2 * Copyright (c) 2018 Inria
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6 * modification, are permitted provided that the following conditions are
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14 * this software without specific prior written permission.
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,
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26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 * Authors: Daniel Carvalho
31 #include "mem/cache/replacement_policies/brrip_rp.hh"
35 #include "base/logging.hh" // For fatal_if
36 #include "base/random.hh"
38 BRRIPRP::BRRIPRP(const Params
*p
)
39 : BaseReplacementPolicy(p
),
40 maxRRPV(p
->max_RRPV
), hitPriority(p
->hit_priority
), btp(p
->btp
)
42 fatal_if(maxRRPV
<= 0, "max_RRPV should be greater than zero.\n");
46 BRRIPRP::invalidate(const std::shared_ptr
<ReplacementData
>& replacement_data
)
49 std::shared_ptr
<BRRIPReplData
> casted_replacement_data
=
50 std::static_pointer_cast
<BRRIPReplData
>(replacement_data
);
52 // Set RRPV to an invalid distance
53 casted_replacement_data
->rrpv
= maxRRPV
+ 1;
57 BRRIPRP::touch(const std::shared_ptr
<ReplacementData
>& replacement_data
) const
59 std::shared_ptr
<BRRIPReplData
> casted_replacement_data
=
60 std::static_pointer_cast
<BRRIPReplData
>(replacement_data
);
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
66 casted_replacement_data
->rrpv
= 0;
67 } else if (casted_replacement_data
->rrpv
> 0) {
68 casted_replacement_data
->rrpv
--;
73 BRRIPRP::reset(const std::shared_ptr
<ReplacementData
>& replacement_data
) const
75 std::shared_ptr
<BRRIPReplData
> casted_replacement_data
=
76 std::static_pointer_cast
<BRRIPReplData
>(replacement_data
);
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;
84 casted_replacement_data
->rrpv
= maxRRPV
;
89 BRRIPRP::getVictim(const ReplacementCandidates
& candidates
) const
91 // There must be at least one replacement candidate
92 assert(candidates
.size() > 0);
94 // Use first candidate as dummy victim
95 ReplaceableEntry
* victim
= candidates
[0];
97 // Store victim->rrpv in a variable to improve code readability
98 int victim_RRPV
= std::static_pointer_cast
<BRRIPReplData
>(
99 victim
->replacementData
)->rrpv
;
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
;
107 // Stop searching for victims if an invalid entry is found
108 if (candidate_RRPV
== maxRRPV
+ 1) {
110 // Update victim entry if necessary
111 } else if (candidate_RRPV
> victim_RRPV
) {
113 victim_RRPV
= candidate_RRPV
;
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
;
121 // No need to update RRPV if there is no difference
123 // Update RRPV of all candidates
124 for (const auto& candidate
: candidates
) {
125 std::static_pointer_cast
<BRRIPReplData
>(
126 candidate
->replacementData
)->rrpv
+= diff
;
133 std::shared_ptr
<ReplacementData
>
134 BRRIPRP::instantiateEntry()
136 return std::shared_ptr
<ReplacementData
>(new BRRIPReplData(maxRRPV
));
140 BRRIPRPParams::create()
142 return new BRRIPRP(this);