brrip_rp.cc revision 12684:44ebd2bc020f 
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#include "mem/cache/replacement_policies/brrip_rp.hh"
32
33#include <memory>
34
35#include "base/logging.hh" // For fatal_if
36#include "base/random.hh"
37
38BRRIPRP::BRRIPRP(const Params *p)
39    : BaseReplacementPolicy(p),
40      maxRRPV(p->max_RRPV), hitPriority(p->hit_priority), btp(p->btp)
41{
42    fatal_if(maxRRPV <= 0, "max_RRPV should be greater than zero.\n");
43}
44
45void
46BRRIPRP::invalidate(const std::shared_ptr<ReplacementData>& replacement_data)
47const
48{
49    std::shared_ptr<BRRIPReplData> casted_replacement_data =
50        std::static_pointer_cast<BRRIPReplData>(replacement_data);
51
52    // Set RRPV to an invalid distance
53    casted_replacement_data->rrpv = maxRRPV + 1;
54}
55
56void
57BRRIPRP::touch(const std::shared_ptr<ReplacementData>& replacement_data) const
58{
59    std::shared_ptr<BRRIPReplData> casted_replacement_data =
60        std::static_pointer_cast<BRRIPReplData>(replacement_data);
61
62    // Update RRPV if not 0 yet
63    // Every hit in HP mode makes the entry the last to be evicted, while
64    // in FP mode a hit makes the entry less likely to be evicted
65    if (hitPriority) {
66        casted_replacement_data->rrpv = 0;
67    } else if (casted_replacement_data->rrpv > 0) {
68        casted_replacement_data->rrpv--;
69    }
70}
71
72void
73BRRIPRP::reset(const std::shared_ptr<ReplacementData>& replacement_data) const
74{
75    std::shared_ptr<BRRIPReplData> casted_replacement_data =
76        std::static_pointer_cast<BRRIPReplData>(replacement_data);
77
78    // Reset RRPV
79    // Replacement data is inserted as "long re-reference" if lower than btp,
80    // "distant re-reference" otherwise
81    if (random_mt.random<unsigned>(1, 100) <= btp) {
82        casted_replacement_data->rrpv = maxRRPV-1;
83    } else {
84        casted_replacement_data->rrpv = maxRRPV;
85    }
86}
87
88ReplaceableEntry*
89BRRIPRP::getVictim(const ReplacementCandidates& candidates) const
90{
91    // There must be at least one replacement candidate
92    assert(candidates.size() > 0);
93
94    // Use first candidate as dummy victim
95    ReplaceableEntry* victim = candidates[0];
96
97    // Store victim->rrpv in a variable to improve code readability
98    int victim_RRPV = std::static_pointer_cast<BRRIPReplData>(
99                        victim->replacementData)->rrpv;
100
101    // Visit all candidates to find victim
102    for (const auto& candidate : candidates) {
103        // Get candidate's rrpv
104        int candidate_RRPV = std::static_pointer_cast<BRRIPReplData>(
105                                    candidate->replacementData)->rrpv;
106
107        // Stop searching for victims if an invalid entry is found
108        if (candidate_RRPV == maxRRPV + 1) {
109            return candidate;
110        // Update victim entry if necessary
111        } else if (candidate_RRPV > victim_RRPV) {
112            victim = candidate;
113            victim_RRPV = candidate_RRPV;
114        }
115    }
116
117    // Get difference of victim's RRPV to the highest possible RRPV in
118    // order to update the RRPV of all the other entries accordingly
119    int diff = maxRRPV - victim_RRPV;
120
121    // No need to update RRPV if there is no difference
122    if (diff > 0){
123        // Update RRPV of all candidates
124        for (const auto& candidate : candidates) {
125            std::static_pointer_cast<BRRIPReplData>(
126                candidate->replacementData)->rrpv += diff;
127        }
128    }
129
130    return victim;
131}
132
133std::shared_ptr<ReplacementData>
134BRRIPRP::instantiateEntry()
135{
136    return std::shared_ptr<ReplacementData>(new BRRIPReplData(maxRRPV));
137}
138
139BRRIPRP*
140BRRIPRPParams::create()
141{
142    return new BRRIPRP(this);
143}
144