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 Most Recently Used replacement policy.
34 * The victim is chosen using the timestamp. The entry that was accessed the
35 * last is the one chosen to be replaced.
36 */
37
38#ifndef __MEM_CACHE_REPLACEMENT_POLICIES_MRU_RP_HH__
39#define __MEM_CACHE_REPLACEMENT_POLICIES_MRU_RP_HH__
40
41#include "base/types.hh"
42#include "mem/cache/replacement_policies/base.hh"
42#include "params/MRURP.hh"
43
44struct MRURPParams;
45
46class MRURP : public BaseReplacementPolicy
47{
48 protected:
49 /** MRU-specific implementation of replacement data. */
50 struct MRUReplData : ReplacementData
51 {
52 /** Tick on which the entry was last touched. */
53 Tick lastTouchTick;
54
55 /**
56 * Default constructor. Invalidate data.
57 */
58 MRUReplData() : lastTouchTick(0) {}
59 };
60
61 public:
62 /** Convenience typedef. */
63 typedef MRURPParams Params;
64
65 /**
66 * Construct and initiliaze this replacement policy.
67 */
68 MRURP(const Params *p);
69
70 /**
71 * Destructor.
72 */
73 ~MRURP() {}
74
75 /**
76 * Invalidate replacement data to set it as the next probable victim.
77 * Sets its last touch tick as the starting tick.
78 *
79 * @param replacement_data Replacement data to be invalidated.
80 */
81 void invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
82 const override;
83
84 /**
85 * Touch an entry to update its replacement data.
86 * Sets its last touch tick as the current tick.
87 *
88 * @param replacement_data Replacement data to be touched.
89 */
90 void touch(const std::shared_ptr<ReplacementData>& replacement_data) const
91 override;
92
93 /**
94 * Reset replacement data. Used when an entry is inserted.
95 * Sets its last touch tick as the current tick.
96 *
97 * @param replacement_data Replacement data to be reset.
98 */
99 void reset(const std::shared_ptr<ReplacementData>& replacement_data) const
100 override;
101
102 /**
103 * Find replacement victim using access timestamps.
104 *
105 * @param cands Replacement candidates, selected by indexing policy.
106 * @return Replacement entry to be replaced.
107 */
108 ReplaceableEntry* getVictim(const ReplacementCandidates& candidates) const
109 override;
110
111 /**
112 * Instantiate a replacement data entry.
113 *
114 * @return A shared pointer to the new replacement data.
115 */
116 std::shared_ptr<ReplacementData> instantiateEntry() override;
117};
118
119#endif // __MEM_CACHE_REPLACEMENT_POLICIES_MRU_RP_HH__