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/**
* 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"
#include <cassert>
#include "params/SecondChanceRP.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);
}
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