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 random replacement policy.
34 * The victim is chosen at random, if there are no invalid entries.
35 */
36
37#ifndef __MEM_CACHE_REPLACEMENT_POLICIES_RANDOM_RP_HH__
38#define __MEM_CACHE_REPLACEMENT_POLICIES_RANDOM_RP_HH__
39
40#include "mem/cache/replacement_policies/base.hh"
41
42struct RandomRPParams;
43
44class RandomRP : public BaseReplacementPolicy
45{
46  protected:
47    /** MRU-specific implementation of replacement data. */
48    struct RandomReplData : ReplacementData
49    {
50        /**
51         * Flag informing if the replacement data is valid or not.
52         * Invalid entries are prioritized to be evicted.
53         */
54        bool valid;
55
56        /**
57         * Default constructor. Invalidate data.
58         */
59        RandomReplData() : valid(false) {}
60    };
61
62  public:
63    /** Convenience typedef. */
64    typedef RandomRPParams Params;
65
66    /**
67     * Construct and initiliaze this replacement policy.
68     */
69    RandomRP(const Params *p);
70
71    /**
72     * Destructor.
73     */
74    ~RandomRP() {}
75
76    /**
77     * Invalidate replacement data to set it as the next probable victim.
78     * Prioritize replacement data for victimization.
79     *
80     * @param replacement_data Replacement data to be invalidated.
81     */
82    void invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
83                                                               const override;
84
85    /**
86     * Touch an entry to update its replacement data.
87     * Does not do anything.
88     *
89     * @param replacement_data Replacement data to be touched.
90     */
91    void touch(const std::shared_ptr<ReplacementData>& replacement_data) const
92                                                                     override;
93
94    /**
95     * Reset replacement data. Used when an entry is inserted.
96     * Unprioritize replacement data for victimization.
97     *
98     * @param replacement_data Replacement data to be reset.
99     */
100    void reset(const std::shared_ptr<ReplacementData>& replacement_data) const
101                                                                     override;
102
103    /**
104     * Find replacement victim at random.
105     *
106     * @param candidates Replacement candidates, selected by indexing policy.
107     * @return Replacement entry to be replaced.
108     */
109    ReplaceableEntry* getVictim(const ReplacementCandidates& candidates) const
110                                                                     override;
111
112    /**
113     * Instantiate a replacement data entry.
114     *
115     * @return A shared pointer to the new replacement data.
116     */
117    std::shared_ptr<ReplacementData> instantiateEntry() override;
118};
119
120#endif // __MEM_CACHE_REPLACEMENT_POLICIES_RANDOM_RP_HH__
121