src/mem/ruby/system/WeightedLRUPolicy.hh

/*
 * Copyright (c) 2013-2015 Advanced Micro Devices, Inc.
 * All rights reserved.
 *
 * For use for simulation and test purposes only
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. Neither the name of the copyright holder 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 HOLDER 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: Sooraj Puthoor
 */

#ifndef __MEM_RUBY_SYSTEM_WEIGHTEDLRUPOLICY_HH__
#define __MEM_RUBY_SYSTEM_WEIGHTEDLRUPOLICY_HH__

#include "mem/cache/replacement_policies/base.hh"
#include "mem/ruby/structures/CacheMemory.hh"
#include "params/WeightedLRUReplacementPolicy.hh"

/* Simple true LRU replacement policy */

class WeightedLRUPolicy : public BaseReplacementPolicy
{
  protected:
    /** Weighted LRU implementation of replacement data. */
    struct WeightedLRUReplData : ReplacementData
    {
        /** pointer for last occupancy */
        int last_occ_ptr;

        /** Tick on which the entry was last touched. */
        Tick last_touch_tick;

        /**
         * Default constructor. Invalidate data.
         */
        WeightedLRUReplData() : ReplacementData(),
                                last_occ_ptr(0), last_touch_tick(0) {}
    };
  public:
    typedef WeightedLRUReplacementPolicyParams Params;
    WeightedLRUPolicy(const Params* p);
    ~WeightedLRUPolicy() {}

    /**
     * Invalidate replacement data to set it as the next probable victim.
     * Sets its last touch tick as the starting tick.
     *
     * @param replacement_data Replacement data to be invalidated.
     */
    void invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
                                                              const override;
    /**
     * Touch an entry to update its replacement data.
     * Sets its last touch tick as the current tick.
     *
     * @param replacement_data Replacement data to be touched.
     */
    void touch(const std::shared_ptr<ReplacementData>&
                                        replacement_data) const override;
    void touch(const std::shared_ptr<ReplacementData>& replacement_data,
                                        int occupancy) const;

    /**
     * Reset replacement data. Used when an entry is inserted.
     * Sets its last touch tick as the current tick.
     *
     * @param replacement_data Replacement data to be reset.
     */
    void reset(const std::shared_ptr<ReplacementData>& replacement_data) const
                                                                     override;

    /**
     * Instantiate a replacement data entry.
     *
     * @return A shared pointer to the new replacement data.
     */
    std::shared_ptr<ReplacementData> instantiateEntry() override;

    /**
     * Find replacement victim using weight.
     *
     * @param candidates Replacement candidates, selected by indexing policy.
     * @return Replacement entry to be replaced.
     */
    ReplaceableEntry* getVictim(const ReplacementCandidates&
                                              candidates) const override;
};

#endif // __MEM_RUBY_SYSTEM_WeightedLRUPolicy_HH__