brrip_rp.hh revision 12626 
1/**
2 * Copyright (c) 2018 Inria
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Daniel Carvalho
29 */
30
31/**
32 * @file
33 * Declaration of a Re-Reference Interval Prediction replacement policy.
34 *
35 * Not-Recently Used (NRU) is an approximation of LRU that uses a single bit
36 * to determine if a block is going to be re-referenced in the near or distant
37 * future.
38 *
39 * Re-Reference Interval Prediction (RRIP) is an extension of NRU that uses a
40 * re-reference prediction value to determine if blocks are going to be re-
41 * used in the near future or not.
42 *
43 * The higher the value of the RRPV, the more distant the block is from
44 * its next access.
45 *
46 * Bimodal Re-Reference Interval Prediction (BRRIP) is an extension of RRIP
47 * that has a probability of not inserting blocks as the LRU. This probability
48 * is controlled by the bimodal throtle parameter (btp).
49 *
50 * From the original paper, this implementation of RRIP is also called
51 * Static RRIP (SRRIP), as it always inserts blocks with the same RRPV.
52 */
53
54#ifndef __MEM_CACHE_REPLACEMENT_POLICIES_BRRIP_RP_HH__
55#define __MEM_CACHE_REPLACEMENT_POLICIES_BRRIP_RP_HH__
56
57#include "mem/cache/replacement_policies/base.hh"
58#include "params/BRRIPRP.hh"
59
60class BRRIPRP : public BaseReplacementPolicy
61{
62  protected:
63    /**
64     * Maximum Re-Reference Prediction Value possible. A block with this
65     * value as the rrpv has the longest possible re-reference interval,
66     * that is, it is likely not to be used in the near future, and is
67     * among the best eviction candidates.
68     * A maxRRPV of 1 implies in a NRU.
69     */
70    const unsigned maxRRPV;
71
72    /**
73     * The hit priority (HP) policy replaces blocks that do not receive cache
74     * hits over any cache block that receives a hit, while the frequency
75     * priority (FP) policy replaces infrequently re-referenced blocks.
76     */
77    const bool hitPriority;
78
79    /**
80     * Bimodal throtle parameter. Value in the range [0,100] used to decide
81     * if a new block is inserted with long or distant re-reference.
82     */
83    const unsigned btp;
84
85  public:
86    /** Convenience typedef. */
87    typedef BRRIPRPParams Params;
88
89    /**
90     * Construct and initiliaze this replacement policy.
91     */
92    BRRIPRP(const Params *p);
93
94    /**
95     * Destructor.
96     */
97    ~BRRIPRP() {}
98
99    /**
100     * Touch a block to update its replacement data.
101     *
102     * @param blk Cache block to be touched.
103     */
104    void touch(CacheBlk *blk) override;
105
106    /**
107     * Reset replacement data for a block. Used when a block is inserted.
108     * Sets the insertion tick, and update correspondent replacement data.
109     * Set RRPV according to the insertion policy used.
110     *
111     * @param blk Cache block to be reset.
112     */
113    void reset(CacheBlk *blk) override;
114
115    /**
116     * Find replacement victim using rrpv.
117     *
118     * @param cands Replacement candidates, selected by indexing policy.
119     * @return Cache block to be replaced.
120     */
121    CacheBlk* getVictim(const ReplacementCandidates& candidates) override;
122};
123
124#endif // __MEM_CACHE_REPLACEMENT_POLICIES_BRRIP_RP_HH__
125