev/null +++ b/src/mem/cache/replacement_policies/second_chance_rp.cc @@ -0,0 +1,134 @@ +/** + * Copyright (c) 2018 Inria + * All rights reserved. + * + * 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. + * + * Authors: Daniel Carvalho + */ + +#include "mem/cache/replacement_policies/second_chance_rp.hh" + +SecondChanceRP::SecondChanceRP(const Params *p) + : FIFORP(p) +{ +} + +void +SecondChanceRP::useSecondChance( + const std::shared_ptr<SecondChanceReplData>& replacement_data) const +{ + // Reset FIFO data + FIFORP::reset(replacement_data); + + // Use second chance + replacement_data->hasSecondChance = false; +} + +void +SecondChanceRP::invalidate( + const std::shared_ptr<ReplacementData>& replacement_data) const +{ + FIFORP::invalidate(replacement_data); + + // Do not give a second chance to invalid entries + std::static_pointer_cast<SecondChanceReplData>( + replacement_data)->hasSecondChance = false; +} + +void +SecondChanceRP::touch(const std::shared_ptr<ReplacementData>& replacement_data) const +{ + FIFORP::touch(replacement_data); + + // Whenever an entry is touched, it is given a second chance + std::static_pointer_cast<SecondChanceReplData>( + replacement_data)->hasSecondChance = true; +} + +void +SecondChanceRP::reset(const std::shared_ptr<ReplacementData>& replacement_data) const +{ + FIFORP::reset(replacement_data); + + // Entries are inserted with a second chance + std::static_pointer_cast<SecondChanceReplData>( + replacement_data)->hasSecondChance = true; +} + +ReplaceableEntry* +SecondChanceRP::getVictim(const ReplacementCandidates& candidates) const +{ + // There must be at least one replacement candidate + assert(candidates.size() > 0); + + // Search for invalid entries, as they have the eviction priority + for (const auto& candidate : candidates) { + // Cast candidate's replacement data + std::shared_ptr<SecondChanceReplData> candidate_replacement_data = + std::static_pointer_cast<SecondChanceReplData>( + candidate->replacementData); + + // Stop iteration if found an invalid entry + if ((candidate_replacement_data->tickInserted == Tick(0)) && + !candidate_replacement_data->hasSecondChance) { + return candidate; + } + } + + // Visit all candidates to find victim + ReplaceableEntry* victim = candidates[0]; + bool search_victim = true; + while (search_victim) { + // Do a FIFO victim search + victim = FIFORP::getVictim(candidates); + + // Cast victim's replacement data for code readability + std::shared_ptr<SecondChanceReplData> victim_replacement_data = + std::static_pointer_cast<SecondChanceReplData>( + victim->replacementData); + + // If victim has a second chance, use it and repeat search + if (victim_replacement_data->hasSecondChance) { + useSecondChance(victim_replacement_data); + } else { + // Found victim + search_victim = false; + } + } + + return victim; +} + +std::shared_ptr<ReplacementData> +SecondChanceRP::instantiateEntry() +{ + return std::shared_ptr<ReplacementData>(new SecondChanceReplData()); +} + +SecondChanceRP* +SecondChanceRPParams::create() +{ + return new SecondChanceRP(this); +} |