src/mem/cache/replacement_policies/mru_rp.cc

/**
 * Copyright (c) 2018-2020 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
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 * 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
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 */

#include "mem/cache/replacement_policies/mru_rp.hh"

#include <cassert>
#include <memory>

#include "params/MRURP.hh"
#include "sim/cur_tick.hh"

namespace gem5
{

GEM5_DEPRECATED_NAMESPACE(ReplacementPolicy, replacement_policy);
namespace replacement_policy
{

MRU::MRU(const Params &p)
  : Base(p)
{
}

void
MRU::invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
{
    // Reset last touch timestamp
    std::static_pointer_cast<MRUReplData>(
        replacement_data)->lastTouchTick = Tick(0);
}

void
MRU::touch(const std::shared_ptr<ReplacementData>& replacement_data) const
{
    // Update last touch timestamp
    std::static_pointer_cast<MRUReplData>(
        replacement_data)->lastTouchTick = curTick();
}

void
MRU::reset(const std::shared_ptr<ReplacementData>& replacement_data) const
{
    // Set last touch timestamp
    std::static_pointer_cast<MRUReplData>(
        replacement_data)->lastTouchTick = curTick();
}

ReplaceableEntry*
MRU::getVictim(const ReplacementCandidates& candidates) const
{
    // There must be at least one replacement candidate
    assert(candidates.size() > 0);

    // Visit all candidates to find victim
    ReplaceableEntry* victim = candidates[0];
    for (const auto& candidate : candidates) {
        std::shared_ptr<MRUReplData> candidate_replacement_data =
            std::static_pointer_cast<MRUReplData>(candidate->replacementData);

        // Stop searching entry if a cache line that doesn't warm up is found.
        if (candidate_replacement_data->lastTouchTick == 0) {
            victim = candidate;
            break;
        } else if (candidate_replacement_data->lastTouchTick >
                std::static_pointer_cast<MRUReplData>(
                    victim->replacementData)->lastTouchTick) {
            victim = candidate;
        }
    }

    return victim;
}

std::shared_ptr<ReplacementData>
MRU::instantiateEntry()
{
    return std::shared_ptr<ReplacementData>(new MRUReplData());
}

} // namespace replacement_policy
} // namespace gem5