src/mem/cache/replacement_policies/ship_rp.cc

/**
 * Copyright (c) 2019, 2020 Inria
 * All rights reserved.
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 * met: redistributions of source code must retain the above copyright
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 * neither the name of the copyright holders nor the names of its
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 * 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/ship_rp.hh"

#include "base/logging.hh"
#include "params/SHiPMemRP.hh"
#include "params/SHiPPCRP.hh"
#include "params/SHiPRP.hh"

namespace gem5
{

namespace replacement_policy
{

SHiP::SHiPReplData::SHiPReplData(int num_bits)
  : BRRIPReplData(num_bits), signature(0), outcome(false)
{
}

SHiP::SignatureType
SHiP::SHiPReplData::getSignature() const
{
    return signature;
}

void
SHiP::SHiPReplData::setSignature(SignatureType new_signature)
{
    signature = new_signature;
    outcome = false;
}

void
SHiP::SHiPReplData::setReReferenced()
{
    outcome = true;
}

bool
SHiP::SHiPReplData::wasReReferenced() const
{
    return outcome;
}

SHiP::SHiP(const Params &p)
  : BRRIP(p), insertionThreshold(p.insertion_threshold / 100.0),
    SHCT(p.shct_size, SatCounter8(numRRPVBits))
{
}

void
SHiP::invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
{
    std::shared_ptr<SHiPReplData> casted_replacement_data =
        std::static_pointer_cast<SHiPReplData>(replacement_data);

    // The predictor is detrained when an entry that has not been re-
    // referenced since insertion is invalidated
    if (casted_replacement_data->wasReReferenced()) {
        SHCT[casted_replacement_data->getSignature()]--;
    }

    BRRIP::invalidate(replacement_data);
}

void
SHiP::touch(const std::shared_ptr<ReplacementData>& replacement_data,
    const PacketPtr pkt)
{
    std::shared_ptr<SHiPReplData> casted_replacement_data =
        std::static_pointer_cast<SHiPReplData>(replacement_data);

    // When a hit happens the SHCT entry indexed by the signature is
    // incremented
    SHCT[getSignature(pkt)]++;
    casted_replacement_data->setReReferenced();

    // This was a hit; update replacement data accordingly
    BRRIP::touch(replacement_data);
}

void
SHiP::touch(const std::shared_ptr<ReplacementData>& replacement_data)
    const
{
    panic("Cant train SHiP's predictor without access information.");
}

void
SHiP::reset(const std::shared_ptr<ReplacementData>& replacement_data,
    const PacketPtr pkt)
{
    std::shared_ptr<SHiPReplData> casted_replacement_data =
        std::static_pointer_cast<SHiPReplData>(replacement_data);

    // Get signature
    const SignatureType signature = getSignature(pkt);

    // Store signature
    casted_replacement_data->setSignature(signature);

    // If SHCT for signature is set, predict intermediate re-reference.
    // Predict distant re-reference otherwise
    BRRIP::reset(replacement_data);
    if (SHCT[signature].calcSaturation() >= insertionThreshold) {
        casted_replacement_data->rrpv--;
    }
}

void
SHiP::reset(const std::shared_ptr<ReplacementData>& replacement_data)
    const
{
    panic("Cant train SHiP's predictor without access information.");
}

std::shared_ptr<ReplacementData>
SHiP::instantiateEntry()
{
    return std::shared_ptr<ReplacementData>(new SHiPReplData(numRRPVBits));
}

SHiPMem::SHiPMem(const SHiPMemRPParams &p) : SHiP(p) {}

SHiP::SignatureType
SHiPMem::getSignature(const PacketPtr pkt) const
{
    return static_cast<SignatureType>(pkt->getAddr() % SHCT.size());
}

SHiPPC::SHiPPC(const SHiPPCRPParams &p) : SHiP(p) {}

SHiP::SignatureType
SHiPPC::getSignature(const PacketPtr pkt) const
{
    SignatureType signature;

    if (pkt->req->hasPC()) {
        signature = static_cast<SignatureType>(pkt->req->getPC());
    } else {
        signature = NO_PC_SIGNATURE;
    }

    return signature % SHCT.size();
}

} // namespace replacement_policy
} // namespace gem5