1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
|
/**
* Copyright (c) 2018 Inria
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Daniel Carvalho
*/
/**
* @file
* Definitions of a Tree-PLRU replacement policy, along with some helper
* tree indexing functions, which map an index to the tree 2D-array.
*/
#include "mem/cache/replacement_policies/tree_plru_rp.hh"
#include <memory>
#include "base/intmath.hh"
#include "params/TreePLRURP.hh"
/**
* Get the index of the parent of the given indexed subtree.
*
* @param Index of the queried tree.
* @return The index of the parent tree.
*/
static uint64_t
parentIndex(const uint64_t index)
{
return std::floor((index-1)/2);
}
/**
* Get index of the subtree on the left of the given indexed tree.
*
* @param index The index of the queried tree.
* @return The index of the subtree to the left of the queried tree.
*/
static uint64_t
leftSubtreeIndex(const uint64_t index)
{
return 2*index + 1;
}
/**
* Get index of the subtree on the right of the given indexed tree.
*
* @param index The index of the queried tree.
* @return The index of the subtree to the right of the queried tree.
*/
static uint64_t
rightSubtreeIndex(const uint64_t index)
{
return 2*index + 2;
}
/**
* Find out if the subtree at index corresponds to the right or left subtree
* of its parent tree.
*
* @param index The index of the subtree.
* @return True if it is a right subtree, false otherwise.
*/
static bool
isRightSubtree(const uint64_t index)
{
return index%2 == 0;
}
TreePLRURP::TreePLRUReplData::TreePLRUReplData(
const uint64_t index, std::shared_ptr<PLRUTree> tree)
: index(index), tree(tree)
{
}
TreePLRURP::TreePLRURP(const Params *p)
: BaseReplacementPolicy(p), numLeaves(p->num_leaves), count(0),
treeInstance(nullptr)
{
fatal_if(!isPowerOf2(numLeaves),
"Number of leaves must be non-zero and a power of 2");
}
void
TreePLRURP::invalidate(
const std::shared_ptr<ReplacementData>& replacement_data) const
{
// Cast replacement data
std::shared_ptr<TreePLRUReplData> treePLRU_replacement_data =
std::static_pointer_cast<TreePLRUReplData>(replacement_data);
PLRUTree* tree = treePLRU_replacement_data->tree.get();
// Index of the tree entry we are currently checking
// Make this entry the new LRU entry
uint64_t tree_index = treePLRU_replacement_data->index;
// Parse and update tree to make it point to the new LRU
do {
// Store whether we are coming from a left or right node
const bool right = isRightSubtree(tree_index);
// Go to the parent tree node
tree_index = parentIndex(tree_index);
// Update parent node to make it point to the node we just came from
tree->at(tree_index) = right;
} while (tree_index != 0);
}
void
TreePLRURP::touch(const std::shared_ptr<ReplacementData>& replacement_data)
const
{
// Cast replacement data
std::shared_ptr<TreePLRUReplData> treePLRU_replacement_data =
std::static_pointer_cast<TreePLRUReplData>(replacement_data);
PLRUTree* tree = treePLRU_replacement_data->tree.get();
// Index of the tree entry we are currently checking
// Make this entry the MRU entry
uint64_t tree_index = treePLRU_replacement_data->index;
// Parse and update tree to make every bit point away from the new MRU
do {
// Store whether we are coming from a left or right node
const bool right = isRightSubtree(tree_index);
// Go to the parent tree node
tree_index = parentIndex(tree_index);
// Update node to not point to the touched leaf
tree->at(tree_index) = !right;
} while (tree_index != 0);
}
void
TreePLRURP::reset(const std::shared_ptr<ReplacementData>& replacement_data)
const
{
// A reset has the same functionality of a touch
touch(replacement_data);
}
ReplaceableEntry*
TreePLRURP::getVictim(const ReplacementCandidates& candidates) const
{
// There must be at least one replacement candidate
assert(candidates.size() > 0);
// Get tree
const PLRUTree* tree = std::static_pointer_cast<TreePLRUReplData>(
candidates[0]->replacementData)->tree.get();
// Index of the tree entry we are currently checking. Start with root.
uint64_t tree_index = 0;
// Parse tree
while (tree_index < tree->size()) {
// Go to the next tree entry
if (tree->at(tree_index)) {
tree_index = rightSubtreeIndex(tree_index);
} else {
tree_index = leftSubtreeIndex(tree_index);
}
}
// The tree index is currently at the leaf of the victim displaced by the
// number of non-leaf nodes
return candidates[tree_index - (numLeaves - 1)];
}
std::shared_ptr<ReplacementData>
TreePLRURP::instantiateEntry()
{
// Generate a tree instance every numLeaves created
if (count % numLeaves == 0) {
treeInstance = new PLRUTree(numLeaves - 1, false);
}
// Create replacement data using current tree instance
TreePLRUReplData* treePLRUReplData = new TreePLRUReplData(
(count % numLeaves) + numLeaves - 1,
std::shared_ptr<PLRUTree>(treeInstance));
// Update instance counter
count++;
return std::shared_ptr<ReplacementData>(treePLRUReplData);
}
TreePLRURP*
TreePLRURPParams::create()
{
return new TreePLRURP(this);
}
|
