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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/brrip_rp.hh"
#include <memory>
#include "base/logging.hh" // For fatal_if
#include "base/random.hh"
BRRIPRP::BRRIPRP(const Params *p)
: BaseReplacementPolicy(p),
maxRRPV(p->max_RRPV), hitPriority(p->hit_priority), btp(p->btp)
{
fatal_if(maxRRPV <= 0, "max_RRPV should be greater than zero.\n");
}
void
BRRIPRP::invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
const
{
std::shared_ptr<BRRIPReplData> casted_replacement_data =
std::static_pointer_cast<BRRIPReplData>(replacement_data);
// Set RRPV to an invalid distance
casted_replacement_data->rrpv = maxRRPV + 1;
}
void
BRRIPRP::touch(const std::shared_ptr<ReplacementData>& replacement_data) const
{
std::shared_ptr<BRRIPReplData> casted_replacement_data =
std::static_pointer_cast<BRRIPReplData>(replacement_data);
// Update RRPV if not 0 yet
// Every hit in HP mode makes the entry the last to be evicted, while
// in FP mode a hit makes the entry less likely to be evicted
if (hitPriority) {
casted_replacement_data->rrpv = 0;
} else if (casted_replacement_data->rrpv > 0) {
casted_replacement_data->rrpv--;
}
}
void
BRRIPRP::reset(const std::shared_ptr<ReplacementData>& replacement_data) const
{
std::shared_ptr<BRRIPReplData> casted_replacement_data =
std::static_pointer_cast<BRRIPReplData>(replacement_data);
// Reset RRPV
// Replacement data is inserted as "long re-reference" if lower than btp,
// "distant re-reference" otherwise
if (random_mt.random<unsigned>(1, 100) <= btp) {
casted_replacement_data->rrpv = maxRRPV-1;
} else {
casted_replacement_data->rrpv = maxRRPV;
}
}
ReplaceableEntry*
BRRIPRP::getVictim(const ReplacementCandidates& candidates) const
{
// There must be at least one replacement candidate
assert(candidates.size() > 0);
// Use first candidate as dummy victim
ReplaceableEntry* victim = candidates[0];
// Store victim->rrpv in a variable to improve code readability
int victim_RRPV = std::static_pointer_cast<BRRIPReplData>(
victim->replacementData)->rrpv;
// Visit all candidates to find victim
for (const auto& candidate : candidates) {
// Get candidate's rrpv
int candidate_RRPV = std::static_pointer_cast<BRRIPReplData>(
candidate->replacementData)->rrpv;
// Stop searching for victims if an invalid entry is found
if (candidate_RRPV == maxRRPV + 1) {
return candidate;
// Update victim entry if necessary
} else if (candidate_RRPV > victim_RRPV) {
victim = candidate;
victim_RRPV = candidate_RRPV;
}
}
// Get difference of victim's RRPV to the highest possible RRPV in
// order to update the RRPV of all the other entries accordingly
int diff = maxRRPV - victim_RRPV;
// No need to update RRPV if there is no difference
if (diff > 0){
// Update RRPV of all candidates
for (const auto& candidate : candidates) {
std::static_pointer_cast<BRRIPReplData>(
candidate->replacementData)->rrpv += diff;
}
}
return victim;
}
std::shared_ptr<ReplacementData>
BRRIPRP::instantiateEntry()
{
return std::shared_ptr<ReplacementData>(new BRRIPReplData(maxRRPV));
}
BRRIPRP*
BRRIPRPParams::create()
{
return new BRRIPRP(this);
}
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