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Diffstat (limited to 'src/mem/cache/replacement_policies/second_chance_rp.hh')
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diff --git a/src/mem/cache/replacement_policies/second_chance_rp.hh b/src/mem/cache/replacement_policies/second_chance_rp.hh new file mode 100644 index 000000000..5522d5e7f --- /dev/null +++ b/src/mem/cache/replacement_policies/second_chance_rp.hh @@ -0,0 +1,133 @@ +/** + * 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 + */ + +/** + * @file + * Declaration of a Second-Chance replacement policy. + * The victim is chosen using the timestamp. The oldest entry is chosen + * to be evicted, if it hasn't been touched since its insertion. If it + * has been touched, it is given a second chance and re-inserted at the + * end of the queue. + */ + +#ifndef __MEM_CACHE_REPLACEMENT_POLICIES_SECOND_CHANCE_RP_HH__ +#define __MEM_CACHE_REPLACEMENT_POLICIES_SECOND_CHANCE_RP_HH__ + +#include "mem/cache/replacement_policies/fifo_rp.hh" +#include "params/SecondChanceRP.hh" + +class SecondChanceRP : public FIFORP +{ + protected: + /** Second-Chance-specific implementation of replacement data. */ + struct SecondChanceReplData : public FIFOReplData + { + /** + * This is different from isTouched because isTouched accounts only + * for insertion, while this bit is reset every new re-insertion. + * @sa SecondChanceRP. + */ + bool hasSecondChance; + + /** + * Default constructor. + */ + SecondChanceReplData() : FIFOReplData(), hasSecondChance(false) {} + }; + + /** + * Use replacement data's second chance. + * + * @param replacement_data Entry that will use its second chance. + */ + void useSecondChance( + const std::shared_ptr<SecondChanceReplData>& replacement_data) const; + + public: + /** Convenience typedef. */ + typedef SecondChanceRPParams Params; + + /** + * Construct and initiliaze this replacement policy. + */ + SecondChanceRP(const Params *p); + + /** + * Destructor. + */ + ~SecondChanceRP() {} + + /** + * Invalidate replacement data to set it as the next probable victim. + * Invalid entries do not have a second chance, and their last touch tick + * is set as the oldest possible. + * + * @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 re-insertion tick and second chance bit. + * + * @param replacement_data Replacement data to be touched. + */ + void touch(const std::shared_ptr<ReplacementData>& replacement_data) const + override; + + /** + * Reset replacement data. Used when an entry is inserted or re-inserted + * in the queue. + * Sets its insertion tick and second chance bit. + * + * @param replacement_data Replacement data to be reset. + */ + void reset(const std::shared_ptr<ReplacementData>& replacement_data) const + override; + + /** + * Find replacement victim using insertion timestamps and second chance + * bit. + * + * @param cands Replacement candidates, selected by indexing policy. + * @return Replacement entry to be replaced. + */ + ReplaceableEntry* getVictim(const ReplacementCandidates& candidates) const + override; + + /** + * Instantiate a replacement data entry. + * + * @return A shared pointer to the new replacement data. + */ + std::shared_ptr<ReplacementData> instantiateEntry() override; +}; + +#endif // __MEM_CACHE_REPLACEMENT_POLICIES_SECOND_CHANCE_RP_HH__ |