| /** |
| * 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. |
| */ |
| |
| /** |
| * @file |
| * Declaration of a Re-Reference Interval Prediction replacement policy. |
| * |
| * Not-Recently Used (NRU) is an approximation of LRU that uses a single bit |
| * to determine if an entry is going to be re-referenced in the near or distant |
| * future. |
| * |
| * Re-Reference Interval Prediction (RRIP) is an extension of NRU that uses a |
| * re-reference prediction value to determine if entries are going to be re- |
| * used in the near future or not. |
| * |
| * The higher the value of the RRPV, the more distant the entry is from its |
| * next access. |
| * |
| * Bimodal Re-Reference Interval Prediction (BRRIP) is an extension of RRIP |
| * that has a probability of not inserting entries as the LRU. This probability |
| * is controlled by the bimodal throtle parameter (btp). |
| * |
| * From the original paper, this implementation of RRIP is also called |
| * Static RRIP (SRRIP), as it always inserts entries with the same RRPV. |
| */ |
| |
| #ifndef __MEM_CACHE_REPLACEMENT_POLICIES_BRRIP_RP_HH__ |
| #define __MEM_CACHE_REPLACEMENT_POLICIES_BRRIP_RP_HH__ |
| |
| #include "base/sat_counter.hh" |
| #include "mem/cache/replacement_policies/base.hh" |
| |
| struct BRRIPRPParams; |
| |
| class BRRIPRP : public BaseReplacementPolicy |
| { |
| protected: |
| /** BRRIP-specific implementation of replacement data. */ |
| struct BRRIPReplData : ReplacementData |
| { |
| /** |
| * Re-Reference Interval Prediction Value. |
| * Some values have specific names (according to the paper): |
| * 0 -> near-immediate re-rereference interval |
| * max_RRPV-1 -> long re-rereference interval |
| * max_RRPV -> distant re-rereference interval |
| */ |
| SatCounter rrpv; |
| |
| /** Whether the entry is valid. */ |
| bool valid; |
| |
| /** |
| * Default constructor. Invalidate data. |
| */ |
| BRRIPReplData(const int num_bits) |
| : rrpv(num_bits), valid(false) |
| { |
| } |
| }; |
| |
| /** |
| * Number of RRPV bits. An entry that saturates its RRPV has the longest |
| * possible re-reference interval, that is, it is likely not to be used |
| * in the near future, and is among the best eviction candidates. |
| * A maximum RRPV of 1 implies in a NRU. |
| */ |
| const unsigned numRRPVBits; |
| |
| /** |
| * The hit priority (HP) policy replaces entries that do not receive cache |
| * hits over any cache entry that receives a hit, while the frequency |
| * priority (FP) policy replaces infrequently re-referenced entries. |
| */ |
| const bool hitPriority; |
| |
| /** |
| * Bimodal throtle parameter. Value in the range [0,100] used to decide |
| * if a new entry is inserted with long or distant re-reference. |
| */ |
| const unsigned btp; |
| |
| public: |
| /** Convenience typedef. */ |
| typedef BRRIPRPParams Params; |
| |
| /** |
| * Construct and initiliaze this replacement policy. |
| */ |
| BRRIPRP(const Params *p); |
| |
| /** |
| * Destructor. |
| */ |
| ~BRRIPRP() {} |
| |
| /** |
| * Invalidate replacement data to set it as the next probable victim. |
| * Set RRPV as the the most distant re-reference. |
| * |
| * @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. |
| * |
| * @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. |
| * Set RRPV according to the insertion policy used. |
| * |
| * @param replacement_data Replacement data to be reset. |
| */ |
| void reset(const std::shared_ptr<ReplacementData>& replacement_data) const |
| override; |
| |
| /** |
| * Find replacement victim using rrpv. |
| * |
| * @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_BRRIP_RP_HH__ |