src/mem/cache/replacement_policies/bip_rp.hh

/**
 * Copyright (c) 2018-2020 Inria
 * All rights reserved.
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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
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/**
 * @file
 * Declaration of a Bimodal Interval Prediction replacement policy.
 * Has a probability of when placing new entries, placing them as MRU.
 *
 * Although both LRU and LIP can be seen as specific cases of BIP
 * where the bimodal throtle parameter are 1 and 0, respectively, we
 * decide not to inherit from it, and do the other way around (inherit
 * from LRU) for efficiency reasons.
 *
 * In the original paper they use btp = 1/32 ~= 3%.
 */

#ifndef __MEM_CACHE_REPLACEMENT_POLICIES_BIP_RP_HH__
#define __MEM_CACHE_REPLACEMENT_POLICIES_BIP_RP_HH__

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

namespace gem5
{

struct BIPRPParams;

GEM5_DEPRECATED_NAMESPACE(ReplacementPolicy, replacement_policy);
namespace replacement_policy
{

class BIP : public LRU
{
  protected:
    /**
     * Bimodal throtle parameter. Value in the range [0,100] used to decide
     * if a new entry is inserted at the MRU or LRU position.
     */
    const unsigned btp;

  public:
    typedef BIPRPParams Params;
    BIP(const Params &p);
    ~BIP() = default;

    /**
     * Reset replacement data for an entry. Used when an entry is inserted.
     * Uses the bimodal throtle parameter to decide whether the new entry
     * should be inserted as MRU, or LRU.
     *
     * @param replacement_data Replacement data to be reset.
     */
    void reset(const std::shared_ptr<ReplacementData>& replacement_data) const
                                                                     override;
};

} // namespace replacement_policy
} // namespace gem5

#endif // __MEM_CACHE_REPLACEMENT_POLICIES_BIP_RP_HH__